OKPARA, MORGAN OBINNAs Project Corrected... · than subsequent eggs laid in a clutch, while the first eggs in a clutch for Nera black were greater than other eggs in the clutch, although

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OKPARA, MORGAN OBINNA

LAYING AND PHYSICAL CHARACTERISTICS OF SHAVER BROWN

AND NERA BLACK HENS IN HOT HUMID ENVIRONMENT

FACULTY OF AGRICULTURE

DEPARTMENT OF ANIMAL SCIENCE,

kkdkjd

NWANKWO ONYEKACHI.A.

2

TITLE PAGE

LAYING AND PHYSICAL CHARACTERISTICS OF SHAVER BROWN AND

NERA BLACK HENS IN HOT HUMID ENVIRONMENT

BY

OKPARA, MORGAN OBINNA

PG/MSc/09/50547

A THESIS SUBMITTED TO THE DEPARTMENT OF ANIMAL SCIENCE,

FACULTY OF AGRICULTURE IN FUFILLMENT OF THE REQUIREMENT

FOR THE AWARD OF MASTER OF SCIENCE DEGREE OF THE

UNIVERSITY OF NIGERIA, NSUKKA.

AUGUST, 2012

3

CERTIFICATION

This is to certify that the work embodied in this project report for the degree

of Master of Science of the University of Nigeria, Nsukka was carried out by Mr.

Okpara, Morgan Obinna at the Poultry Farm of the Animal Science Department of

this University. The work presented herein is original and has not been submitted

in part or full for any other degree of this or any other university

……………………………………….. …………………………

DR. A.O. ANI Date

Project Supervisor

……………………………………….. ………………………...

DR. A.E. ONYIMONYI (Esq.) JP Date

Head of Department

……………………………………….. …………………………

EXTERNAL EXAMINER Date

4

DEDICATION

This work is dedicated to my beloved family and to God Almighty, our Father in

heaven.

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ACKNOWLEDGEMENT

I wish to sincerely record in the pages of history the unalloyed cooperation I

received from my research supervisor Dr. A.O. Ani. He sponsored the research and

provided a fertile ground for the successful completion of the work.

I am grateful to the Head of Animal Science Department, Dr. A.E.

Onyimonyi. I would also like to express my profound gratitude to Professor A.G.

Ezekwe, Professor S.O.C. Ugwu, Dr. N.S. Machebe, Dr. (Mrs) H.M. Ndofor-

Foleng, Miss N.C.P. Uberu and Mr. C.O. Osita. I thank Dr. C.C. Ogbu for his

assistance in the statistical analysis of the data and for his invaluable contribution

during and after the research work.

I thank Dr. E.C. Akanno of the Center for Genetic improvement of

Livestock, Department of Animal and Poultry Science, University of Guelph,

Ontario Canada, for his contribution towards my academic and mental

emancipation during the study.

The Farm Manager, Mr. S.C. Chime provided a very conducive environment

on the farm for my study to sail through.

My thanks are due to Mr. Mark Nnamani for assisting and guiding me

during the study.

Finally, I thank the Almighty GOD for His grace and blessings without

which this programme would have been impossible. To Him I say “Thus Far the

Lord has helped me”. Many thanks to all and may GOD bless all of you.

6

TABLE OF CONTENTS

Title Page .. .. .. .. .. .. .. .. .. i

Certification .. .. .. .. .. .. .. .. ii

Dedication .. .. .. .. .. .. .. .. .. iii

Acknowledgement .. .. .. .. .. .. .. iv

Table of contents .. .. .. .. .. .. .. v

List of Tables .. .. .. .. .. .. .. .. viii

List of figures .. .. .. .. .. .. .. .. ix

Abstract .. .. .. .. .. .. .. .. .. x

CHAPTER ONE

Introduction

1.1 Background .. .. .. .. .. .. .. 1

1.2 Statement of problem .. .. .. .. .. 3

1.3 Objectives of study .. .. .. .. .. 3

1.4 Justification of study .. .. .. .. .. 4

CHAPTER TWO

Literature Review

2.1 Classification of chickens .. .. .. .. .. 5

2.2 Exotic breed of laying birds .. .. .. .. .. 5

2.3 The reproductive system of the laying hen .. .. 6

2.3.1 The Ovary .. .. .. .. .. .. .. .. 7

2.3.2 The Oviduct .. .. .. .. .. .. .. 8

2.3.3 Ovulation .. .. .. .. .. .. .. .. 9

2.3.4 Egg formation .. .. .. .. .. .. .. 12

2.4 Oviposition .. .. .. .. .. .. .. 12

2.4.1 Sequential laying .. .. .. .. .. .. 13

2.4.2 Sequence/Clutch length .. .. .. .. .. .. 15

2.4.3 Pause days .. .. .. .. .. .. .. 15

2.4.4 Ovpiosition time .. .. .. .. .. .. .. 16

2.4.5 Time interval between successive eggs and lag .. .. 16

2.4.6 Total egg production .. .. .. .. .. .. 17

2.4.7 Rate/Intensity of lay .. .. .. .. .. .. 17

2.5 Egg quality .. .. .. .. .. .. .. 18

2.5.1 Egg weight .. .. .. .. .. .. .. 19

2.6 Physical characteristics of hens .. .. .. .. 19

2.7 Climatic condition .. .. .. .. .. .. 21

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CHAPTER THREE

Materials and Methods

3.1 Location and duration of study .. .. .. .. .. 23

3.2 Experimental birds .. .. .. .. .. .. 25

3.3 Management of hens .. .. .. .. .. .. 25

3.4 Parameters measured .. .. .. .. .. 25

3.4.1 Oviposition time .. .. .. .. .. .. 25

3.4.2 Total egg production .. .. .. .. 25

3.4.3 Clucth/sequence length .. .. .. .. .. 26

3.4.4 Pause days .. .. .. .. .. .. .. 26

3.4.5 Egg weight .. .. .. .. .. .. .. 26

3.4.6 Egg quality .. .. .. .. .. .. .. 26

3.4.7 Average daily feed intake .. .. .. 27

3.4.8 Percentage egg production .. .. .. 27

3.5 Physical characteristics .. .. .. .. .. .. 27

3.6 Temperature .. .. .. .. .. .. .. .. 28

3.7 Experimental design .. .. .. .. .. .. ..

3.8 Statistical analysis .. .. .. .. .. .. .. 28

CHAPTER FOUR

Results and discussion

4.1 Results

4.1.1 Egg laying characteristics of Shaver brown hens .. 29

4.1.1.1 Oviposition time .. .. .. .. .. .. .. 29

4.1.1.2 Total egg production .. .. .. .. .. .. 31

4.1.1.3 Clutch length .. .. .. .. .. .. .. 31

4.1.1.4 Pause days .. .. .. .. .. .. .. .. 37

4.1.1.5 Egg weight .. .. .. .. .. .. .. .. 37

4.1.1.6 Intensity/ Rate of lay .. .. .. .. .. .. 37

4.1.1.7 Hen housed egg production (HHEP) .. .. .. .. 39

4.1.1.8 Hen day egg production (HDEP) .. .. .. .. 39

4.1.2 Egg laying characteristics of Nera black hens .. .. 41


4.1.2.2 Total egg production .. .. .. .. .. .. 43

4.1.2.3 Clutch length .. .. .. .. .. .. .. 43

4.1.2.4 Pause days .. .. .. .. .. .. .. .. 50

4.1.2.5 Egg weight .. .. .. .. .. .. .. 50

4.1.2.6 Intensity/ Rate of lay .. .. .. .. .. 50

4.1.2.7 Hen housed egg production (HHEP) .. .. .. 51

4.1.2.8 Hen day egg production (HDEP) .. .. .. 51

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4.1.3 Effect of temperature on performance of Shaver brown

and Nera black hens .. .. .. .. .. .. 55

4.1.4 Interaction of strain and temperature on Performance .. 57

4.1.5 Physical characteristics of hens .. .. .. .. 57

4.1.6 Comparison between strains for performance and egg

quality traits .. .. .. .. .. .. .. .. 58

4.2 Discussion

4.2.1 Climatic data for Nsukka .. .. .. .. .. .. 60

4.2.2.1 Egg laying characteristics of Shaver brown

and Nera black hens .. .. .. .. .. 60


4.2.2.2 Total egg production and other egg productionIndices .. 61

4.2.2.3 Clutch length .. .. .. .. .. .. .. 61

4.2.2.4 Pause days .. .. .. .. .. .. .. .. 62

4.2.2.5 Egg weight .. .. .. .. .. .. .. .. 62

4.2.3 Effect of temperature on performance of Shaver

brown and Nera black hens .. .. .. .. 63

4.2.4 Interaction of strain and temperature on performance .. 65

4.2.5 Physical characteristics .. .. .. .. .. .. 67

4.2.6 Comparison between strains for performance and egg

quality traits.. .. .. .. .. .. .. .. 69

CHAPTER FIVE

Summary and conclusion .. .. .. .. .. .. 71

References .. .. .. .. .. .. .. .. .. 72

Appendices .. .. .. .. .. .. .. .. 81

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LIST OF TABLES

Table 1: Times of egg laying in hens .. .. .. .. .. .. 14

Table 2: Mean weekly environmental temperatures and relative humidity during

the period of the study.. .. .. .. .. .. .. 24

Table 3: Frequency distribution of egg production of Shaver brown hens .. 30

Table 4: Frequency distribution of mean clutch length of Shaver brown hens 32

Table 5: Effect of egg position and clutch size on egg weight of Shaver brown hens 33

Table 6: Frequency distribution of pause days of Shaver brown hens 34

Table 7: Effect of oviposition interval on egg weight of Shaver brown hens.. 36

Table 8: Frequency distribution of egg laying of Shaver brown and Nera

black hens during the day .. .. .. .. .. .. 38

Table 9: Classification of experimental hens .. .. .. .. .. 40

Table 10: Frequency distribution of egg production of Nera black hens .. 42

Table 11: Frequency distribution of mean clutch length of Nera black hens .. 44

Table 12: Effect of egg position and clutch size on egg weight of Nera black hens 45

Table 13: Frequency distribution of pause days of Nera black hens .. .. 46

Table 14: Effect of oviposition interval on egg weight of Nera black hens .. 49

Table 15: Comparison between strains for performance and egg quality traits 52

Table 16: Effect of temperature on performance of Shaver brown hens .. 63

Table 17: Effect of temperature on performance of Nera black hens 54

Table 18: Effect of interaction of strain and temperature on performance 56

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LIST OF FIGURES

Figure 1: Frequency distribution of egg laying of Shaver brown hens

at different oviposition intervals during the day .. .. 35

Figure 2: Frequency distribution of egg laying of Nera black hens

at different oviposition intervals during the day .. .. 47

Figure 3: Average weekly temperatures (Indoor and Outdoor) and relative

humidity of the study area .. .. .. .. .. 48

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ABSTRACT

A total of one hundred and fifty Shaver brown and Nera black hens in their 14th

week of lay were

used in a study conducted to determine the laying and physical characteristics of Shaver brown

and Nera black hens under humid tropical environment. Hens were housed individually in

separate cages. The hens were supplied water ad libitum and fed layers mash containing 16.5%

crude protein and 2650 kcal/kg of metabolizable energy for 10 weeks. The hens were also

divided into three classes based on their laying performance as follows: good layers, intermediate

layers and poor layers and their physical conditions appraised. Temperature readings were taken

3-hourly at time intervals of 0900h, 1200h, 1500h, and 1800h using a standard air thermometer

and the mean daily temperatures noted. The climatic data taken during the period of the

experiment showed that the study area had the natural day-length of 13 to 14 hours; mean

maximum weekly indoor and outdoor temperatures of 27.90C to 29.2

0C and 26.8

0C to 30.5

0C,

respectively; mean minimum weekly indoor and outdoor temperatures of 20.50C to 22.3

0C and

20.00C to 23.60

0C, respectively; relative humidity of 73.1% to 76.6% and mean total monthly

rainfall of 781.33mm. Results showed that the peak of lay was between 0700h and 0800h and

declined gradually throughout late afternoon hours until no egg was laid between 1700h and

1800h. For Shaver brown hens, about 86.24% and 13.76% of the eggs were laid in the morning

and afternoon hours respectively, while 88.75% and 11.25% of the eggs were laid in the morning

and afternoon hours respectively, for Nera black hens. Mean egg weight of 70.05g±1.07 and

70.10g±0.92 for eggs laid between 0600h and 0700h for Shaver brown and Nera black hens,

respectively were the heaviest (P<0.05) of all the mean egg weights observed in all oviposition

intervals. For Shaver brown hens, first eggs laid in a clutch were significantly greater (P<0.05)

than subsequent eggs laid in a clutch, while the first eggs in a clutch for Nera black were greater

than other eggs in the clutch, although the differences were not significant (P>0.05). Hens with

the longest clutches and shortest number of pause days produced the greatest number of eggs.

The total number of pause days observed were 1410 and 1329 for Shaver brown and Nera black

hens, respectively. Observations made on physical characteristics of the hens revealed that good

layers had smooth combs and wattles, moist and enlarged vents with flexible pubic bone, soft

abdomen and worn out feathers. Intermediate layers had similar features with good layers except

that the eye rings, beaks and shanks were slightly bleached. Poor layers had dry combs and

wattles, tight and hard abdomen and closed pubic bones. The Effect of ambient temperature on

performance parameters showed that for Shaver brown hens, hen day egg production, average

daily feed intake, egg shell weight, egg shape index, albumin height, yolk height, yolk height and

Haugh units were significantly reduced (P<0.05) with increasing temperatures. All performance

parameters measured for Nera black hens were significantly reduced (P<0.05) with increasing

temperatures. Likewise, there was significant interaction (P<0.05) of strain and temperature on

average daily feed intake and yolk height. The results of the present study indicate that although

heat stress had effect on performance, Shaver brown and Nera black hens are adapted to humid

tropical environment and can lay 86.24% and 88.75% eggs, respectively in the morning hours,

with overall production rate of 66.43% and 68.36% respectively, for Shaver brown and Nera

black hens.

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CHAPTER ONE

INTRODUCTION

1.1 BACKGROUND OF THE STUDY

The growth in global demand for poultry products is tremendous as the market for these products

is growing very fast. Poultry is probably the fastest route to achieve any appreciable

improvement in the nutritional standard of the populace because of its short generation interval,

quick turnover rate and relatively low capital investment (Smith, 2001; Ani and Okeke, 2011).

Gueye (2000) asserted that 85% of rural households in Sub-Saharan Africa keep chickens or

other types of poultry. Poultry are equally important to other smallholders in Asia, Latin America

and other parts of the world (Mallia, 1999; FAO, 2003; Islam and Jabbar, 2005; Kyrsgarrd,

2007). Increased egg production is one sure way of achieving the target of providing quality

animal protein at a minimum cost to the consumers (Oluyemi and Roberts, 2000). Advances in

genetic selection make today’s commercial layers quite different from those of years ago. Body

weight is less, age at housing is earlier, total egg number has increased, egg mass is greater and

feed conversion has improved considerably (Miles and Jacob, 2000; Minivielle et al., 2006).

Total egg production is affected both by the physical and laying characteristics of the hen.

Laying characteristics of hens have been assessed by evaluating such indices as rate of lay,

oviposition time, clutch/sequence length, number of pause days, lag time, hen housed egg

production (HHEP), and hen day egg production (HDEP).

Physical characteristics of laying hens on the other hand, consist of those features that can be

seen easily on their body such as condition of combs, wattles, eyes, beaks, pubic bones, abdomen

and vent. They are used to determine whether a hen is laying or not (Gillespie, 1997; Reddy et

al., 2004; Daghir, 2008; Ani and Nnamani, 2011).

Apart from egg laying characteristics which are cyclic and genetically influenced, egg

production is affected by nutrition, variations in temperature, light intensity, day- length, relative

humidity, disease and level of management. Hens lay sequentially (Wolford et al., 1997;

Spradbrow, 1997; Gillespie, 1997; Miles and Jacob, 2000; Smith, 2003; Van Der Molen, 2004;

Jakowski and Kaufman, 2004; Reddy et al., 2004; Clauer, 2005; Poultryhelp, 2005). Hens vary

in their laying habits. The number of eggs in a sequence varies between one to forty and

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occasionally even more. Even if flock uniformity is high, not all hens in the flock lay at the same

rate. While some hens may be laying at a very high rate of production, others may not even be

laying at all (Miles and Jacob, 2000; Ani and Nnamani, 2011). The longer the clutch length, the

more eggs a hen lays in a given period (Etches, 1996; Reddy et al., 2004; Jakowski and

Kaufman, 2004 ). According to Butcher and Miles (2000), the exotic hen is capable of laying

240-270 eggs per annum, each weighing about 58 grammes under tropical condition. The

success of birds as a class is largely due to the fact that they have evolved physiological

mechanisms that cause them to lay eggs at a time of season, when such factors as weather and

food supply are optimal (Koelkebeck, 2001). According to Daghir (2008), humid environment is

very suitable for poultry production. Although all livestock are subject to environmental stress in

the tropics, poultry appears to be less susceptible than mammals. One reason may be that with

higher body temperature than mammals, birds spend less production energy than other livestock

in homeostatic regulations (adjustments). Under suitable tropical housing and management

practices, poultry performance in the tropics has in many instances compared favourably with the

performance standards of the same breeds reared in temperate environments. In acclimatizing to

hot climate, animals normally make physiological adjustments (Hahn et al., 2003). As the

seasons change, two major kinds of changes occur in the environments: changes in temperature

and changes in length of daylight. Hormones enable the animal to respond physiologically to

these seasonal changes (Hahn et al., 2003). The pineal body in chicken’s brain controls its body

temperature and its sense of environmental temperature. Normal body temperature lies between

39.80C and 43.6

0C being at its highest around 1600h and its lowest around midnight (Hahn et al.,

2003; Daghir, 2008). Egg production is intimately linked with daylight hours. The light rays

received through the eyes affect the pituitary gland, which releases hormone into the bloodstream

thus stimulating the ovaries into action. As the day-length hours shorten, egg production

correspondingly decreases. By midwinter in temperate environment, it is usually nonexistent. To

ensure continued production, hens in temperate regions must have a minimum of 16 hours of

light per day. As the hours of natural day-length decreases, artificial lighting can be gradually

introduced for longer periods to make up the difference (Clauer, 2005; Hanson, 2005).

Environmental condition of the area in which the hens are laying affects their sequence length.

1.2 STATEMENT OF PROBLEM

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Advances in genetic selection make today’s commercial layers quite different from those of

years ago. Body weight is less, age at housing is earlier, total egg number has increased, egg

mass is greater and feed conversion ratio has improved considerably (Miles and Jacob, 2000;

Minivielle et al., 2006). Although management and feeding practices are the key determining

factors of egg production, the breed of laying hen affects egg production. The rate of adaptation

and quality of egg production of different exotic breeds of hen vary when exposed to a variety of

climate and environments. According to Miles and Jacob (2000), some hens may be laying at a

very high production rate while others may not be laying at all. The climatic conditions of

Nsukka in particular and those of South Eastern Nigeria in general depict a typical tropical

climate (Egbunike, 2002). Findings by Okonkwo and Akubuo (2007) have revealed an average

annual minimum and maximum temperature ranges of 220C

- 24.7

0C and 33

0C -37

oC,

respectively. These ranges appear to fall outside the zone of thermo neutrality of laying hens

which is 180C

- 22

oC as recently defined by Imik et al. (2009). As such, adverse effects of heat

stress are suspected to clasp egg production parameters of laying hens in the tropics. Most

African diets (including Nigerian) are deficient in animal protein which results in poor and

stunted growth as well as increase in spread of diseases and consequently death (Apantaku et al.,

2003). Apart from low egg production and poor performing breeds, other problems associated

with poultry production in Nigeria are diseases and pests, poor weight gain/feed conversion,

feeding and management problems and lack of capital (Eekeren et al.,1995; Isiaka 1998;

Apantaku et al., 2003). Moreover, the environment to which poultry birds are exposed affect

performance of the birds (Abeke et al., 1998; Isiaka, 1998). The optimal laying temperature is

between 18-220C (Imik et al., 2009), while a relative humidity above 75 percent will cause a

reduction in egg laying (Hahn et al., 2003). When the temperature rises above 280C

, the

production and quality of eggs decrease as seasonal temperature increase can reduce egg

production by 10 percent (Oluyemi and Roberts, 2000; Smith, 2001). Lastly, egg

production clearly requires planning for costs as well as for profit generation and for meeting

market demand without which a commercial egg production venture may suffer serious setbacks.

1.3 OBJECTIVES OF THE STUDY

The study was aimed at evaluating the laying and physical characteristics of Shaver brown

and Nera black hens in hot humid environment.

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The specific objectives of the study were as follows:

1. To determine the oviposition time, and clutch size of Shaver brown and Nera black hens

in hot humid environment.

2. To determine position of eggs in a clutch and their relationship to egg weight in hot

humid environment.

3. To determine the comparative performance of Shaver brown and Nera black hens in hot

humid environment.

4. To establish the relationship between performance and environmental temperature.

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1.4 JUSTIFICATION OF THE STUDY

With the increasing importation and utilization of exotic hybrids in commercial egg production

in Nigeria, it is imperative to study the egg laying characteristics of these birds under the local

condition. Information obtained would help assess the level of adaptability of Shaver brown

and Nera black hens to humid tropical environment. Knowledge of laying distribution is

necessary in recommending frequency of egg collection to management and poultry farmers.

More eggs crack if they are not collected at frequent intervals. When buying birds at the point

of lay, a careful observation of the physical features will enable a farmer to choose or buy only

birds that have the potential of good layers. The ultimate objective of the poultry farmer is the

realization of profit, and in order to do this, he must understand the interactions between body

conformation, body function and environment. In the tropical context, environment (mainly

temperature and humidity) plays a very important role as it imposes extra stress in the ability of

the chicken to grow and function optimally. Solutions to the problems bedeviling poultry

production in Nigeria depend mostly on research and this requires effective research approach

to make meaningful impact on poultry productivity. At this juncture therefore, conducting

research on the laying and physical characteristics of two strains of exotic breed of hen has

become imperative so as to obtain information that would help in assessing their level of

adaptability to humid tropical environment and also, to establish proven production basis

which will determine their suitability and adaptability for massive commercial and small scale

egg productions.

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CHAPTER TWO

LITERATURE REVIEW

2.1 CLASSIFICATION OF CHICKEN

There are approximately 175 varieties of chickens grouped into 12 classes and

approximately 60 breeds (Daghir, 2008; Obioha, 1992). A class is a group of breeds

originating in the same geographical area. The names themselves – Asiatic, American,

Mediterranean, indicate the region where the breeds originated.

Breed means a group which possesses a given set of physical features, such as body

shape, skin colour, carriage or station, and number of toes.

Variety is a category of breed and is based on feather colour, comb or presence of beard

or muff. Thus the Plymouth Rock may be Barred, White, Buff or one of other several colours.

The Rhode Island Red may be either a single or rose comb. In each case, the body shape and

physical features should be identical. Breed and Variety tell little about the qualities of good

producing stock. Strain however, does. A strain is a group of breeding population within a

variety or cross that has been bred and developed to possess certain desirable characteristics.

Many commercial strains exist such as Babcock, Dekalb, Hyline, and Shaver that have been

bred for specific purposes mainly for egg production (Daghir, 2008).

2.2 Exotic breeds of laying birds

The first exotic chickens to be imported into Nigeria probably came around the early

fifties but their full commercial potential was not realized until the late fift ies after their

successful adaptation and performance.

The earliest breeds which were imported then included Rhode Island Red, Barred

Plymouth Rock, New Hampshire and White Leghorn. Although these came as straight breeds,

their ancestors were composite of different blood lines which had been developed in the native

or adapted countries from several generations of crosses. Subsequent importation included

several hybrids developed from inbred lines and cross-breeding processes aimed at developing

strains for growth or egg production.

The more common hybrids in tropical Africa today according to Daghir (2008) and Obioha

(1992) include:

A UNITED STATES

1 Hyline / B 11

18

2 Hyline 935

3 Harco (Obioha, 1992)

4 Babcock 300

5 Babcock 380

B UNITED KINGDOM

1. Rangers/Sykes

2. Thornbers 808

3. Thornbers 909

C FRANCE

1. Warren Sex-Linked

D CANADA

1. Shaver Star Cross

2. Shaver Star Cross 444T

3. Brown Eggs Shaver 579 ( intensive and alternative)

E ISRAEL

1 Yarkon

2 Yaafa

3 Kabir (Obioha, 1992).

These Layers have variable performance capabilities, and because of the rapid genetic

turnover by breeders, new strains appear in the market practically everyday (Obioha, 1992).

The best chicken breeds include commercial white-type hybrids, which produce white-shelled

eggs and are the most economical feed to egg converter.

Commercial red plumage coloured birds (e.g. Rhode Island Reds, New Hampshire) or

sex linked hybrids produce large, brown-shelled eggs. These birds have meaty carcasses and

produce a good supply of eggs. The hybrids that lay more eggs tend to be docile than those that

lay white eggs. All poultry breeds lay eggs, but they are not equally efficient (Clauer, 2005).

2.3 The Reproductive System Of Hen

There are two main parts of the reproductive system of hen: the ovary and the oviduct.

Only the left ovary and the oviduct develop in a bird (Imai, 2003; Pineda and Dooley, 2003).

Pesek (1999) noted that right ovary regressed probably as an adaptive mechanism to

reduce weight necessary to aid flight. The ovary is attached underneath the backbone, about

midway between the neck and tail. When a female chick is hatched, the ovary begins to

19

convert ova to egg yolks at the appropriate time. For this to happen, the pullet (young female

chicken) must have reached the correct stage of physical development. Then if the appropriate

light stimulation is present, hormones cause ova to develop in sequence to yolks.

Yolks are released from the ovary into the body cavity when they reach the correct size

(Smith, 1998). The ovulated yolk is retrieved by the infindubulum, the first part of the oviduct.

Completion of the egg will require approximately 24 or more hours. Passage through the

magnum, isthmus and uterus of the oviduct results in the addition of egg white, shell

membrane and shell.

Soon after an egg is laid (oviposition), the process starts again. Another yolk is

released, and the next egg formed. Some chicken and ducks can lay an egg everyday for more

than 300 consecutive days. Other birds, may lay only a few eggs, yet others may lay only every

second day (Smith, 1998).

2.3.1 The Ovary

The ovary is located in the body (abdominal cavity), ventral to the aorta, posterior to

the vena cava, and cranial to the kidney. At hatch, the ovary of a chick contains many

thousands of follicles (oocytes) each of which has the potential to become the yolk of an egg.

Given the opportunity, hens from highly selected strains may lay 2000-3000 eggs during their

life expectancy of 7-10 years (Zakaria, 2001; Etches, 1996).

At the time of sexual maturity, (18 to 20 weeks of age), 4 to 6 oocytes increase in

diameter and the follicular hierarchy begins to be established. During subsequent ovulation

cycle, only the largest follicle will ovulate followed in successive days by the 2nd

, 3rd

, 4th

largest ones, each of which enlarges to assume the size of the ovulated predecessor (Etches,

1996). Cassey et al. (2004) noted that in hens, the ovarian follicles committed to ovulation are

arranged in an orderly follicular hierarchy. The ovary of the mature hen contains a hierarchy of

yellow yolky follicles and several thousand smaller follicles from which the large yolk follicles

are recruited.

Esminger (1991) observed that at the time of hatching, the female chick’s left ovary

contains approximately 3,600 to 4,000 tiny ova from which fully-sized yolks may develop

when the hen matures. Austic and Nesheim (1990) reported that the ovary of a hen contains 5

to 6 large yellow developing yolks (follicles) and a large number of small large number of

small white follicles which represent immature underdeveloped yolks. Each of the follicles

contains an oocyte and it is attached to the ovary by a slender stalk called the stigma.

20

In the hierachy, Zakaria (2001) explained that sizes range from microscopic to size of

the follicle that is destined to ovulate next. This follicle weighs about 15g; the next member of

this size hierarchy weighs about 12g and the third about 10g. Below these sizes, there may be

several follicles less than 1mg, and eventually down to a multitude of follicles of microscopic

size. Only a follicle reaches ovulatory size each day. After ovulation of the longest follicle, the

smaller follicles move up one notch size and re-establish the hierarchy as it existed just before

ovulation.

Zakaria (2001) also threw some light into mechanisms involved in establishing and

maintaining follicular size hierarchy for prolonged period of time. He indicated that the hen

must be able to distribute hypophyseal hormones circulation in the bloodstream in such a way

that some follicles get a larger quantity of formed ones, so that they can grow faster and

become large, and other follicles receive a small quantity. The net result of the rationing

system is that they establish and maintain a follicular size hierarchy in which the position of

the individual follicle is determined by the amount of hormone stimulating it.

According to Etches (1996), most follicles therefore never ovulate, but it would appear

that most participate in the production of steroid hormones from the ovary. At an early stage of

follicular development that has not yet been identified, the small ovarian follicles begin to

produce oestrogen. As sexual maturity approaches, the production of these hormones

stimulates deposition of calcium in the medullary bone, development of yolk precursors by the

liver, development of the reproductive tract and development of other secondary

characteristics. These secondary characteristics include the comb, spurs, softening and

spreading of pubic bones and deposition of pigments in the beak, the shanks and around the

vent. Each of these secondary sexual characteristics can be, and is used to indicate both the

onset and maintenance of lay.

2.3.2 The Oviduct

An intimate anatomic relationship exists between the ovary and oviduct. The term

oviduct is used to describe the complete tubular genitalia of the hen. It is large, convoluted

tube occupying a large part of the abdominal cavity. It weighs about 60g in sexually mature

chicken and extends from ovary to cloaca (Zakaria, 2001). It has good blood supply and

muscular walls that are in nearly continuous movement during the time egg formation is

taking place. The oviduct is about 50-75cm long (Zakaria, 2001; Esminger, 1991). Austin and

Neshein (1990) noted that large variations occur in the size of the oviduct depending on the

21

stage of the reproductive cycle. The size changes are dependent upon the levels of the

gonadtrophic hormones being secreted by anterior pituitary and oestrogen production in the

ovary. The oviduct is divided into five clearly defined functional regions. Starting from the

ovarian end, they are infundubulum, the magnum, the isthmus, uterus or the shell gland and

vagina.

І The infundubulum (the funnel) picks up the ovulated egg. It is also the site of

fertilization.

ІІ The magnum is where the albumen is secreted

ІІІ The isthmus is where the shell membrane is secreted

ІV The uterus secretes the shell, adds fluid to the egg (plumping) and stratifies the

albumen

V The vagina stores sperm and aids in the expulsion of the full formed egg.

2.3.3 Ovulation

Ovulation is the release of the ovum from the ovarian follicles. It occurs through the

rupture of the follicles along streak called stigma (a specialized region of the follicle wall)

(Zakaria, 2001; Etches, 1996).

Ovulatory Cycle

The ovulatory cycle of hens is hormonally controlled by the subtle interaction of the

gonadotropins and ovarian steroid hormones. The ovulatory cycle of hens is defined as the

interval between consecutive ovulations. By subtraction of the consecutive times of ovulation,

the length of the ovulatory cycle reveals that they vary from a minimum of 25.12 hours to a

maximum of 28.53 hours within sequences of 2 to 6 eggs (Etches, 1996). The last ovulation of

a sequence is separated by approximately 40 hours from the first ovulation of the next

sequence because one full day elapses during which ovulation does not occur.

The minimum length of the ovulatory cycle of hens maintained under 14 hours of light

(14L: 10D) is therefore, 24 hours. This minimum is achieved by only a small proportion of

hens when the rate of lay is very high during peak production. In practice, it is technically

difficult to establish times of ovulation directly. Ovulation of the second and all subsequent

ova in a sequence however occurs 30-45 minutes after oviposition of the preceding egg and

this relationship is used to establish the time of ovulation (Etches, 1996).

22

An ovulatory cycle extends from the oviposition of the first egg of the next clutch.

Generally, the laying cycle of hen is governed by the lightning schedule. If the hen is given

12-14 hours of light per day, the first egg of the clutch is usually laid early in the morning. As

a rule, ovulation occurs shortly after oviposition (5-60 mins), and approximately 26 hours are

required before newly ovulated ovum acquires its integuments and is ready to be laid as an

egg (Zakaria, 2001). Because ovulation does not occur until after oviposition and because the

completion of the formation of the eggs requires at least 24 hours, each succeeding egg in the

clutch is laid later than the first egg of the clutch, the last egg of the clutch is laid early in the

afternoon. The hens with the longest clutches ovulate very shortly after oviposition and takes

less time (some only 24 hours) to complete the egg (Etches, 1996).

Under ordinary daylight conditions, ovulation occurs in the morning hours and almost

never after 3.00 pm. The ovulated egg spends about 3.5 hours in the magnum portion of the

oviduct where it acquires the albumen coat, 1.25 hours in the isthmus where the soft shell

membranes are formed and 21 hours in the uterus where the calciferous shell is applied. A

total of 25-26 hours is therefore required for egg formation. The succeeding egg is ovulated

30-60 minutes after the egg is oviposited (Jakowski and Kaufman, 2004).

Hormonal Control of Ovulation

The mechanisms controlling ovulation luteinizing hormone (LH) release, oviposition

and the eggs rate of travel through the oviduct have been worked out in part, but some details

remain unknown (Jakowski and Kaufman, 2004). Zakaria (2001) reported that the interval

between ovulation of two successive eggs is usually 24 to 28 hours. But the important

questions are , how is ovulation triggered? Why would a hen ovulate consecutively for several

days and then skip a day? And how are the intervals between ovulations kept at the stated

hours? According to Pineda and Dooley (2003), ovulation is brought about by the release of

the ovulatory (Luteinizing ) hormone from the pituitary gland governed by a timing

mechanism that is influenced by day length and the ovarian hormones.

Pesek (1999) suggested that follicular growth and maturation in the hen depends on a

constant output of follicle stimulating hormone (FSH) by the pituitary with based levels of

luteinizing hormone (LH). At the specific times during the ovulatory cycle, there is an

increased release of the LH which causes ovulation. An “excitation hormone” acts via the

neural pathway (hypolothamus) to trigger the LH release. The threshold for the action of the

23

“excitation hormone” undergoes diurnal fluctuations. If the level of the excitation hormone

reaches the threshold level necessary for LH release, the gonadotropin is released and

ovulation follows. Since successive follicles mature at intervals of 24 hours plus a lag (at a

later time each day), the increase in excitation hormone will follow a similar time course. As a

result, the neural components would be stimulated at a progressively later time each day until

eventually the peak level of the excitation hormone would occur at a time when the neural

threshold would also be elevated. Because the given concentration of the excitation hormone

was not sufficiently high to trigger the LH release, no ovulation would occur on that day and

there would be no pause in the ovulatory cycle. Luteinizing hormone would be stimulated

again the next day when the neural threshold for LH had decreased and ovulation would again

resume. The excitation hormone is generally assumed to be progesterone.

Zakaria (2001) indicated that it is very challenging to disentangle the hypothalamo-

hypophyseal-ovarian relationship in the hen because all the changes are compressed into 24-

26 hours ovulating cycle. Jakowski and Kaufman (2004) explained that there is experimental

evidence to show that the oviductal nervous system participates in signaling instructions to the

pituitary gland, and that instruction not to release amounts of gonadotropic hormones

adequate for ovulation may originate in the oviduct. Such signaling systems are frequently

involved in phenomena controlled by hormones and that they are part of the neuroendocrine

feedback mechanisms. In the hen, it seems to operate as follows: If a yolk is present in the

magnum, a nerve conducted signal goes from the oviduct preventing new ovulations from

occurring. Thus, no ovulatory dose of gonadotropic hormones would be released until the

oviduct is ready for the next egg. Soon after the egg leaves the oviduct and enters the uterus

(shell gland), these signals stop and the pituitary gland now releases the amount of

gonadotropic hormones needed to accomplish ovulation, some 8 to 12 hours later that is, after

the hard shelled egg is laid. As soon as the next ovum enters the oviduct, the ovulation

blocking signal action again becomes effective and holds further ovulation in check.

According to Hanson (2005), day length, temperature and humidity influence

reproduction. In areas where the climate is stable and day length is constant, rainfall may

trigger reproductive behaviour. Biological clocks known as “Circannual Cycles” control the

release of the hormones that regulate reproduction, metabolism and behaviour. Light

stimulates a part of the brain- the hypothalamus, to produce “releasing factors”. These

releasing factors stimulate the anterior pituitary to secrete hormones known as gonadotropins.

24

Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH) are two gonadotropins

produced by the anterior pituitary which affect the ovaries. FSH and, to a lesser degree, LH,

are responsible for normal ovarian follicular growth. As the follicle increases in size, they

produce increasing amounts of oestrogen and progesterone. Progesterone acts on LH which

triggers ovulation. Once ovulation occurs, progesterone secretion increases rapidly.

2.3.4 Egg Formation

According to Daghir (2008) and Obioha (1992), the egg is formed from an interaction

of hormonal, structural and nutritional process. The yolk forms in the ovary, its protein being

synthesized in and transported from the kidney and liver. The fat in the yolk is mainly dietary

or demobilized from fat deposits. Both fat and protein are transported by the blood. The yolk

material contains 35% fat, 17% protein and 50% water (Latour et al., 2003). According to

Latour et al. (2003), the formation of the egg involves the transport of large quantities of

material across numerous biological membranes, and the formation of many new substances,

particularly specific proteins and lipids. The size and the composition of the egg are affected

by numerous genetic environmental and physiologic factors. The passage of the egg down the

oviduct is made possible by peristalsis, probably aided to some extent by cilliary action.

According to BFREPA (2003), the original purpose of an egg was a protective development

chamber for an embryo to eventually produce a day old chick. Genetics and nutrition have led

to current layer strains, aimed more specifically at producing eggs for human consumption.

2.4 Oviposition

Oviposition (laying of the hen’s egg) is the expulsion of the fully calcified egg from the

reproductive tract. It requires coordination of the muscular activity of the shell gland with the

behavioural repertoire during which the hen investigates and selects a nest. Except for the last

oviposition of a sequence, expulsion of the egg is initiated by the pre-ovulatory endocrine

events that are associated with ovulation (Zakaria, 2001; Novo et al., 1997; Etches, 1996).

Oviposition is under both hormonal and neural control. The time of oviposition may be

determined by ovulation via changes in the ruptured follicle. The post ovulatory (ruptured)

follicle is necessary for oviposition because its removal delays oviposition (Novo et al.,

1997). It is not known precisely how oviposition is initiated, but both hormonal and neural

mechanisms are involved (Reddy et al., 2004). Whatever the stimulus, contraction of the

25

uterine musculature forces the egg into the vaginal region. This may be under neural

control, for stimulation of the central/nervous system can affect it, but hormones are also

involved.

Oviposition may also be regulated by the balance of the circulating steroid sex

hormones. Oluyemi and Roberts (2000) observed that progesterone is involved in ovulation.

Progesterone acts on the hormone-releasing factors in the hypothalamus to cause the release

for LH from the anterior pituitary which causes release of yolk from the ovary (Imai, 2003).

Johnson (1990) noted that in birds, ovulation and oviposition are processes controlled

by LH and sex steroids, including progesterone. Surges of LH and progesterone have been

observed between 4 and 7 hours before ovulation in laying chicken, quails and ducks and 2-8

hours before ovulation in laying turkey hens.

2.4.1 Sequential Laying

Chickens lay eggs in sequence or clutches. Normally the egg laying pattern follows

certain rules. The first rule is that egg of a sequence is laid within 1-2 hours after daylight.

Secondly, each egg in a sequence is laid later in the day. Thirdly, the last egg of a sequence is

typically laid about 9-10 hours after daylight as shown in Table 1.

26

Table 1: Sequence of egg laying in hens after daylight

Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7

9.05 13.30

8.44 11.26 15.15

8.01 10.00 12.03 15.23

7.24 9.22 10.26 11.46 15.05

7.33 9.20 10.34 11.30 12.34 15.40

7.45 9.12 10.10 10.51 11.39 12.38 15.26

(Robinson and Renema, 1999a; Etches, 1996).

27

Table 1 shows times of successive ovipositions under 14L:10D photoperiod. The last

ovulation of a sequence is followed by a day during which ovulation does not occur. According

to Etches (1996), birds can lay eggs for period of about 12 months without stopping. Birds can

lay up to 358 eggs in one year.

2.4.2 Clutch/Sequence Length

The number of eggs laid by a hen on consecutive days before a pause is known as a

clutch. A clutch is terminated a day an egg is not laid. A prolific hen lays five or more eggs in

a clutch, the clutches being separated by not more than a day of rest (pause). Clutches of 50-

100 eggs are not uncommon and many hens have laid 365 eggs in a year (Butcher and Miles,

2000). A hen laying 20, 30, or more eggs in one clutch accomplishes this by two means.

Shortening the interval between oviposition and ovulation to a few minutes (hens with very

long clutches ovulate even before the egg is laid) and/or shortening the time the egg spends in

the shell gland to as little as 18hours (Jakowski and Kaufman, 2004).

According to Robinson and Renema (1999b), the tendency of some hens to lay short

clutches (1 to 2 eggs) and others to lay longer clutches (6 and up to 100 or more) is a heritable

characteristic. Sequence length varies within birds of the same species depending on the cross

and probably, environmental conditions of the area in which the birds are laying.

Robinson and Renema (1999b), working on broiler breeder hens, observed that hens

have slow rate of follicular maturation (26-28hours or more) lay shorter (2-3 days) sequence.

On the other hand, hens that lay very long sequence typically have maturation rates of 24

hours or less. Sequence length changes throughout the egg production year with the longest

sequence seen at the time of peak production at about 30-35 weeks of age. All hens lay one

characteristically long sequence of eggs known as the “Prime Sequence” which in broiler

breeders is usually about 20 eggs in a length (Robinson and Renema, 1999b).

2.4.3 Pause (Skip days)

Pause is defined as the time between two clutches in which the hen is considered a low

producer. Pause may be due to environmental or genetic factors. The number of eggs in a

clutch and the number of pause days between clutches can be regular or irregular. Robinson

and Renema (1999b) illustrated this using data on white leghorn pullets:

Hen 1 00-00-00-two-egg cycle

Hen 2 000-000-000-three-egg cycle

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Hen 3 000-000-000 Regular Sequence, Regular Skip

Hen 4 00-000-0-000-Irregular Sequence, Regular Skip

Hen 5 00-000-0---- Irregular Sequence, Irregular Skip

“0” represents an egg while “-” represents a pause day.

2.4.4 Oviposition Time

Oviposition time is the actual time of the day in which an egg is laid. Under optimal

lighting conditions (usually 12-14 hours), a hen usually lays its first egg in the sequence in the

early hours of the morning and subsequent eggs are laid progressively later in the day. The

time of the day during which the hen lay most of their eggs is referred to as oviposition peak

period. This period falls in the morning hours in the domestic fowl. The actual time of the day

when eggs are laid depends on the length of the sequence and the position of the egg in the

sequence and also on the number of hours of daylight. Time of laying may also be influenced

by feeding schedule (Herren, 1994). If hens receive no light cues by being kept under

continuous light with natural daylight excluded and are fed only from 8am-4pm, most of the

eggs will be laid within those hours. On the other hand, if feeding is from 8pm to 4am, the

hens will adjust to the new schedule by laying most of their eggs during the new feeding

period (Herren, 1994).

2.4.5 Time Interval between successive eggs and lag

The difference between interval length of one egg and 24 hours is termed “lag”. The lag

or the interval between successively laid eggs in a sequence appears to be greater for the first

two or last two laid eggs of the sequence than those of the intervening eggs, length of the

sequence not withstanding. With average hens laying about 3-4 eggs per clutch, the interval is

about 26 hours. Such hens may lay first egg of clutch at 9am, the second at 11am, and third at

1pm and perhaps fourth at 3-4 pm.

As hens do not normally ovulate after 2pm, no ovulation will occur on fourth day resulting

in no egg laid on fifth day and a four-egg clutch will be terminated. The oviposition interval

by most hens range from 24-28 hours (Zakaria, 2001). Robinson and Renema (1999b) also

reported that “lag” is greater between the first and second egg in the clutch, then decreases

towards the end of the cycle. However, negative “lag” occurs in the middle of long cycles and

under such condition the interval between eggs is less than 24 hours. “Lag” again increases

towards the end of a sequence. This interval between eggs and the rhythm of lay mainly

29

represents difference in time of ovulation. “Lag” does not represent difference in time of

day of one oviposition with respect to its predecessor.

2.4.6 Total Egg Production

Total egg production is an attribute of the number and length of clutches, the duration

of the laying period, the rate of lay, number of pause days and length of broody period. Total

egg production is often calculated by a method which includes the effect of mortality. The

method involves dividing the total number of eggs laid during a period by the number of hens

or pullets housed at the beginning of the period. This gives a value known as hen-housed

average or production index.

The problem in this method is that high mortality during the period will lower the

value even though the surviving hens may have laid exceedingly well. Reddy et al. (2004)

modified the hen-housed method by replacing it with survivor egg production as one of egg

production indices. Survivor egg production is calculated by dividing the total number of eggs

laid by the number of surviving birds. It can be expressed in percentage.

According to Ani and Nnamani (2011), if a hen lays in clutches of single eggs, the most

she can lay in a thirty-day period is 15 eggs. If she lays 2-egg clutches, her maximum record

in 30 days is 20 eggs, an increase of 33.5%, where she lays in 3-egg clutches throughout the

month, she could make a total of 23 eggs which is a further increase of 15% over the 2-egg

clutch. In order for the hen to be able to produce 300 or more eggs annually, the clutch length

must be 5 or more eggs. Imai (2003) estimated that hens laying at 60% for nine months will

produce as many eggs as a hen laying at 90% for six months.

2.4.7 Rate/Intensity of Lay

The number of eggs produced in a given period of time is dependent on sequence

length. If a hen lays more egg in a given time, then, her rate of lay is high. If the hen lays

more number of eggs per clutch, the hen is usually a better layer than the hen that lays fewer

number of eggs. Although rate of lay is a lowly heritable trait, family selection for this trait

can bring about improvement (Reddy et al., 2004). Butcher and Miles (2000) had observed

that a hen may lay approximately 250 eggs per annum.

Only a few hens lay everyday for 100 or more consecutive days. The rate of lay

depends primarily on the ability of the ovary to produce ova and this has a direct bearing on

30

the stage of life of a hen. Based on individual competence, the laying period of a hen can be

divided into 3 phases

Phase 1: Onset of lay

Phase 2: Main period of lay

Phase 3: Remaining of the pullet year

Phase 1 lasts about one or two months and during which the hens attain their peak

production. The onset of lay corresponds to the seventh month of age and is characterized by

(і) Laying of soft-shelled eggs (іі) Irregular laying with long intervals between eggs and

laying of more than one egg in one day in which one or both may be abnormal. Phase 2 is

characterized by regular egg production and falls within 11 months of age of bird. Phase 3 is a

relatively short period during which egg laying rapidly comes to an end (Latour, 2003; Etches,

1996).

2.5 Egg quality

The quality of an egg is defined by its internal and external attributes. The internal

attributes consist of quality of the albumen and yolk parts, while the external quality is

dependent on the egg shell quality which is related to the existence of cracked shell or stains

(Berardinelli et al., 2005). In general, exterior and internal egg quality standards are based on

shell cleanliness, shell soundness, shell texture, shell shape, relative viscosity of the albumen,

freedom from foreign matter in the albumen, shape and firmness of the yolk, and freedom

from yolk defect (Kemps et al., 2006).

Internal egg quality

Internal egg quality involves functional, aesthetic and microbiological properties of the egg

yolk and albumen. The proportions of components for fresh egg are 32% yolk, 58% albumen

and 10% shell (Robinson and Renema, 1999b).

The egg white is formed by four structures. Firstly, the chalaziferous layer or chalazae,

immediately surround the yolk, accounting for 3% of the white. Next is the inner thin layer,

which surrounds the chalazae and accounts for 17% of the white. Third is the firm or thick

layer, which provides an envelope or jacket that holds the inner thin white and the yolk. It

adheres to the shell membrane at each end of the egg and accounts for 57% of the albumen.

Finally, the outer thin layer lies just inside the shell membranes, except where the thick white

is attached to the shell, and accounts for 23% of the egg white (USDA, 2000).

External egg quality

31

Exterior egg quality is judged on the basis of texture, colour, shape, soundness and

cleanliness according to USDA (2000) standards. It has been always recognized that the hen

has the most extraordinary method of obtaining and depositing calcium (Ca) in the entire

animal kingdom. An egg has an average of 2.3 g of calcium in the shell, and almost 25 mg in

the yolk (Etches, 1996). A modern hen laying 330 eggs per cycle will deposit 767 g of

calcium; assuming a 50% calcium retention rate from the diet, the hen will consume 1.53 kg

of calcium per cycle (Etches, 1996).

2.5.1 Egg weight

This is a highly heritable trait which can be improved by selection. Birds which mature

early tend to lay smaller eggs than those that mature late. The mature egg is approximately 55-

58 gms (Reddy et al., 2004).

Egg weight is influenced by breed, nutrition, season and disease condition. It is also influenced

by the type of housing (Reddy et al., 2004).

2.6 Physical Characteristics

According to Daghir (2008) and Gillespie (1997), in order to determine whether or not

the hen is laying, it is advisable to examine the condition of the comb, wattles, eyes, beaks,

pubic bones, abdomen and vent. A laying hen has large bright, red, soft and waxy comb and

wattles. The eyes are bright and prominent. The beak is bleached. The eyelids and eyerings are

bleached. The pubic bones are flexible and spread wide enough for two to four fingers to be

placed between them. The abdomen is full, soft and pliable. The vent is moist, bleached and

enlarged (Gillespie, 1997). A non-laying hen has a small, pale, scaly and shrunken comb. The

beak is yellow, and the eyes are dull and sunken. The eyelids and eyerings are also yellow. The

pelvis bones are stiff and close together with room for less than two fingers between them. The

abdomen is full and hard. The vent is dry, puckered and yellow (Gillespie, 1997; Obioha,

1992).

Past production is indicated by the amount of yellow pigment left in the body and the

time of moult. Moulting is the process of losing the feathers from the body or wings. Producing

a large number of eggs bleaches the yellow pigment from the hen’s body. The beak, eye ring,

ear lobes and shanks are bleached white. The feathers are worn and soiled. The pigment

bleaches from the hen’s body in a definite order as laying progresses. The pigment leaves the

vent first. It becomes fully bleached after about one week of laying. The eye ring is next to

bleach, requiring about seven to ten days to become fully bleached. The beak bleaches next,

32

starting at the base and progressing to the tip. This takes 4 to 6 weeks. The shanks are last to

bleach. The shank bleaches in this order (1) front of shanks (2) rear of shanks (3) tops of toes

(4) hock joints. It requires 4 to 6 months for the shanks to be fully bleached (Gillespie, 1997).

When the hen stops laying, the pigments return to the body parts in the same order in which it

left. Return of the colour takes about one half of the time required for bleaching. A hen that has

been a poor layer will show yellow pigment in the body parts mentioned above.

A high rate of lay is indicated by the shape and refinement of the head, the width and

depth of the body, the abdominal capacity, the softness and pliability of the skin, the shape of

the shanks. A hen with a high rate of lay has a moderately deep and broad head (Daghir, 2008;

Gillespie, 1997). The face is free of wrinkles and the comb and wattle are fine and smooth

textured. The hen has large body capacity; the abdomen is soft and pliable. The shanks are flat

or wedge shaped.

A hen with poor rate of lay has a long shallow head and a back that is narrow and

tapering. The pubic bones are narrow and thick while the abdomen is hard. The skin is tight

and thick. The shanks are narrow and round.

Obioha (1992) divided layers into good and poor layers as follows:

Good layers Poor layers

Appearance of:

Comb: Large, full, plump, smooth and waxy

Limp covered with white scales, dry,

shriveled

Eye: bright

Dull

Beak: white and well bleached

Yellow colour at base of beak and extending

towards the tip

Eye ring and Earlobe: white and well bleached

Yellow or tinted

Vent: white or well bleached, large, soft,

moist, oval, sometimes over-hanging

Yellow or tinted, small, hard, dry, round

sometimes appear contracted

Wattles: Prominent, soft, smooth

Rough and dry

Face: bright red Yellow tint

33

Head: alert, healthy

Dull, listless

Moulting: sheds feathers late and rapidly

Sheds early and slowly

Pubic bone: thin, pliable, and relatively wide

apart about 2 or more fingers

Thick, blunt and relatively close together, less

than 2 fingers, rigid.

Abdomen: loose, pliable, soft, full when in

laying condition. Deep from pubic bones to

the rear of keel about 4 fingers width

Tight, hard, tucked up. Rear end of the keel

rather close to the pubic bone less than 3

fingers width

Activity: active, alert

Inactive, tired

Plumage: worn, soiled, close New, glossy, loose

2.7 Climatic Condition

For many years, researchers have been investigating the effect of high environmental

temperature and relative humidity on the performance of different poultry species, including

turkeys (McKee and Sams, 1997), young chickens (Henken et al., 1983), broilers (Cooper and

Washburn, 1998), broiler breeders (McDaniel et al., 1995) and laying hens (Emery et al., 1984;

Muiruri and Harrison, 1991; Whitehead et al., 1998), and have found that high environmental

temperatures have deleterious effects on productive performance. In laying hens, heat stress

depresses body weight (Scott and Balnave, 1988), egg production (Muiruri and Harrison, 1991;

Whitehead et al., 1998), egg weight (Balnave and Muheereza, 1997), and shell quality (Emery

et al., 1984; Mahmoud et al., 1996) and is generally accompanied by suppression of feed

intake which could be the cause of decline in production.

Heat stress in poultry is prompted by combinations of environmental temperature and

humidity that prevent the birds’ thermoregulatory processes from effectively dissipating the

heat produced during metabolism. Poultry birds are said to be thermally stressed when ambient

temperature exceeds body temperature such that peripheral physiologic responses of the bird

can no longer match the external changes (Ezekwe, 2011).

34

During heat stress, the environmental parameters of ambient temperature (AT) and

relative humidity (RH) in general and temperature humidity index (THI) in particular, have

been reported to be an invaluable tool in the presumptive diagnosis of the animal state of

health, and is also relevant in evaluating the adaptability of the animal (Tao and Xin, 2003;

Karaman et al., 2007). Altan et al. (2003) reported that high ambient temperature and relative

humidity, increases heat stress and are responsible for the increase in rectal/body temperature.

Chronic heat stress results in behavioural changes, depressed feed intake (Daghir, 2008; Oguz

et al., 2010) and a wide range of metabolic activities (Sahin et al., 2002), including elevation

of body temperature, electrolyte, acid-base and hormonal imbalances (Holik, 2009); and tissue

damage (Sinkalu et al., 2008). Egg production and shell quality in laying hens will be

depressed (Asli et al., 2007; Ajakaiye et al., 2011).

The ideal temperature (conventionally referred to as the zone of thermoneutrality) under

which performance of laying hens is not adversely affected by temperature has been identified

by Holik (2009) and Imik et al. (2009) as 18-220C.

Temperatures outside the critical limits of the thermoneutral zone such as those prevailing

in most humid tropical regions of the world have been reported to constitute heat stress (CTA,

1987; Ensminger et al., 1990; Kucuk, 2003; Hoilk, 2009; Tuleun et al., 2010; Whitehead and

Mitchell, 2010).

Egg quality and production as a whole is affected by temperature which is manifested by

the effect it has on the physiology and metabolism of the hen. During hot weather, there is a

reduction of carbonate ions in the blood which lowers the buffering capacity and may lead to

poor buffering of hydrogen ions produced during shell formation. This explains why there is a

low egg production in hot weather and also why eggs laid during hot weather have thin shells

(Ajakaiye et al., 2011; Asli, 2007). It was also noted by Kirunda et al. (2001) that the specific

gravity of eggs declined at the onset of warm weather.

High temperature could prevent the reproductive tract of laying hens from probably getting

enough nutrient supply as a result of low blood supply and therefore reducing nutrients

reaching the tract for normal egg formation (Ezekwe, 2011).

Excessively high relative humidity makes adaptation to extremes of temperature more

difficult. An increase in relative humidity decrease loss of heat by evaporation at high

temperatures and decreases thermal isolation of the animal at low temperatures (Leeson, 1986).

35

CHAPTER THREE

MATERIALS AND METHODS

3.1 Location and Duration of Study

The study was carried out in the Poultry Unit of the Department of Animal Science

Teaching and Research Farm, University of Nigeria, Nsukka. It lasted for a period of ten weeks

(1st July – 9

th September, 2011).

During this period, hens were observed daily and egg collection was done hourly

between 0600h and 1800h for the first eight weeks, while the subsequent two weeks were used

to appraise their physical characteristics. The study was conducted in late rainy season.

3.2 Experimental Birds

One hundred and fifty 36 weeks old hens, comprising seventy-five Shaver brown and

seventy-five Nera black hens each in their 12th

week of lay were used. The hens were selected

from a flock of laying hens in the farm. Each hen was housed in individual battery cage as

observations were made on individuals.

3.3 Management of Hens

The hens were housed in an open-sided building with a block wall of 90cm high and

wire netting to the roof. Feeding containers used were v-shaped, long and detachable feeders

and water containers used were U – shaped. Hens were fed commercial layers mash containing

16.5% crude protein, 2650 kcal/kg of metabolizable energy, 4% crude fat, 6.5% crude fibre,

3.6% calcium and 0.4% phosphorus. Each hen received about 125g of layers’ mash daily and

ad libitum supply of water . The water supplied to the birds was medicated with an anti-stress

(Vitalyte) for a period of one week at the start of the experiment. Eggs were collected daily and

recorded for each hen.

As a general flock prophylactic management strategy, routine vaccinations and other

health operations were carried out as at when due. Wood shavings were spread under the

battery cages to absorb moisture and ease regular removal of poultry droppings from the laying

house, usually weekly. The surroundings of the experimental birds were kept as tidy as

possible.

36

Dead birds were promptly removed and taken to the Faculty of Veterinary Medicine

University of Nigeria, Nsukka for autopsy when the need arose. No supplemental light was

provided during the period of the study.

3.4 Parameters Measured

3.4.1 Oviposition Time

Oviposition time was recorded hourly during the period of the study.

3.4.2 Total Egg Production

Total egg production was determined by adding all the eggs produced by each of the

two strains of hen during the study.

3.4.3. Clutch/Sequence Length

This was determined for each hen by counting the number of eggs laid until a day was

skipped.

3.4.4 Pause Days

Days in which no egg was laid by the hens were obtained by adding together such

number of days.

3.4.5 Egg Weight (g)

Egg weight was taken for every egg collected for the hens in relation to oviposition

time weighing was done for all eggs within one hour of collection. Electronic balance (D & G

sensitive scale) was used and the measurement expressed in grammes.

3.4.6 Egg Quality

Sixteen (16) eggs per strain were selected at random weekly for egg quality

determination. The indices evaluated were as follows:

i. Egg Shell Weight (g)

Eggs were carefully broken and dried after which the egg shells were weighed

singly using a weighing balance.

ii. Egg Shell Thickness (mm)

This was determined by pulling off the shell immediately the egg was broken and the

shell was air-dried for a day (24 hours) after which the egg shell thickness was determined

with the help of a micrometer screw guage.

37

iv. Egg Shape Index

The egg shape index was calculated as the proportion of egg length to diameter

v. Albumin Height and Diameter (mm/cm)

The eggs after weighing were broken into a piece of flat glass positioned on a flat

surface. The albumin height was measured using a tripod micrometer. Albumin

diameter was taken as the maximum cross sectional diameter of the albumin using a

pair of calipers and read on a ruler calibrated in millimeter.

vi. Yolk Height and Diameter (mm/cm)

The eggs after weighing were broken into a piece of flat glass positioned on a flat

surface. The Yolk height was measured using a tripod micrometer. Yolk diameter

was taken as the maximum cross sectional diameter of the yolk using a pair of

calipers and read on a ruler calibrated in millimeter.

vii. Albumin Index

The albumin index was calculated as the proportion of yolk height to diameter.

viii. Yolk Index

The yolk index was calculated as the proportion of yolk height to diameter.

ix. Haugh Unit

This was calculated from the values obtained from the albumin height and egg

weight by using the formula:

Haugh’s unit = 100log (H+7.57-1.7W0.37

)

3.4.7 Average Daily Feed Intake

Average Daily feed Intake (g): Feed Offered (g) – Feed not eaten (g)

Number of Hens

3.4.8 Percentage Egg Production

Percentage egg production for each strain of hen was calculated using the formula as

shown below:

1

100

75

8%

daysofNoxhousedbreedeachforhensofNo

weeksforbreedeachbylaideggsofNoproductionegg

Other egg production indices were obtained using the formulae as shown below:

38

a. Hen housed egg production (HHEP): It was obtained by dividing the total number of

eggs by each strain of hen by the number of hens housed in the laying cages. This does not

take mortality into account.

Hen housed egg production (HHEP) =

housedhensofNo

laideggsofNo

b. Hen day egg production (HDEP): It was obtained by dividing the total number of eggs by

each strain of hen by the number of hen days.

Hen day egg production (HDEP) =dayshenofNo

laideggsofNo


By visual observation, the conditions of the head, comb, wattles, eyes, beaks, pubic

bones, shanks, abdomen, plumage and vent were appraised and noted for all the hens.

Palpation of palpable physical structures of each hen was made. The hens were divided into

three classes according to their egg production rate and physical characteristics as follows:

good layers, intermediate layers and poor layers.

3.6 Temperature

Temperature readings were taken 3-hourly at time intervals of 0900h, 1200h, 1500h

and 1800h using a standard air thermometer and the mean daily temperatures noted

3.7 Experimental design

The experiment had a completely randomized design with the following model;

Yijk = μ + ai + bj + Ɛijk

Where

Yijk = Observed value of dependent variable

μ = Overall mean

ai = Effect of laying and physical characteristics of the ith individual of Shaver brown hens

bj = Effect of laying and physical characteristics of the jth individual of Nera black hens

Ɛijk = Random error associated with observation

39

3.8 Statistical Analysis

Descriptive statistics such as means and standard error of the means, percentages for

the different parameters were calculated. Data were subjected to analysis of variance

(ANOVA) in a completely randomized design (CRD) using SPSS Package (2003) windows

version 8.0. Significantly different means where separated using Duncan’s New Multiple

Range Test (Duncan, 1955). The statistical procedures used were as described by Steel et al.

(1997).

40

CHAPTER FOUR

RESULTS

The climatic data (Table 2 and Figure 1) taken during the period of the experiment showed that

the study area had the natural day-length of 13 to 14 hours; mean maximum weekly indoor and

outdoor temperatures of 27.90C to 29.2

0C and 26.8

0C to 30.5

0C, respectively; mean minimum

weekly indoor and outdoor temperatures of 20.50C to 22.3

0C and 20.0

0C to 23.60

0C,

respectively; relative humidity of 73.1% to 76.6% and mean total monthly rainfall of

781.33mm.

41

Table 2: Mean weekly environmental temperatures and relative humidity

recorded during the period of study

TEMPERATURES (0C)

WEEK INDOOR OUTDOOR RELATIVE

HUMIDITY

MINIMUM MAXIMUM MINIMUM MAXIMUM

1 20.50 28.90 23.60 27.90 73.1

2 22.30 29.20 23.10 30.50 73.9

3 20.60 29.20 22.80 28.90 73.6

4 21.10 28.50 21.80 29.60 74.7 5 21.20 28.80 22.50 30.00 74.0

6 21.60 28.80 22.60 29.70 75.3

7 20.80 28.70 21.80 29.50 75.8 8 21.00 28.00 21.70 29.50 76.1

9 21.20 28.60 20.00 27.10 73.1 10 21.10 27.90 20.30 26.80 76.6

Thermo neutral zone for poultry is 18-220C (Imik et al., 2009).

42

Figure 1: Average weekly temperatures (indoor and outdoor) and relative humidity of

the study area

10

12

14

16

18

20

22

24

26

28

1 2 3 4 5 6 7 8 9 10

Weeks

Tem

pera

ture

o

C

oC

10

20

30

40

50

60

70

80

Rela

tive h

um

idity

hum

idity

IT Indoor Outdoor

RH

43

4.1 Results

4.1.1 Egg Laying Characteristics of Shaver Brown Hens

4.1.1.1 Oviposition time

As shown in Table 3, more eggs (86.24%) were laid in the morning hours (0600h –

1159h), while 13.76% of egg were laid in the afternoon hours (1200h – 1700h). Oviposition

reached peak between 0630h to 0730h and declined in the early afternoon hours between

1130h – 1230h until eight eggs were laid between 1530h – 1630h (late afternoon hours).

44

Table 3: Frequency distribution of egg laying of Shaver brown and Nera

black hens during the day

Oviposition Interval Strain Number of eggs laid 6:00am-6:59am Shaver brown 467 7:00am-7:59 am

Nera black Shaver brown

520 496

8.00am-8:59 am


555 410

9:00am-9:59 am

Nera black

Shaver brown

497

408

10:00am-10:59 am


493 356

11:00am-11:59 am


333 269

12:00pm-12:59pm


150 174

1:00pm-1:59pm


145 105

2:00pm-2:59pm


108 69

3:00pm-3-59pm


46 33

4:00pm-4:59pm


18 3

5:00pm-6:00pm

Nera black

Shaver brown Nera black

6

0 0

45

Table 4: Frequency distribution of egg production of Shaver brown hens Hen code

No.

Number

observed

Relative

freq.(%)

Hen code

No.

Number

observed

Relative

freq.(%)

Hen code

No.

Number

observed

Relative

freq.(%)

1 46 1.65 27 49 1.76 53 48 1.72

2 44 1.58 28 55 1.97 54 21 0.75

3 41 1.47 29 51 1.83 55 21 0.75

4 38 1.36 30 32 1.15 56 7 0.25

5 38 1.36 31 46 1.65 57 42 1.50

6 45 1.61 32 48 1.72 58 37 1.33

7 43 1.54 33 41 1.47 59 1 0.04

8 39 1.40 34 51 1.83 60 42 1.50

9 29 1.04 35 53 1.90 61 24 0.86

10 46 1.65 36 7 0.25 62 33 1.18 11 44 1.58 37 49 1.76 63 2 0.07

12 48 1.72 38 33 1.18 64 41 1.47

13 43 1.54 39 36 1.29 65 34 1.22

14 51 1.83 40 19 0.68 66 50 1.79

15 44 1.53 41 50 1.79 67 40 1.43

16 29 1.04 42 11 0.39 68 43 1.54

17 47 1.69 43 29 1.04 69 51 1.83

18 37 1.33 44 40 1.43 70 25 0.90

19 36 1.29 45 48 1.72 71 27 0.97

20 28 1.00 46 47 1.69 72 20 0.71

21 33 1.18 47 47 1.69 73 26 0.93 22 31 1.11 48 46 1.65 74 37 1.33

23 43 1.54 49 28 1.00 75 37 1.33

24 44 1.58 50 48 1.72 2790

25 36 1.29 51 45 1.61

26 37 1.33 52 32 1.15

46

4.1.1.2 Total egg production

The distribution pattern of egg production is shown in Table 4.

Result shows that a total of 2790 eggs were laid by Shaver Brown hens during the

experimental period. The average number of eggs produced by a hen was 37.20 . Egg

production by individual hen ranged from 1 - 55. Therefore, the least number of eggs

produced by a single hen within the experimental period was 1 and the highest number of

eggs produced were 55 eggs.

4.1.1.3 Clutch Length

The distribution pattern of the mean clutch length is shown in Table 5. During the

experimental period, clutch lengths of 1 to 17 were observed. Clutch length of 10 occurred

most frequently and clutch length of 1 occurred only once throughout the period. The data

obtained on clutch length shows that about 56% of the clutch lengths were of 10 cycle lengths

and below. The effect of egg position and clutch size on egg weight is shown in Table 6. The

first eggs in a clutch for Shaver brown hens in general were heavier (P<0.05) than eggs

produced later in a clutch. Egg weight across various clutch sizes varied significantly (P<0.05)

for Shaver Brown hens from 2-egg clutch to the 17-egg clutch. 17-egg clutch had the highest

(P<0.05) egg weight of 66.01g, while 10-egg clutch had the (P<0.05) least egg weight of

56.45g.

47

Table 5: Frequency distribution of mean clutch length of Shaver brown hens Hen code

No.

Clutch

length

Relative

freq.(%)

Hen code

No.

Clutch

length

Relative

freq.(%)

Hen code

No.

Clutch

length

Relative

freq.(%)

1 4.60 1.39 27 6.13 1.85 53 9.60 2.90

2 4.00 1.21 28 2.75 8.31 54 4.20 1.27

3 3.73 1.13 29 10.20 3.08 55 1.31 0.40

4 7.60 2.30 30 2.46 0.74 56 1.40 0.42

5 2.71 0.82 31 5.75 1.74 57 3.23 0.98

6 4.50 1.36 32 6.86 2.08 58 2.47 0.75

7 3.58 1.08 33 2.93 0.89 59 1.00 0.30

8 3.25 0.98 34 8.50 2.57 60 4.67 1.41 9 2.07 0.63 35 4.30 1.30 61 1.85 0.56

10 6.57 1.98 36 1.00 0.30 62 3.00 0.91

11 4.89 1.48 37 7.00 2.11 63 1.00 0.30

12 4.00 1.21 38 2.54 0.77 64 2.56 0.77

13 3.91 1.18 39 3.28 0.99 65 2.42 0.73

14 8.50 2.58 40 2.71 0.82 66 7.14 2.16

15 4.40 1.33 41 8.30 2.51 67 3.33 1.01

16 1.81 0.55 42 2.20 0.66 68 3.58 1.08

17 5.22 1.58 43 2.90 0.88 69 8.50 2.57

18 2.64 0.78 44 5.00 1.51 70 2.08 0.63

19 2.57 0.78 45 5.30 1.60 71 3.38 1.02 20 2.80 0.85 46 7.83 2.37 72 1.82 0.55

21 4.13 1.25 47 4.27 1.29 73 1.73 0.53

22 2.58 0.78 48 7.67 2.32 74 3.70 1.12

23 3.07 0.93 49 1.65 0.50 75 4.11 1.24

24 4.00 1.21 50 5.33 1.61 331.09

25 2.00 0.60 51 5.63 1.70

26 2.64 0.78 52 4.00 1.21

48

Table 6: Effect of egg position and clutch size on egg weight of Shaver brown hens

Effect of egg position

on egg weight

Egg weight and its

relationship to clutch

size

Position of eggs Egg weight (g) Clutch size Egg weight (g)

1 64.04a - -

2 63.33ab

2-egg clutch 63.88bc

3 62.87ab

3-egg clutch 65.13ab

4 62.08ab


5 61.56ab

5-egg clutch 59.85de

6 61.91ab

6-egg clutch 60.90de

7 61.63ab

7-egg clutch 61.47cd

8 61.04ab

8-egg clutch 66.85a

9 59.73ab

9-egg clutch 58.60ef

10 59.46ab

10-egg clutch 56.45fg

11 60.70ab


12 60.01ab

12-egg clutch 61.33cd

13 60.45ab


14 58.42ab

14-egg clutch 56.02g

15 60.49ab


16 60.72ab


17 62.44ab

17-egg clutch 66.01ab

SEM 0.23 0.67

a,b,c,d,e,f,g: Mean values in a column with different superscripts are significantly different

(P<0.05)

SEM: standard error of means

49

Table 7: Frequency distribution of pause days of Shaver Brown hens

Hen code

No.

Pause days Relative

freq.(%)

Hen code

No.

Pause days Relative

freq.(%)

Hen code

No.

Pause days Relative

freq.(%)

1 10 0.71 27 7 0.50 53 8 0.57 2 12 0.85 28 1 0.07 54 35 2.48 3 15 1.06 29 5 0.35 55 35 2.48 4 18 1.28 30 24 1.70 56 49 3.48

5 18 1.28 31 10 0.71 57 14 0.99 6 11 0.78 32 8 0.57 58 19 1.35 7 13 0.92 33 15 1.06 59 55 3.90 8 17 1.21 34 5 0.35 60 14 0.99 9 27 1.92 35 3 0.21 61 32 2.27 10 10 0.71 36 49 3.48 62 23 1.63 11 12 0.85 37 7 0.50 63 54 3.83 12 8 0.57 38 23 1.63 64 15 1.06

13 13 0.92 39 20 1.42 65 22 1.56 14 5 0.35 40 37 2.62 66 6 0.43 15 12 0.85 41 6 0.43 67 16 1.14 16 27 1.92 42 45 3.19 68 13 0.92 17 9 0.64 43 27 1.92 69 5 0.35 18 19 1.35 44 16 1.14 70 31 2.20 19 20 1.42 45 8 0.57 71 29 2.06 20 28 1.99 46 9 0.64 72 36 2.55

21 23 1.63 47 9 0.64 73 30 2.13 22 25 1.77 48 10 0.71 74 19 1.35 23 13 0.92 49 28 1.99 75 19 1.35 24 12 0.85 50 8 0.57 1410 25 20 1.42 51 11 0.78 26 19 1.35 52 24 1.70

50

51

Table 8: Effect of oviposition interval on egg weight of Shaver brown hens

Oviposition time interval Egg weight (g) Sig.

6.00am-6.59am 70.05±1.07a *

7.00am-7.59am 68.79±1.52a *

8.00am-8.59am 68.81±0.63a *

9.00am-9.59am 67.85±0.68ab *

10.00am-10.59am 66.07±0.48bc *

11.00am-11.59am 65.63±0.58bc *

12.00pm-12.59pm 63.72±0.49c *

1.00pm-1.59pm 58.22±1.29d *

2.00pm-2.59pm 53.61±0.63e *

3.00pm-6.00pm 51.50±0.43e *

Overall mean 63.43±0.75

a,b,c,d,e: Mean values in a column with different superscripts are significantly different (p<0.05); *=(p<0.05)

52

4.1.1.4 Pause Days

The distribution pattern of the number of pause days is shown in Table 6. The total number of

pause days for all birds were 1410 days. Of these, pause days of 8 and 19 occurred most

frequently and pause days of 1, 14 and 22 were the least.

4.1.1.5 Egg Weight

The mean egg weight for Shaver Brown hens (Table 7) was 63.43 ±0.75(P<0.05) and ranged

from 43 – 89g. Eggs laid in the morning hours were significantly (P<0.05) heavier than those

laid later in the day. The difference in mean egg weight (P<0.05) between eggs laid from

0600h to 0700h and those laid from 1500h to 1800h was 18.55g. The first eggs in a clutch in

general were heavier than eggs produced later in a clutch.

4.1.1.6 Intensity/ Rate of lay

As shown in Table 4, the 56 days used to appraise the laying characteristics of Shaver Brown

hens, the 75 hens laid 2790 eggs, giving overall production rate of 66.43%. Good layers laid

1915 eggs representing 56% of eggs laid, intermediate layers laid 847 eggs accounting for

37.3% and poor layers laid 28 eggs or 6.67% of the eggs laid.

53

4.1.1.7 Hen housed egg production (HHEP):

The mean number of eggs produced by each hen for the period of the study was 45.60 eggs for

good layers; 30.25 eggs for intermediate layers and 5.60 eggs for poor layers (Table 3) . For

the 75 Shaver brown hens altogether, the mean number of eggs produced by each hen was

37.20 eggs during the 56 days of the study.

4.1.1.8 Hen day egg production (HDEP):

The mean number of eggs laid daily by good layers was 34.19 eggs, intermediate and poor

layers 15.12 and 0.5 eggs respectively (Table 3) . The general mean was 49.82 eggs daily.

54

Table 9: classification of experimental hens Strain No. of hens PCLAL No. of eggs Clutch

length

Pause days Physical characteristics

Shaver brown 42

Good

(56%)

45.60

(38-56)

1.32

(1.00-2.20)

11.57

(5-18)

White shanks, bleached

beak, white cloaca.

Nera black 50

Good

(66.67%)

46.02

(38-56)

1.45

(0.0-2.50)

8.58

(2-17)

Shaver brown 28

Intermediate

(37.33%)

30.25

(19-37)

2.67

(1.31-4.30)

25.75

(19-37)

Bleaching shank,

bleaching beak,

bleaching cloaca Nera black 16

Intermediate

(21.33%)

31.88

(19-37)

3.45

(1.71-8.50)

24.13

(19-35)

Shaver brown 5

Poor

(6.67%)

5.60

(0-18)

5.94

(2.71-13.00)

51.20

(49-55)

Dry cloaca

Nera black

9

Poor

(12.00%)

7.08

(8.50-18.0)

55.56

(40-56)

PCLAL = Performance class of layers and % Lay

55

4.1.2 Egg Laying Characteristics of Nera Black Hens

4.1.2.1 Oviposition time

As shown in Table 3 and Figure 1, more eggs (88.75%) were laid in the morning hours (0600h

– 1159h) while 11.25% of eggs were laid in the afternoon hours (1200h – 1700h). Oviposition

reached peak between 0630h to 0730h and declined in the early afternoon hours between

1230h to 1330h until ten eggs were laid between 1530h to 1630h (late afternoon hours).

56

57

Table 10: Frequency distribution of egg production of Nera black hens Hen code

No.

Number

observed

Relative

freq.(%)

Hen code

No.

Number

observed

Relative

freq.(%)

Hen code No. Number

observed

Relative

freq.(%)

1 36 1.25 27 49 1.71 53 54 1.88 2 45 1.57 28 39 1.36 54 39 1.71

3 42 1.46 29 46 1.60 55 50 1.74 4 46 1.60 30 47 1.64 56 42 1.46 5 35 1.22 31 27 0.94 57 44 1.53 6 44 1.53 32 41 1.43 58 50 1.74 7 48 1.67 33 37 1.29 59 46 1.60 8 46 1.60 34 35 1.22 60 44 1.53 9 4 0.14 35 39 1.36 61 21 0.73 10 36 1.25 36 48 1.67 62 13 0.45

11 52 1.81 37 51 1.78 63 48 1.67 12 49 1.71 38 52 1.81 64 51 1.78 13 35 1.22 39 42 1.46 65 21 0.73 14 49 1.71 40 30 1.04 66 49 1.71 15 54 1.88 41 0 0 67 35 1.22 16 47 1.64 42 1 0.04 68 11 0.38 17 1 0.04 43 43 1.50 69 24 0.86 18 28 0.98 44 37 1.29 70 43 1.50 19 51 1.78 45 5 0.17 71 36 1.25

20 51 1.78 46 48 1.67 72 40 1.39 21 48 1.67 47 47 1.64 73 52 1.81 22 49 1.71 48 44 1.53 74 41 1.43 23 16 0.56 49 48 1.67 75 4 0.14 24 48 1.67 50 37 1.29 2871 25 5 0.17 51 47 1.64 26 49 1.71 52 49 1.71

58

4.1.2.2 Total egg Production

The distribution pattern of egg production is shown in Table 10.

Result shows that a total of 2871 eggs were laid by the Nera black hens during the

experimental period. The average number of eggs produced by the hens was 38.28. Egg

production by individual hen ranged from 1 - 54. Therefore, the least number of eggs produced

by a single hen within the experimental period was 1 and the highest number of eggs produced

were 54 eggs.

4.1.2.3 Clutch Length

The distribution pattern of the clutch length is shown in Table 11. During the experimental

period, clutch lengths of 1 to 17 were observed. Clutch length of 10 occurred most frequently

and clutch lengths of 15, 16 and 17 occurred only once each throughout the period. The data

obtained on clutch length show that about 81% of the clutch lengths were of 10 cycle lengths

and below. The effect of egg position on egg weight and clutch size is shown in (Table

12).The first eggs in a clutch for Nera black hens in general were heavier (P>0.05) than eggs

produced later in a clutch.

Egg weight across various clutch sizes varied significantly (P<0.05) for Nera Black hens.

Clutch size ranged from 2-egg clutch to the 17-egg clutch. A clutch of two had the highest

(P<0.05) egg weight of 68.31g, while 6-egg clutch had the least egg weight of 54.44g

(P<0.05).

59

Table 11: Frequency distribution of mean clutch length of Nera Black hens Hen code

No.

Clutch

length

Relative

freq.(%)

Hen code

No.

Clutch

length

Relative

freq.(%)

Hen code

No.

Clutch

length

Relative

freq.(%)

1 7.20 1.71 27 9.80 2.32 53 18.00 4.27 2 4.50 1.07 28 3.90 0.92 54 5.44 1.29

3 3.23 0.77 29 4.60 1.09 55 8.33 1.97 4 4.18 0.99 30 11.75 2.78 56 10.50 2.49 5 3.50 0.83 31 1.93 0.46 57 4.40 1.04 6 4.89 1.16 32 5.13 1.22 58 12.50 2.96 7 5.33 1.26 33 2.18 0.52 59 7.67 1.82 8 4.18 0.99 34 3.50 0.83 60 6.29 1.49 9 1.00 0.24 35 3.00 0.71 61 1.91 0.45 10 5.14 1.22 36 6.86 1.62 62 1.30 0.31

11 13.00 3.08 37 10.20 2.42 63 6.86 1.63 12 6.13 1.45 38 13.00 3.08 64 8.50 2.01 13 2.50 0.59 39 3.20 0.76 65 1.75 0.41 14 8.17 1.94 40 6.00 1.42 66 7.00 1.66 15 18.00 4.26 41 0.0 0.0 67 2.19 0.52 16 4.70 1.11 42 1.00 0.27 68 1.22 0.29 17 1.00 0.24 43 3.91 0.93 69 1.71 0.41 18 5.60 1.33 44 3.08 0.73 70 5.38 1.27 19 8.50 2.01 45 2.50 0.59 71 3.27 0.77

20 7.29 1.73 46 6.86 1.63 72 3.64 0.86 21 5.33 1.26 47 9.40 2.23 73 10.40 0.03 22 8.17 1.95 48 3.67 0.87 74 2.73 0.65 23 1.78 0.42 49 6.86 1.63 75 2.00 0.47 24 6.00 1.42 50 3.70 0.88 422.26 25 1.25 0.30 51 4.70 1.11 26 8.17 1.94 52 9.80 2.32

60

Table 12: effect of egg position and clutch size on egg weight of Nera black hens Effect of egg position

egg weight

Egg weight and its

relationship to clutch

size

Position of eggs Egg weight (g) Clutch size Egg weight (g)

1 63.61 - -

2 62.91 2-egg clutch 68.31a

3 61.39 3-egg clutch 68.19ab

4 60.38 4-egg clutch 61.49de

5 60.07 5-egg clutch 57.21

ef

6 60.50 6-egg clutch 54.44g

7 61.44 7-egg clutch 66.22bc

8 60.54 8-egg clutch 57.03

ef

9 60.97 9-egg clutch 64.91cd

10 60.57 10-egg clutch 61.96de

11 61.56 11-egg clutch 55.04

ef

12 61.82 12-egg clutch 63.65cd

13 61.57 13-egg clutch 63.19cd

14 61.45 14-egg clutch 65.17bc

15 60.12 15-egg clutch 57.60

ef

16 63.28 16-egg clutch 64.71cd

17 63.63 17-egg clutch 65.43bc

SEM 0.21 0.21

a,b,c,d,e,f,g: Mean values in a column with different superscripts are significantly different

(P<0.05)

SEM: standard error of means

61

4.1.2.4 Pause Days

The distribution pattern of the number of pause days is shown in Table 13. The total number of

pause days for all the birds were 1329 days. Of these pause days, of 7 and 8 occurred most

frequently while pause days of 11, 16, 26, 32, 40, 43, 45 and 52 were the least.

62

Table 13: Frequency distribution of pause days of Nera black hens Hen code

No.

Pause days Relative

freq.(%)

Hen code

No.

Pause days Relative

freq.(%)

Hen code

No.

Pause days Relative

freq.(%)

1 20 1.51 27 7 0.53 53 2 0.15

2 11 0.83 28 17 1.28 54 7 0.58 3 14 1.05 29 10 0.75 55 6 0.45 4 10 0.75 30 9 0.68 56 14 1.05 5 21 1.58 31 29 2.18 57 12 0.90 6 12 0.90 32 15 1.13 58 6 0.45 7 8 0.60 33 19 1.43 59 10 0.75 8 10 0.75 34 21 1.58 60 12 0.90 9 52 3.91 35 17 1.28 61 35 2.63

10 20 1.51 36 8 0.60 62 43 3.24 11 4 0.30 37 5 0.38 63 8 0.60 12 7 0.53 38 4 0.30 64 5 0.38 13 21 1.58 39 14 1.05 65 35 2.63 14 7 0.53 40 26 1.96 66 7 0.53 15 2 0.15 41 56 4.21 67 21 1.58 16 9 0.68 42 55 4.14 68 45 3.39 17 55 4.14 43 13 0.98 69 32 2.41 18 28 2.11 44 19 1.43 70 13 0.98

19 5 0.38 45 51 3.84 71 20 1.51 20 5 0.38 46 8 0.60 72 16 1.20 21 8 0.60 47 9 0.68 73 4 0.30 22 7 0.53 48 12 0.90 74 15 1.13 23 40 3.01 49 8 0.60 75 52 3.91 24 8 0.60 50 19 1.43 1329 25 51 3.84 51 9 0.68 26 7 0.53 52 7 0.53

63

4.1.2.5 Egg Weight

The mean egg weight for Nera black hens was 63.08 ±0.71 (P<0.05) and ranged from 44 –

91g (Table 14). Eggs laid in the morning hours were significantly (P<0.05) heavier than those

laid later in the day. The difference in mean egg weight (P<0.05) between eggs laid from

0600h to 0700h and those laid from 1500h to 1800h was 17.44g

64

Table 14: Effect of oviposition interval on egg weight of Nera black hens

Oviposition time interval Egg weight (g) Sig.

6.00am-6.59am 70.10±0.92a *

7.00am-7.59am 69.46±0.71ab *

8.00am-8.59am 68.51±0.72ab *

9.00am-9.59am 67.94±0.64bc *

10.00am-10.59am 66.21±0.55c *

11.00am-11.59am 63.79±0.64d *

12.00pm-12.59pm 59.79±0.51e *

1.00pm-1.59pm 57.39±0.47f *

2.00pm-2.59pm 54.97±0.58g *

3.00pm-6.00pm 52.66±0.71h *

Overall mean 63.08±0.71

a,b,c,d,e, f, g,h: Mean values in a column with different superscripts are significantly different (p<0.05); *=(p<0.05)

65

4.1.2.6 Intensity/ Rate of lay

In the 56 days used to appraise the laying characteristics of Nera Black hens, the 75 hens laid

2871 eggs, giving overall production rate of 68.36% (Table 10). Good layers laid 2301 eggs

representing 80.15% of eggs laid, intermediate layers laid 510 eggs accounting for 17.76% and

poor layers laid 60 eggs or 2.09% of the eggs laid.

66

4.1.2.7 Hen housed egg production (HHEP):

The mean number of eggs produced by each hen for the period of the study was 46.02 eggs

for good layers, 31.88 eggs for intermediate layers and 6.67 eggs for poor layers (Tables 9 and

10). For the 75 Nera black hens altogether, the mean number of eggs produced by each hen

was 38.28 eggs during the 56 days of the study.

4.1.2.8 Hen day egg production (HDEP):

The mean number of eggs laid daily by good layers was 41.09 eggs, intermediate and poor

layers 9.12 and 1.07, eggs respectively (Tables 9 and 10). The general mean was 51.27 eggs

daily.

67

Table 15: Comparison between strains for performance and egg quality traits Parameter

Strain Mean±SE P value Sig.

Hen day egg production Shaver brown 49.82±0.85 0.025 *

Nera black 50.29±0.68

Average daily feed

intake (g)

Shaver brown 59.94±0.40 0.00 *


Egg weight (g) Shaver brown 64.46±0.30 1.58 NS


Egg shell weight (g) Shaver brown 8.06±0.01 0.00 *


Egg shell thickness

(mm)

Shaver brown 0.23±0.02 0.001 *


Egg shape index Shaver brown 1.41±0.003 0.00 *


Albumin height (mm) Shaver brown 7.15±0.32 0.00 *


Albumin index Shaver brown 0.11±0.0004 0.007 * Nera black 0.11±0.0005

Yolk height (mm) Shaver brown 18.62±0.02 0.00 *


Yolk index Shaver brown 0.62±0.01 0.00 *


Haugh unit Shaver brown 83.08±0.18 0.001 *


*= (p<0.05); NS= Not Significant

68

69

Table 16: Effect of temperature on performance of Shaver brown hens PARAMETERS 1

24.500C 2 24.700C

3 24.900C

4 25.000C

5 25.200C

6 25.700C

Overall mean±SE

Sig.

Hen day egg production

56.43±1.63a 50.57±1.53ab 48.71±2.44b 47.71±1.54b 47.43±1.69b 46.57±2.06b 49.82±0.85 *

Average daily feed intake (g)

62.85±0.70a 60.99±0.50ab 58.98±0.68b 60.89±0.77ab 58.75±0.96b 55.13±0.68c 59.94±0.40 *

Egg weight (g)

66.16±1.83 64.40±0.65 64.73±0.64 63.07±0.80 62.98±1.86 64.26±1.56 64.30±0.46 NS

Egg shell weight (g)

8.10±0.01a 8.07±0.004ab 8.06±0.01ab 8.03±0.01b 8.05±0.01ab 8.07±0.05ab 8.06±0.01 *

Egg shell thickness (mm)

0.24±0.004 0.23±0.004 0.24±0.01 0.24±0.02 0.22±0.01 0.24±0.07 0.23±0.03 NS

Egg shape index

1.45±0.01ab 1.46±0.01a 1.45±0.01ab 1.43±0.11bc 1.42±0.01c 1.43±0.01bc 1.44±0.003 *

Albumin height (mm)

7.71±0.06a 7.28±0.04b 7.09±0.06bc 6.99±0.10cd 6.85±0.07de 6.75±0.12e 7.16±0.05 *

Albumin index

0.11±0.00 0.11±0.001 0.11±0.00 0.11±0.00 0.11±0.00 0.11±0.002 0.11±0.001 NS

yolk height (mm)

18.91±0.01a 18.68±0.04b 18.68±0.03b 18.60±0.01b 18.33±0.05c 18.41±0.03c 18.62±0.03 *

Yolk index

0.60±0.001c 0.61±0.002c 0.62±0.004ab 0.63±0.003a 0.62±0.003b 0.62±0.001b 0.61±0.002 *

Haugh unit

86.46±0.15a 83.75±0.24b 82.72±0.05b 82.55±0.10b 81.18±0.11c 81.17±0.37c 83.17±0.24 *

a,b,c,d,e: Mean values in a row with different superscripts are significantly different (p<0.05)

*= (p<0.05); NS= Not Significant

70

Table 17: Effect of temperature on performance of Nera black hens PARAMETERS 1

24.500C 2 24.700C

3 24.900C

4 25.000C

5 25.200C

6 25.700C

7 27.400C

Overal Mean±SE

Sig.


56.71±2.18a 52.36±1.01bc 50.00±1.56bc 48.86±1.10c 48.29±1.32c 47.86±1.50c 54.00±1.22ab 51.30±0.63 *


91.25±1.13a 82.90±1.75b 78.71±1.75bc 78.42±1.14bc 76.25±1.31c 70.70±1.03d 82.59±1.02b 80.47±0.94 *

Egg weight (g)

65.36±1.22a 63.64±0.61ab 63.78±2.15ab 60.90±1.92b 64.07±0.75ab 62.78±1.16ab 66.22±1.77a 63.80±0.52 *


8.09±0.001a 8.02±0.02ab 7.97±0.03b 7.96±0.02b 7.79±0.02c 7.73±0.03d 8.02±o.01ab 7.95±0.02 *

Egg shell thickness (mm)

0.23±0.004a 0.22±0.005abc 0.21±0.004bc 0.21±0.004abc 0.21±0.003bc 0.20±0.003c 0.22±0.01ab 0.21±0.002 *

Egg shape index

1.46±0.002a 1.46±0.001a 1.45±0.002b 1.45±0.002b 1.44±0.002c 1.42±0.002d 1.46±0.00a 1.46±0.002 *

Albumin height (mm)

8.30±0.004a 8.15±0.03b 8.02±0.01c 8.02±0.01c 7.77±0.01d 7.75±0.07d 8.15±0.006b 8.04±0.03 *

Albumin index

0.11±0.00b 0.11±0.00c 0.11±0.00c 0.11±0.00c 0.12±0.00a 0.12±0.00a 0.11±0.00c 0.11±0.004 *

yolk height (mm)

18.51±0.01a 18.46±0.01b 18.31±0.01d 18.31±0.01d 18.30±0.01d 18.25±0.01e 18.41±0.01c 18.38±0.01 *

Yolk index

0.60±0.002bc 0.60±0.001d 0.61±0.002ab 0.61±0.00a 0.61±0.001ab 0.61±0.00a 0.60±0.02d 0.61±0.002 *

Haugh unit

89.03±1.80a 88.38±0.21ab 87.21±0.34cd 87.62±0.39abc 88.68±0.49d 86.19±0.61e 88.04±0.22bc 87.69±0.16 *

a,b,c,d,e: Mean values in a row with different superscripts are significantly different (p<0.05). *= (p<0.05); NS= Not Significant

71

4.1.3 Effect of temperature on performance of Shaver brown and Nera black hens

The effect of temperature on performance of Shaver brown and Nera black hens are shown in

Tables 16 and 17.

Average daily feed intake (ADFI)

The Average daily feed intake (ADFI) was reduced (P<0.05) in proportion to the severity of

heat stress exposure for Shaver brown and Nera black hens. For Shaver brown hens, ADFI

decreased significantly (P<0.05) from 62.85g ±1.83 to 55.13g ±0.68 as the temperature

increased from 24.500C to 25.70

0C. For Nera black hens, ADFI decreased significantly

(P<0.05) as temperature increased from 24.500C to 27.40

0C. Their ADFI ranged from 70.70g

±1.03 to 91.25g ±1.13.

Hen day egg production (HDEP)

The Hen day egg production (HDEP) was inversely related to high temperature. As the

temperature increased from 24.500C to 25.70

0C for Shaver brown hens, HDEP significantly

decreased (P<0.05). Similarly, HDEP significantly decreased (P<0.05) with increasing

temperatures, although this was not the case at 27.400C.

Egg weight

Exposure of Shaver brown hens to high temperatures resulted in a decrease in egg weight

(P>0.05), although the differences were not significant (P>0.05). Mean egg weights ranged

from 62.98g ±1.86 to 66.16g ±1.83 within temperature range of 24.500C to 25.70

0C. For Nera

black hens (Table 21) , temperatures significantly (P<0.05) affected egg weight. Mean egg

weights ranged from 60.90g ±1.92 to 66.22g ±1.77.

Egg shell thickness

Although Egg shell thickness was not significantly decreased (P>0.05) by temperature for

Shaver brown hens, egg shell thickness for Nera black hens decreased significantly (P<0.05)

with increasing temperatures.

Haugh unit

Haugh unit of Shaver brown hens significantly decreased (P<0.05) from 86.46g ±0.15 to

81.17g ±0.37 as the temperature increased. They had significantly higher (P<0.05) Haugh units

at 24.500C while it was lowest at 25.70

0C. Nera black hens had significantly (P<0.05) higher

Haugh units at low temperatures than at high temperatures. Haugh units of 89.03g ±1.80 was

observed at 24.500C, while Haugh units of 88.04g ±0.22 was observed at 27.40

0C.

72

Table 18: Interaction of strain and temperature on performance 24.700C 24.900C 25.000C 25.700C P

value

Sig.

Parameter Strain


Shaver Brown

50.57±1.13 48.71±1.96 47.71±1.96 46.56±1.96 1.00 NS

Nera Black

52.36±1.39 50.00±1.96 48.86±1.96 47.86±1.96


Shaver Brown

60.99±0.77a 58.98±1.34a 60.89±1.34a 55.13±1.34b 0.03 *

Nera Black

82.91±0.95a 78.71±1.34b 78.42±1.34b 70.70±1.34c

Egg weight (g)

Shaver Brown

64.40±0.80 64.73±1.38 63.07±1.38 64.26±1.38 0.94 NS

Nera Black

63.64±0.98 63.78±1.38 60.90±1.38 62.78±1.38


Shaver Brown

8.07±0.13 8.06±0.02 8.03±0.02 8.07±0.02 0.00 NS

Nera Black

8.02±0.16a 7.97±0.02ab 7.96±0.02ab 7.73±0.02b

Egg shell thickness (g)

Shaver Brown

0.23±0.01 0.24±0.01 0.24±0.01 0.24±0.01 0.35 NS

Nera

Black

0.22±0.01 0.21±0.01 0.21±0.01 0.20±0.01

Egg shape index

Shaver Brown

1.46±0.004 1.45±0.01 1.43±0.01 1.43±0.01 0.04 NS

Nera Black

1.46±0.01a 1.45±0.01ab 1.45±0.01ab 1.42±0.01b

Albumin height (mm)

Shaver Brown

7.28±0.04 7.09±0.07 6.99±0.07 6.75±0.07 0.42 NS

Nera Black

8.15±0.05 8.02±0.07 8.02±0.07 7.75±0.07

Albumin index

Shaver Brown

0.11±0.001 0.11±0.001 0.11±0.001 0.11±0.001 0.00 NS

Nera Black

0.11±0.001a 0.11±0.001a 0.11±0.001a 0.11±0.001b

Yolk height

(mm)

Shaver

Brown

18.68±0.02a 18.68±0.04a 18.60±0.04a 18.41±0.04b 0.03 *

Nera Black

18.46±0.03a 18.31±0.04b 18.31±0.04b 18.25±0.04b

Yolk index

Shaver Brown

0.61±0.001b 0.62±0.002ab 0.63±0.002a 0.62±0.002ab 0.00 NS

Nera Black

0.61±0.002 0.61±0.002 0.61±0.002 0.62±0.002

Haugh unit

Shaver Brown

83.75±0.20 82.72±0.34 82.55±0.34 81.17±0.34 0.76 NS

Nera Black

88.38±0.24 87.21±0.34 87.62±0.34 86.19±0.34

a,b: Mean values in a row with different superscripts are significantly different (p<0.05). NS= Not

significant

73

4.1.4 Interaction of strain and temperature on performance

As shown in Table 18, significant interaction (P<0.05) between strain and temperature on

average daily feed intake (ADFI) was observed. ADFI decreased significantly (P<0.05) as the

temperature increased from 24.700C - 25.70

0C. There was no significant interaction (P>0.05)

between strain and temperature on hen day egg production. As the temperature linearly

increased from 24.700C - 25.70

0C, hen day egg production decreased. There was no significant

interaction (P>0.05) between strain and temperature on egg weight. Mean egg weights

(P>0.05) of 64.40g±0.80, 64.73g±1.38, 67.07g±1.38, and 64.26g±1.38 were obtained under

temperatures of 24.700C, 24.90

0C, 25.00

0C, and 25.70

0C respectively for shaver brown hens,

while mean egg weights (P>0.05) of 63.64g±0.98, 63.78g±1.38, 60.90g±1.38 and 62.78g±1.38

were obtained under the same temperature ranges. No significant interaction (P>0.05) between

strain and temperature on egg shell weight was observed. Mean egg shell weights ranged from

8.03g to 8.07g for Shaver brown hens while Nera black hens had egg shell weights (P>0.05)

that ranged from 7.73g to 8.02g. However, Nera black hens had a significant (P<0.05) strain

effect on egg shell weight, which was significantly (P<0.05) lower than that of the Shaver

brown hens. No significant interaction (P>0.05) was observed between strain and temperature

on egg shell thickness, egg shape index, albumin index and yolk index, while significant

interaction (P<0.05) was observed between strain and temperature on yolk height.

4.1.5 Physical Characteristics of hens

As shown in Table 9, Good layers had bright eyes and combs, bleached beaks and shanks,

flexible pubic bones, worn feathers, moist and enlarged vent, soft and pliable abdomen, soft

and smooth wattles. Intermediate layers’ heads, combs, eyes, wattles, abdomen and vent were

nearly the same with good layers except that the beaks, eye rings and shanks showed some

degree of bleaching. On the condition of the plumage, feathers were fairly worn. The pubic

bones were fairly flexible. For poor layers, their combs were dry and shriveled, eyes dull and

eye rings tinted, dull heads, dry wattles but the beak and shank did not show yellow

pigmentation. The feathers were new, abdomen fairly soft, vent fairly moist and pubic bones

relatively close together. For Shaver brown hens, good layers were made up of 42 hens;

intermediate layers, 28 hens, and poor layers, 5 hens. For Nera black hens, good layers were

made up of 50 hens, intermediate layers, 16 hens and poor layers, 9 hens.

74

4.1.6 Comparative performance of Shaver brown and Nera black hens.

Table 15 shows the comparative performance of Shaver brown and Nera black hens


Nera black hens had mean hen day egg production of 50.29±0.68 which was significantly

higher (P<0.05) than that (49.82±0.85) of Shaver brown hens.


The average daily feed intake (ADFI) for Nera black hens was 78.73g±1.12 and this was

significantly higher (P<0.05) than the ADFI (59.94g±0.40) of Shaver brown hens.

Egg weight

There was no significant (P>0.05) difference in egg weight between the two strains. Shaver

brown hens had mean egg weight of 64.46g±0.30 while Nera black hens had mean egg weight

of 64.08g±0.48.

Egg shell weight

The egg shell weight (8.06g±0.01) of Shaver brown hens was significantly higher (P<0.05)

than the egg shell weight (7.94g±0.01) of Nera black hens.

Egg shell thickness

Shaver brown hens had significantly higher (P<0.05) egg shell thickness (0.23mm±0.02) than

Nera black hens which had egg shell thickness of 0.21mm±0.02.

Egg shape index (ESI)

Nera black hens had significantly higher (P<0.05) egg shape index of 1.45±0.002 than Shaver

brown hens with egg shape index of 1.41±0.003

Albumin height and albumin index

The albumin height (8.02mm±0.12) of Nera black hens was significantly different (P<0.05)

from that (7.15mm±0.02) of Shaver brown hens. Likewise, the albumin index (0.11±0.0005) of

75

Nera black hens was significantly different (P<0.05) from the albumin index (0.11±0.0004)

of Shaver brown hens

Yolk height and yolk index

Shaver brown hens had yolk height of 18.62mm±0.02 and this was significantly higher

(P<0.05) than the yolk height (18.36mm±0.01) of Nera black hens. Similarly, Shaver brown

hens had yolk index of 0.62±0.01 and this was significantly higher (P<0.05) than that

(0.61±0.005) of Nera black hens.

Haugh unit

Nera black hens had significantly higher (P<0.05) Haugh units of 88.43±0.16 than Shaver

brown which had yolk index of 0.62±0.01.

76

4.2 Discussion

4.2.1 Climatic Data for Nsukka

Climatic data (Figure 1 and Table 2) for Nsukka during the study were similar to the climatic

data given by Egbunike (2002) who reported monthly minimum temperature range from

18.000C to 24.00

0C, maximum temperatures from 32.25

0C to 38.00

0C and relative humidity

from 46.90 to 81.40% in the humid tropics. It is also consistent with the findings of Mardsen

and Morris (1981) and Payne (1990) who noted that in the tropics, egg production can be

efficient at ambient temperatures as high as 320C but not when temperatures rises above 35

0C

for sustained periods. Relative humidity appeared to have no effect on egg laying performance

at ambient temperatures below 270C although it might have affected performance at higher

temperatures. In practice in the tropics, layers would normally be managed at a somewhat

lower average temperature than 320C.

5.2 Egg Laying Characteristics of Shaver brown and Nera black hens

5.2.1 Oviposition time

Although most eggs were laid before late morning hours (Tables 7 and 14), there was great

variation in the oviposition (egg laying) time. This observation is in agreement with the

findings of Rose (1997), Orji and Nwakalor (1984), McNitt (1983), Ani and Nnamani (2011),

Ajaero and Ezekwe (2006). Rose (1997) reported that domestic fowls lay most of their eggs in

the morning hours. McNitt (1983) also noted that 70% of hens lay their eggs within the first

five hours after day light and 90% within seven hours. Orji and Nwakalor (1984) reported that

Hypeco Goldline and Shaver Brown hens laid 76 and 71 percent of their eggs before 12 noon

respectively. This observations are however, at variance with the findings of Nys and Morgan

(1981) who reported that ovipositions were distributed virtually at random throughout the day.

The disparity could be as a result of differences in the photoperiod of the different study

locations. The birds the earlier researchers worked with could have received less natural light

within the range of time given compared with the amount of day light the birds in the present

study were exposed to in South-East Nigeria. Besides, breed of bird, nutrition, age and weight

of bird, level of production, management system and environmental temperature, laying is also

much affected by season, especially day length (Ahmad et al., 1974; Oluyemi and Roberts,

2000). The sharp decline in the number of eggs produced after 4pm could be as a result of the

77

fact that oviposition rarely occurs after 3.00 pm (Ani and Nnamani, 2011; Ajaero and

Ezekwe, 2006). Smith (2001) reported that chickens do not normally lay eggs in the late

afternoon and therefore once the egg laying is delayed beyond mid-day, oviposition is delayed

until the following day. This assertion is in agreement with the low output of eggs observed

during the afternoon hours in the present study.

5.2.2 Total Egg Production and Other Egg Production Indices

From the results, 2,790 eggs were laid by the 75 Shaver Brown hens for the period of 56 days

with a percentage egg production of 66.43%. The high percentage showed that Shaver brown

hens have adapted favourably to the tropical environment, hence their ability to achieve high

level of egg production. The hen- housed egg production showed that the average number of

eggs laid by each hen for the period of experiment was 37.20 eggs. From hen day egg

production, it was noted that 49.82 eggs were laid daily by the 75 Shaver brown hens. For the

75 hens, the mean egg number per hen would be 298.92 eggs per annum. For Nera black hens,

2871 eggs were laid by the 75 Nera black hens for the period of 56 days with a percentage egg

production of 68.38%. The high percentage showed that Nera black hens have adapted

favourably to the tropical environment, hence their ability to achieve high level of production.

The hen housed egg production showed that the average number of eggs laid by each hen for

the period of the experiment was 38.28. From hen day egg production, it was noted that 51.27

eggs were laid by the 75 Nera black hens. For the 75 hens, the mean number of eggs per hen

would be 307.62 egg per annum .This result is consistent with findings of Nwosu and Omeje

(1985) which showed that the exotic hens are capable of laying 240 to 270 eggs per annum

under tropical environment.

5.2.3 Clutch Length

Shaver brown and Nera black hens used for this experiment laid their eggs in

clutches or sequences which varied from 1 to 17. Hens which had longer clutches had on the

whole larger total egg production. This is consistent with the findings of Ani and Nnamani

(2011) who observed that hens with the longest clutches would produce the largest number of

eggs each laying year because they have the fewest number of non-productive days. The

differences recorded in the clutches of the experimental hens might be due to varying rates of

follicular maturation. Robinson and Renema (1999b) reported that hens that have slow rate of

follicular maturation (26-28h or more) lay shorter (2-3 days) sequences or clutches. On the

other hand, hens that lay very long sequences typically have maturation rates of 24h or perhaps

78

less. It could also be due to heredity or environmental condition (Samak, 2001). Similar

reports have been given by Jakowski and Kaufman (2004) and Etches (1996).

5.2.4 Pause days

Good layers had lower number of pause days while poor layers had highest number

of pause days (Tables 6, 9 and 13). This is in agreement with Jakowski and Kaufman (2004)

who reported that a prolific hen lays five or more eggs in a clutch, the clutches being separated

by not more than a day of rest. Data from the study show that pause days of laying hens

occurred more frequently following oviposition in the afternoon than in the morning hours.

This corroborates with Smith (2001) who reported that chickens do not normally lay eggs in

the afternoon and therefore once egg is delayed beyond mid-day, oviposition is delayed until

the next day. It was also observed that when oviposition occurred after 3pm, hens tended to

pause the next day and following the pause, they would then return to early morning

oviposition earlier than their contemporaries which laid the previous day. It does seem that

there is an inverse relationship between oviposition time and clutch length. Thus, oviposition

interval was found to decrease as clutch length increased and vice versa. Similarly, oviposition

lag decreased as clutch length increased and the lag became negative with long sequence.

5.2.5 Egg Weight

The mean egg weights (P<0.05) of 63.43g ±0.75 and 63.08g±0.71 for Shaver brown

and Nera black hens (Tables 7 and 14), respectively are in conformity with the findings of Orji

and Nwakalor (1984) who reported mean egg weights of 62.83g and 68.81g for Hypeco

Goldline and Shaver Black hens, respectively at Nsukka. It is however, at variance with the

findings of Reddy et al. (2004) and Omeje (1983). Reddy et al. (2004) noted that mature egg

weight generally varied from 55-58gms while Omeje (1983) reported mean egg weight of

59.4g for Goldlink hens at Nsukka. The variation in egg weight might be due to breed or strain

(Nwosu, et al. 1987); position of eggs in a clutch and oviposition time (Ajaero and Ezekwe,

2006); nutrition and ambient temperature (Abutu and Ugwu, 2005); age (Bennett, 2004);

drugs, water quality, intestinal pH (Poultry Hub, 2010).

The heaviest eggs were produced early in the morning and the egg weights

decreased (P<0.05) with the length of clutch (Tables 5 and 12). This report is consistent with

the findings of Novo et al. (1997) and Robinson et al. (1991) that in a clutch, weights of early

laid eggs were greater than those of subsequent eggs in the same clutch. Etches (1996) also

79

noted that because yolk size affects egg size, first eggs in a sequence are invariably heavier

than subsequent eggs of a sequence.

Robinson and Renema (1999a) noted that ovulation follows oviposition by a period

of about 15-45 minutes. When a hen lays an egg late in the afternoon, many hours after the first

egg of a clutch was laid, the hen does not ovulate soon after oviposition because it is too late as

she has exceeded the time limit of her open period of luteinizing hormone (LH). She will

therefore not lay an egg the next day (pause day). The hen will hold the mature F1 follicles

overnight and ovulate it at the start of the next open period for LH release. This means that the

hen will lay early in the day and a new clutch will begin. This probably explains why hens that

have long clutches do so well as they do not take many pause days.

The mean egg weight difference (P<0.05) of 11.10g and 11.47g (Tables 7 and 14)

for Shaver brown and Nera black hens respectively, between the morning eggs and afternoon

eggs conforms to the findings of Zakaria et al. (2005) that egg weight of early laid eggs were

significantly greater than late laid eggs.

5.3 Effect of temperature on performance of Shaver brown and Nera black hens


As shown in Tables 16 and 17, the significant decrease (P<0.05) in average daily feed intake

(ADFI) with increasing temperatures for Shaver brown and Nera black hens is consistent with

the findings of and Muiruri and Harrison (1991), McKee, et al. (1997), Scott and Balnave

(1998), Kirunda et al. (2001) and Mashaly et al. (2004) which showed reduced feed intake

under varying degrees of heat exposure. Similar results have been reported by Picard (1985)

and Emery et al. (1984) who stated that the primary effect of high temperature stress on laying

performance was exerted through reduced feed consumption. The decrease in ADFI could be

due to reduced apetite associated with reduced performance at high temperatures. This result

however, is at variance with the findings of Koelkebeck et al. (1998) who indicated that acute

heat stress had no effect on feed intake in laying hens. The reason could be due to magnitude

of exposure to heat stress.


The significant decrease (P<0.05) in hen day egg production (Tables 16 and 17) corroborates

the findings of Muiruri and Harrison (1991) and Whitehead et al. (1998) that hen day egg

production in white leghorn hens decreased when they were exposed to high environmental

80

temperature. The decrease in egg production could be due to decrease in feed consumption

with the resultant reduction in the available nutrients for egg production.

Egg weight

For Shaver brown hens, increasing temperatures had no significant effect (P>0.05) on egg

weight (Table 16). Similar observations were made by Muiruri and Harrison (1991),

Wolfenson et al. (1979) who reported that heat stress did not significantly affect egg weights.

This may be due to the type of strains used and prevailing environmental temperature.

Egg weights of Nera black hens (Table 17) were significantly (P<0.05) decreased with

increasing temperatures. This is in line with the findings of De Andrade et al. (1976,1977),

Emery et al. (1984), Balnave and Muheerza (1997), Kirunda et al. (2001) and Ahmad and

Roland (2003) that either high temperature or cyclic temperatures decreased egg weight. Their

findings could be due to reduction in feed consumption as reported by De Andrade (1976).

Egg shell weight

As shown in Tables 16 and 17, egg shell weight significantly decreased (P<0.05) with

increasing temperature. This results supports earlier investigations by Emery et al. (1984),

Mahmoud et al. (1996), Asli et al. (2007) and Ajakaiye et al. (2011) which showed decreased

egg shell weight under high temperature. The reason could be due to decreased plasma protein

concentration (Zhou et al., 1998), plasma calcium concentration (Mahmoud et al., 1996), both

of which are required for egg shell formation. In addition, it has been shown that calcium use

(Odom et al., 1986) and calcium uptake by duodenal epithelial cells (Mahmoud et al., 1996)

are decreased by exposure to high environmental temperature. It has also been reported that

plasma calcium level was significantly decreased in laying hens (Mahmoud et al., 1996) and in

turkeys (Kohne and Johnes, 1976) when birds were exposed to high temperatures.

Also, high temperature could prevent the reproductive tract of laying hens from probably

getting enough nutrient supply as a result of low blood supply and therefore reducing nutrients

reaching the reproductive tract for normal egg formation (Ezekwe, 2011). This result however

contrasts the findings of Wolfenson et al. (1979) who noted that heat exposure did no

significantly affect egg shell weight. This could be due to small temperature range the hens

were subjected to during the experiment and perhaps due to the genetic makeup of individual

strains.

81

Egg shell thickness

As shown in Table 16 for Shaver brown hens, increasing temperatures did not significantly

(P>0.05) affect egg shell thickness. This is in line with the findings of Muiruri and Harrison

(1991) that high temperature did not significantly affect shell thickness. This presumably could

be as a result of variation in temperatures of the different study locations. For Nera black hens

(Table 17), there was a significant decrease (P<0.05) in egg shell thickness with increasing

temperatures. This supports the findings of Emery et al. (1984) and Mahmoud et al. (1996)

that there was decrease in egg shell weights of heat stressed birds. This could be as a result of

reduction in feed consumption associated with heat stress as reported by Andrade (1976).

Haugh unit

The Haugh unit (Tables 16 and 17) was significantly (P<0.05) higher for Shaver brown and

Nera black hens under low temperatures but significantly decreased (P<0.05) with increasing

temperatures. This supports the findings of Kirunda et al. (2001) that Haugh units of eggs from

heat stressed birds were reduced after heat exposure. This disagrees with the findings of

Mashaly et al. (2004) who reported significantly higher Haugh units in eggs of birds exposed

to high temperatures. This could be as a result of varying degrees of heat exposure in the

different study locations.

5.4 Interaction of strain and temperature on performance


As shown in Table 18, the significant interaction (P<0.05) between strain and temperature on

ADFI is consistent with the findings of Mashaly et al. (2004), Kirunda et al. (2001), Scott and

Balnave (1998), McKee et al. (1997) and Muiruri and Harrison (1991) which showed reduced

feed intake under varying degrees of heat exposure. Similar results have been reported by

Picard (1985) and Emery et al. (1984) who stated that the primary effect of high temperature

stress on laying performance is exerted through reduced feed consumption. The decrease in

ADFI could be as a result of reduced appetite associated high temperatures. This result

however, is at variance with the findings of Koelkebeck et al. (1998) that acute heat stress had

no effect on feed intake in laying hens. This could be due to differences in environmental

temperature and strain of birds used.

82


As shown in Table 18, there were no significant interaction (P>0.05) between strain and

temperature on hen day egg production. This corroborates investigations carried out by

Mardsen et al. (1987) and Emery et al. (1984). Mardsen et al. (1987) reported increased egg

production rate by 1.1% on pullets exposed to temperatures of 180C-24

0C. This could be due to

small variation in temperature range (24.700C-25.70

0C) and different strains of birds used.

These findings, however contrasts the reports of Whitehead et al. (1998), Muiruri and Harrison

(1991) that hen day egg production in white leghorn hens decreased when they were exposed

to high environmental temperature. Perhaps, it could be that the environmental temperatures

the hens were subjected to in the present study were not high enough to have led to decrease in

HDEP.

Egg weight

Table 18 shows that there were no significant interactions (P>0.05) between strain and

temperature on egg weight. Similar observations were made by Muiruri and Harrison (1991)

and Wolfenson et al. (1979) who stated that heat stress did not significantly affect egg

weights. This may be due to the type of strains used, cyclic temperatures and age of the hen.

This is however inconsistent with the findings of Emery et al. (1984), De Andrade et al.

(1976,1977), Balnave and Muheerza (1997), Kirunda et al. (2001) and Ahmad and Roland

(2003) that either high temperature or cyclic temperatures decrease egg weight. Their findings

could be due to reduction in feed consumption as reported by (De Andrade, 1976).

Egg shell weight

As shown in Table 18, no significant interactions (P>0.05) between strain and temperature on

egg shell weight were observed. This supports the findings of Wolfenson et al. (1979) who

noted that heat exposure did not significantly affect egg shell weight. This could be that the

temperature the hens were subjected to during the experiment was not too high as to have

affected egg shell weigh. However, Nera black hens had a significant (P<0.05) strain effect on

egg shell weight which was lower than that Shaver brown hens. This result supports earlier

reports by Emery et al. (1984), Mahmoud et al. (1996), Asli et al. (2007) and Ajakaiye et al.

(2011) which showed decreased egg shell weight under high temperature. The reason could be

83

due to decreased plasma protein concentration (Zhou et al., 1998) and plasma calcium

concentration (Mahmoud et al., 1996), both of which are required for egg shell formation. It

has also been shown that calcium use and calcium uptake by duodenal epithelial cells are

decreased by exposure to high environmental temperature (Odom et al. 1986; Mahmoud et al.

1996). It has also been reported that plasma calcium level was significantly decreased in laying

hens (Mahmoud et al. 1996) and in turkeys (Kohne and Johnes, 1976) when birds were

exposed to high temperatures. Also, high temperature could prevent the reproductive tract of

laying hens from probably getting enough nutrient supply as a result of low blood supply and

therefore reducing nutrients reaching the reproductive tract for normal egg formation (Ezekwe,

2011).

Egg shell thickness

It was observed (Table 18) that there were no significant interaction (P>0.05) between strain

and temperature on egg shell thickness. This is in line with the findings of Muiruri and

Harrison (1991) that high temperature did not affect egg shell thickness. This presumably

could be because of strain differences. This however, contrasts the findings of Emery et al.

(1984) and Mahmoud et al. (1996). This could be due to differences in degree of exposure to

heat stress or strain of birds used. Similar observation was made by Andrade (1976)

Haugh Unit

As shown in Table 18, there were no significant interactions (P>0.05) between strain and

temperature on Haugh unit. This supports the findings of Kirunda et al. (2001) who reported

that Haugh units of eggs from heat stressed birds were reduced after heat exposure. This

disagrees with the findings of Mashaly et al. (2004) who reported significantly higher Haugh

units from eggs of birds in hot chamber. This could be as a result of variation in temperatures

of the different study locations.


Results from the physical characteristics agreed with the reports of Obioha (1992), Gillespie

(1997), Daghir (2008), Ani and Nnamani (2011) and Ajaero and Ezekwe (2006) that laying

hens had large, bright red, soft and waxy combs and wattles; bright and prominent eyes;

84

bleached beaks, eyelids and eyerings; flexible rigid bones; soft and pliable abdomen; moist

and enlarged vent.

Based on the number of eggs produced, number of pause days and physical

characteristics, the hens were classified into good layers, intermediate layers and poor layers

(Table 9). For Shaver brown hens, good layers were those that produced 38-56 eggs for 56

days, had mean clutch length of 1.32 and pause days of 5-18. For Nera black hens, good layers

produced 38-56 eggs, had mean clutch length of 1.45 and pause days of 2-17. They also had

the following physical characteristics: full, plump, smooth and waxy comb; prominent, soft

and smooth wattles; bright eyes, bright red face, beak, eyering, earlobe and vent(cloaca), as

well as white or bleached shanks. Their vents were white or well bleached, large, soft, moist,

oval and sometimes overhanging; the pubic bones were thin, pliable and relatively wide apart

to accommodate about two or more fingers within the inter-pubic space as described by

Oluyemi and Roberts (2000), Ajaero and Ezekwe (2006) and Daghir (2008).

Intermediate layers for Shaver brown hens produced 19-37 eggs, mean clutch

length of 2.67 and pause days of 19-37. For Nera black hens, intermediate layers produced 19-

37 eggs, had mean clutch length of 3.45, and pause days of 19-35. Their physical

characteristics such as combs, wattles, eyes and abdomen were same as seen in good layers.

The beak showed some degree of bleaching. The lateral side of the beak was bleached or white

(fully bleached). The caudo-cranial part (base) was bleached or white (fully bleached) while

the tip was white. The shanks showed some degree of bleaching. The region of the meta-tarsal

joint and some parts of the toes were yellow. The dorsal part (back) and lateral part were white.

The frontal aspect-the region above the meta-tarsal joint and the hock joint were white.

Besides, the eyelids, eye ring and earlobe were bleached. They had moist, enlarged, dilated,

bleached and pliable cloaca when compared with poor layers and moist, bleached, pliable,

intermediately enlarged and dilated cloaca when compared with good layers. Their feathers

were worn, soiled and scruffy as in good layers. Moreover, the pubic bones were soft, thin and

relatively wide apart, while the face was bright. Just like good layers, the intermediate layers

were relatively active, alert and well-fed. The observed features were similar to the features

described by Smith (2001) and Ani and Nnamani (2011). For Shaver brown hens, poor

layers were classified based on the fact that for Shaver brown hens they produced 0-18 eggs in

56 days, and they had mean clutch length of 5.94 and pause days of 49-55. For Nera black

hens, poor layers produced 0-18 eggs, had mean clutch length of 7.08 and pause days of 40-

85

56. They had the following physical characteristics: combs were shriveled, dry and covered

with white scales; eyes were dull; wattles were rough and dry; face was yellowish; abdomen

was tight, hard and tucked up with the rear end of keel; the pubic bones were very close and

could not accommodate about two or more fingers within the inter-pubic space as described by

Obioha (1992), Oluyemi and Roberts (2000) and Ani and Nnamani (2011). Unlike in good and

intermediate layers where the abdomen was loose, pliable, soft and full when in laying

condition, the pubic bones were rigid, thick, blunt and relatively close together. Moreover, the

beak was yellow at the base, tip and sides, whereas the vent (cloaca) was yellow or tinted,

small, hard, dry, round and sometimes appeared contracted.

5.6 Comparative performance and egg quality traits of Shaver brown and Nera black

hens


As shown in Table 15, hen day egg production was significantly higher (P<0.05) in Nera black

hens than Shaver brown hens. This result is in close agreement with those obtained by Goher et

al. (1994) and Nofal et al. (2000) who reported that hen day egg production of Mamourah

strains were significantly higher than that of Gimmizah strains. The reason could be as a result

of genetic differences between the strains. The result however disagrees with that reported by

Samak (2001) which showed that hen day egg production was not affected by the differences

in the strains of birds studied.


As shown in Table 15, Shaver brown hens ate less (P<0.05) than Nera black hens, possibly

because of genetic differences, physical activity, physical condition, basal metabolic rate, body

temperature and body composition as reported by Nofal et al.( 2000) and Luiting ( 1990).

Egg weight

As shown in Table 15, strain differences had no significant effect (P>0.05) on egg weight. This

result supports the reports of Goher et al. (1994), Nofal et al. (2000) and Samak (2001) that

egg weight was not affected by strain. This result however disagrees with the findings of

Hanson (1991) and Abd-ElGalil (1993) which showed that significant differences in egg

weight existed between strains.

86

Egg shell weight and Egg shell thickness

As shown in Table 15, egg shell weight and egg shell thickness of Nera black hens were

significantly higher (P<0.05) than those of Shaver brown hens. This could be due to varying

egg shell quality associated with different types of strains of laying hens (Curtis et al., 1985).

Albumin and yolk height

Albumin heights of Nera black hens (Table 15) were significantly higher (P<0.05) than

albumin heights of Shaver brown hens. Similarly, yolk height of Shaver brown hens were

significantly higher (P<0.05) than that of Nera black hens. This could be due to genetic

differences between the two strains (Nofal et al., 2000; Luiting, 1990).

Haugh unit

The Haugh unit of Nera black hens (Table 15) was significantly higher (P<0.05) than that of

Shaver brown hens. This could be as a result of genetic differences between the strains

(Luiting, 1990; Nofal et al., 2000).

87

CHAPTER SIX

SUMMARY AND CONCLUSION

A study was conducted to evaluate the laying and physical characteristics of Shaver brown and

Nera black hens in the humid tropical environment. The results showed that Shaver Brown and

Nera black hens lay more eggs between 0600h and 1100h, but the peak laying period was

0700h to 0800h. Eggs laid in the first oviposition interval of 0600h to 0700h were bigger than

those laid in other oviposition intervals. The mean egg weight of the first eggs laid in a clutch

were the bigger than those of the subsequent eggs laid in a clutch. With egg production rate of

66.43% and 68.36% for Shaver brown and Nera black hens, respectively, the Shaver brown

hens and Nera black hens could lay 223.2 and 229.68 eggs, respectively in a year.

Comparatively, Shaver brown hens had higher egg weight, egg shell weight, egg shell

thickness, yolk height and yolk index than Nera black hens. Similarly, Nera black hens had

higher hen day egg production, average daily feed intake, egg shape index, albumin height, and

Haugh unit. The findings in this study tend to indicate that although heat stress had effect on

performance, Shaver brown and Nera black are good layers and are adapted to humid tropical

environment. This result could be helpful in establishing guidelines for temperature control in

laying houses, especially during hot season when birds are most susceptible to heat stress.

Conclusion

The results obtained in the present study show that although heat stress had effect on

performance, Shaver brown and Nera black hens are good layers and are adapted to humid

tropical environment.

88

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APPENDICES

APPENDIX 1 A) Analysis of variance (ANOVA) Table for egg weight and its relationship to oviposition interval

Duncana EGGWT Shaver Brown

OvipoINT Subset for alpha =0.05

N 1 2 3 4 5

10 9

8 7 6 5 4 2 3 1

Sig.

8 8

8 8 8 8 8 8 8 8

51.5050 53.6113

.87

58.2237

1.000

63.7200 65.6275 66.0713

.070

65.6275 66.0713 67.8475

.087

67.8475 68.7888 68.8050 70.0538

.101

Means for groups in homogenous subsets are displayed. a. Uses Harmonic Sample Size = 8.000

Duncana

EGGWT Nera Black

OvipoINT

N

Subset for alpha = 0.05

1 2 3 4 5 6 7 8

10 9 8 7 6 5 4

3 2 1 Sig.

8 8 8 8 8 8 8

8 8 8

52.6600

1.000

54.9737

1.000

57.3850

1.000

59.7938

1.000

63.7850

1.000

66.2125 67.9413

.067

67.9414

68.5125 69.4638 .126

68.5125 69.4638 70.1000 .110

Means for groups in homogenous subsets are displayed. a. Uses Harmonic Sample Size = 8.000 B) Analysis of variance (ANOVA) Table for egg weight and its relationship to clutch size

98

EGGWT Shaver brown Duncan a,,b

CLUCTH No. Subset for alpha = 0.05

N 1 2 3 4 5 6 7

14 10 9 5 6

12 7 15 4 13 2 11 16

3 17 8 Sig.

42 30 27 40 30

36 21 45 28 39 14 44 32

9 34 24

56.0145 56.4520

.709

56.4520 58.6026

.067

58.6026 59.8537 60.8970

.064

59.8537 60.8970

61.3317 61.4705

.214

61.3317 61.4705 63.4167 63.4721 63.5492 63.8800 63.8827 63.8922

65.1278 66.0106 .063

61.3317 61.4705 63.4167 63.4721 63.5492 63.8800 63.8827 63.8922

65.1278 66.0106 .059

66.8467 .169

Means for groups in homogenous subsets are displayed. a. Uses Harmonic Mean Sample Size = 25.845 b. The group sizes are unequal. The harmonic mean of the group sizes is used. Type 1 error levels are not guaranteed.

EGGWT Nera black Duncan a,,b

CLUCTH No. N Subset for alpha = 0.05

1 2 3 4 5 6 7

6 11 8 5 15 4 10

13 12 16 9 14 17 7 3

2 Sig.

42 33 32 45 45 36 30

39 36 32 27 42 34 28 21

20

54.4424 55.0391

.248

57.0278 57.2058 57.6044

.296

61.4856 61.9560

.362

63.1867 63.6483

.371

64.7053 64.9122 65.1729 65.4338

.202

65.1729 65.4338 66.2200

.055

68.1876

68.3050 .820

Means for groups in homogenous subsets are displayed. a. Uses Harmonic Mean Sample Size = 32.053 b. The group sizes are unequal. The harmonic man of the group sizes is used. Type 1 error levels are not guaranteed. C) Analysis of variance (ANOVA) Table for egg weight and its relationship to position of eggs in a clutch

99

EGGWT Shaver brown Duncan a,,b

POSITION N


1 2

14 10

9 12 13 15 11 16 8 5 7

6 4 17 3 2 1 Sig.

10 23

26 16 13 7 20 4 29 45 32

37 52 2 55 62 62

58.4220 59.4574

59.7265 60.0125 60.4446 60.4857 60.7030 60.7200 61.0397 61.5640 61.6341

61.9143 62.0794 62.4400 62.8738 63.3271 .058

59.4574

59.7265 60.0125 60.4446 60.4857 60.7030 60.7200 61.0397 61.5640 61.6341

61.9143 62.0794 62.4400 62.8738 63.3271 64.0371 .078

Means for groups in homogenous subsets are displayed. a. Uses Harmonic Mean Sample Size = 11.733 b. The group sizes are unequal. The harmonic mean of the group sizes is used. Type 1 error levels are not guaranteed.

EGGWT Nera black Duncan a,,b

POSITION N Subset for alpha = 0.05

1

5 15

4 6 8 10 9 3 7 14

14 11 13 12 2 16 1 17

Sig.

49 7

58 40 29 22 25 65 33 10

19 13 16 75 4 75 2

60.0682 60.1200

60.3788 60.4965 60.5372 60.5736 60.9732 61.3915 61.4382 61.4510

61.5589 61.5708 61.8188 62.9101 63.2775 63.6092 63.6250

.144

Means for groups homogenous in homogenous subsets are displayed. a. Uses Harmonic Mean Sample Size = 11.807 b. The group sizes are unequal. The harmonic mean of the group size is used. Type 1 error levels are not guaranteed.

100

APPENDIX 2 Effect of temperature on performance of Shaver brown hens

a) Analysis of variance(ANOVA) Table for Hen Day Egg Production (HDEP)

HDEP Duncan a,,b

IndoorTEMP N


1 2

25.70 25.20 25.00 24.90 24.70 24.50 Sig.

7 7 7 7 21 7

46.5714 47.4286 47.7143 48.7143 50.5714 .239

50.5714 56.4286 .54

Mean for groups in homogenous subsets are displayed

a) Uses Harmonic Mean Sample Size = 7.875 b) The group sizes are unequal. The harmonic mean of the group sizes is used. Type 1 error levels are not guaranteed.

B) ANOVA Table for Average Daily Feed Intake (ADFI)

DFI Duncan a,,b

IndoorTEMP N Subset for alpha = 0.05

1 2 3

25.70 25.20 24.90 25.00 24.70 24.50 Sig.

7 7 7 7 21 7

55.1286 1.000

58.7500 58.9786 60.8900 60.9867 .061

60.8900 60.9867 62.8457 .090

Means for groups in homogenous subsets are displayed.


C) ANOVA Table for Egg Weight (EGGWT)

EGGWT Duncan a,,b

IndoorTEMP N


1

25.20 25.00

25.70 24.70 24.90 24.50 Sig.

7 7

7 21 7 7

62.9814 63.0686

64.2571 64.4038 64.7271 66.1269 .119

Means for groups in homogenous subsets are displayed. a) Uses Harmonic Mean Sample Size = 7.875 b) The group sizes are unequal. The harmonic mean of the group sizes is used. Type 1 error levels are not guaranteed.

101

D) ANOVA Table for EGG Shell Weight (ESWT)

ESWT Duncan a,,b

IndoorTEMP N Subset for alpha = 0.05

1 2

25.00 25.20 24.90 24.70

25.70 24.50 Sig.

7 7 7 21

7 7

8.0300 8.0486 8.0600 8.0652

8.0729 .165

8.0486 8.0600 8.0652

8.0729 8.0952 .126

Means for groups in homogenous subsets are displayed. a) Uses Harmonic Mean Sample Size = 7.875 b) The group sizes are unequal. The harmonic mean of the group sizes is used. Type 1 error levels are not guaranteed..

E) ANOVA Table for Egg Shell Thickness (EST)

EST Duncan a,,b

IndoorTEMP N


1

25.20 24.70 25.00 24.90 25.70 24.50 Sig.

7 21 7 7 7 7

.2186

.2324

.2357

.2386

.2414

.2429

.086


a) Uses Harmonic Mean Sample Size = 7.875 b) The group sizes are unequal. The harmonic mean of the group sizes is used. Type 1 error levels are not guaranteed..

F) ANOVA Table for Egg Shape Index (ESI)

ESI Duncan a,,b

IndoorTEMP N

Subset for aplpha = 0.05

1 2 3

25.20 25.00 25.70 24.50

24.90 24.70 Sig.

7 7 7 7

7 21

1.4243 1.4286 1.4314 1.4457

.094

1.4286 1.4314 1.4457

1.4507 .083

1.4457

1.4507 1.4571 .354


102

G) ANOVA Table for Albumin Height (ALBHT) Duncan a,,b

ALBHT

IndoorTEMP Subset for alpha = 0.05

N 1 2 3 4 5

25.70 25.20 25.00 24.90

24.70 24.50 Sig.

7 7 7 7

21 7

6.7500 6.8529 6.9886

.346

6.8529 6.9886

.215

7.0871

.366

7.0871

7.2833 .075

7.7143 1.000


H) ANOVA Table for Albumin Index (ALBI) Duncan a,,b

ALBI

IndoorTEMP N


1

24.70 25.70 24.50 24.90 25.00

25.20 Sig.

21 7 7 7 7

7

.1067

.1071

.1100

.1100

.1100

.1100

.102


I) ANOVA Table for Yolk Height (YHT)

Duncan a,,b

YHT

IndoorTEMP N


1 2 3

25.20

25.70 25.00 24.70 24.90 24.50 Sig.

7

7 7 21 7 7

18.3300

18.4143 .182

18.5971 18.6748 18.6800 .216

18.9100 1.000

Means for groups in homogenous subsets are displayed. a) Uses Harmonic Mean Sample Size = 7.875

b) The group sizes are unequal. The harmonic mean of the group sizes is used. Type 1 error levels are not guaranteed.

103

J) ANOVA Table for Yolk Index (YI)

YI Duncan a,,b

IndoorTEMP N


1 2 3

24.50 24.70 25.20 25.70 24.90

25.00 Sig.

7 21 7 7 7

7

.5986

.6057

.073

.6186 .6186 .6229

.307

.6229

.6286

.149


K) ANOVA Table for Haugh Unit (HU)

HU Duncan a,,b

IndoorTEMP N


1 2 3 4

25.70 25.20 25.00 24.90 24.70 24.50 Sig.

7 7 7 7 21 7

81.1714 81.1771 .989

82.5514 82.7200 .675

83.7467 1.000

86.4629 1.000


104

APPENDIX 3 Effect of temperature on performance of Nera Black hens

a) Analysis of variance(ANOVA) Table for Hen Day Egg Production (HDEP)

HDEP Duncan a,,b

IndoorTEMP N


1 2 3

25.70 25.20 25.00

24.90 24.70 27.40 24.50 Sig.

7 7 7

7 14 7 7

47.8571 48.2857 48.8571

50.0000 52.3571 .053

50.0000 52.3571 54.0000 .069

54.0000 56.7143 .189

Means for groups in homogenous subsets are displayed. a) Uses Harmonic Mean Sample Size = 7.538

b) The group sizes are unequal. The harmonic mean of the group sizes is used. Type 1 error levels are not guaranteed.

B) ANOVA Table for Daily Feed Intake (DFI)

DFI Duncan a,,b

IndoorTEMP N


1 2 3 4

25.70 25.20

25.00 24.90 27.40 24.70 24.50 Sig.

7 7

7 7 7 14 7

70.7000

1.000

76.2500

78.4243 78.7071 .315

78.4243 78.7071 82.5900 82.9050 .077

91.2500 1.00



C) ANOVA Table for Egg Weight (EGGWT)

EGGWT Duncan a,,b

IndoorTEMP N


1 2

25.00

25.70 24.70 24.90 25.20 24.50 27.40 Sig.

7

7 14 7 7 7 7

60.8957

62.7786 63.6400 63.7786 64.0714 .150

62.7786 63.6400 63.7786 64.0714 65.3629 66.2200 .125



105

D) ANOVA Table for Egg Shell Weight (ESWT)

ESWT

Duncan a,,b

IndoorTEMP N


1 2 3 4

25.70 25.20 25.00 24.90 24.70 27.40

24.50

7 7 7 7 14 7

7

7.7257

1.000

7.9943

1.000

7.9614 7.9743 8.0200 8.0200

.100

8.0200 8.0200

8.0871 .051


E) ANOVA Table for Egg Shell Thickness (EST)

EST Duncan a,,b


N 1 2 3

25.70 25.20 24.90 25.00 24.70 27.40 24.50

Sig.

7 7 7 7 14 7 7

.2029

.2071

.2100

.2114

.2171

.070

.2071 .2100 .2114 .2171 .2200

1.03

.2114 .2171 .2200 .2257

.063


F) ANOVA Table for Egg Shape Index (ESI)

ESI Duncan a,,b

IndoorTEMP Subset for alpha =

0.05

N 1 2 3 4

25.70

25.20 24.90 25.00 27.40 24.50 24.70 Sig.

7

7 7 7 7 7 14

1.4157

1.000

1.4443 1.000

1.4529 1.4529 1.000

1.4600 1.4629 1.4629 .267



106

H) ANOVA Table for Albumin Height (ALBHT)

ALBHT Duncan a,,b

IndoorTEMP N


1 2 3 4

25.70 25.20 25.00 24.90 27.40

24.70 24.50 Sig.

7 7 7 7 7

14 7

7.7457 7.7743

.301

8.0214 8.0243

.917

8.1486

8.1500 .956

8.3029 1.000


I) ANOVA Table for Albumin Index (ALBI)

ALBI Duncan a,,b


N 1 2 3

24.50 24.90 25.00

27.40 24.70 25.20 25.70 Sig.

7 7 7

7 14 7 7

.1100

.1100

.1100

.1100 1.000

.1100 1.000

.1200 .1200 1.000


J) ANOVA Table for Yolk Height (YHT)

YHT Duncan a,,b


N 1 2 3 4 5

25.70 25.20 24.90 25.00 27.40

24.70 24.50 Sig.

7 7 7 7 7

14 7

18.2529

1.000

18.3029 18.3071 18.3114

.630

18.4129

1.000

18.4593 1.000

18.5129 1.000


107

K) ANOVA Table for Yolk Index (YI)

YI Duncan a,,b

indoorTEMP Subset for alpha = 0.05

N 1 2 3

27.40 24.70 24.50 24.90 25.20

25.00 25.70 Sig.

7 14 7 7 7

7 7

.6029

.6036

.6043

.6057

.244

.6043 .6057 .6086

.070

.6057 .6086

.6100

.6100

.080


L) ANOVA Table for Haugh Unit (HU)

HU

Duncan a,,b

IndoorTEMP N


1 2 3 4 5

25.70 25.20 24.90 25.00 27.40 24.70

24.50 Sig.

7 7 7 7 7 14

7

86.1943 86.6729

.297

86.6729 87.2071 87.6214

.053

87.2071 87.6214 88.0414

.088

87.6214 88.0414 88.3807

.120

88.3807

89.0300 .159


108

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OKPARA, MORGAN OBINNAs Project Corrected... · than subsequent eggs laid in a clutch, while the first eggs in a clutch for Nera black were greater than other eggs in the clutch, although