EFFECT OF ELECTRICAL STUNNING ON

BROILERS CARCASSES QUALITY

BY:

MORTADA MOHAMMED FADLALLA AHMED

B.Sc. (Honours) Animal Production Science

Faculty of Animal Production

University of Khartoum

November 2003

A dissertation submitted to University of Khartoum

in partial fulfillment for the degree of Master of

Science in Poultry Production

Supervisor: Dr. Abbaker Ali Idris

Department of Poultry Production

Faculty of Animal Production

University of Khartoum

2007

CORE Metadata, citation and similar papers at core.ac.uk

Provided by KhartoumSpace

I

DEDICATION

My honest gratitude and regards to my:

Mother.….

Father.…

Brothers….

And Sisters….

For giving me the emotional support, the

patience, and the perseverance needed throughout

my study.

II

ABSTRACT

This study has been carried out to investigate the effect of electrical

stunning on quality of broiler carcasses .The experiment was conducted in

the processing plant of the Arab Poultry Production and Processing

Company (ARAPPCO), south of Khartoum.

The experiment has been done on eighty broilers of the same strain

(Ross308) and age. The birds were divided evenly into four treatment

groups. The treatments include an electrical stunning current of 0mA,

25mA,35 mA and 45mA.

The observed effects of the electrical stunning on the apparent

characteristics of the slaughtered broilers include: red wing tips, red tail, red

feather tract on breast and wings, broken bones, wing veins engorgement,

feather on wings and tail, physical activity after stunning and blood spots on

breast meat, in addition to the determination of the blood loss percentage and

the pH of the hot breast meat.

The results showed that the physical activity of the stunned birds

were significantly (P<0.05) and progressively reduced by the increasing

dose of the stunning current.In terms of carcass quality, the higher doses of

the stunning current although significantly reduced the blood spots of the

breast muscles which subsequently leads to enhancement of carcass quality,

they increased the presence of feathers on wings and tails which are

accounted against the carcass quality, whereas the other characteristics did

not record any significant differences (P>0.05) among them. From the

obtained results the effect of electrical stunning on breast meat pH was

noted, but the blood loss percentage was not affected by the treatments.

III

ملخص الدراسة

فى ذبائح الفراخ جودةأجريت هذه الدراسة لتقصى تأثير إستخدام الصعق الكهربى على ال

جنوب ) ARAPPCO(تم إجراء الدراسة بمجزرشرآة إنتاج وتصنيع الدجاج العربى .اللاحم

.الخرطوم

قسمت إلى ) 308روص ( النوع العمر و نفس عدد ثمانين طائرا منأجريت الدراسه علي

بعة مجموعات تجريبية متساوية العدد وأخضعت آل منها إلى معاملة مختلفة،شملت هذه أر

مللى أمبير ،بينما 45 مللى أمبير ، 35 مللى أمبير، 25المعاملات إستخدام التيار الكهربى بقوة

.موعة الرابعة دونما تعريض للتيارترآت المج

إحمرار : لى الصفات الظاهرية مثل تم ملاحظة الأثر الناتج عن المعاملات المختلفة ع

أطراف الجناح،إحمرار الذيل،إحمرار قواعد الريش فى الصدر والجناح،العظام المكسورة،تضخم

والبقع ،صعقالأوردة تحت الجناح،وجود الريش على الأجنحة والذيل،حرآة الطائر عقب عملية ال

أثر الصعق الكهربى على الأس نسبة فقد الدم،وحساببالإضافة لتقدير.الدموية على لحم الصدر

).بدون تبريد(الهيدروجينى للحم الصدر

حيث تنخفض الصعق فى حرآة الطيور عقب (P<0.05) أظهرت النتائج فروقا معنوية

وبالرغم من أن زيادة التيار تخفض بصورة معنوية من البقع ،تدريجيا بزيادة التيار المستخدم

تحسين جودة الذبائح إلا أن ذلك يؤدي من جهة أخري لزيادة لحم الصدر مما يؤدي لالدموية علي

بينما لم تسجل أى من الصفات . وجود الريش علي الأجنحه والذيل وبالتالي التقليل من جودة الذبائح

من خلال النتائج المتحصلة وضح تأثير الصعق . فيما بينها(P>0.05)الأخرى فروقا معنوية

.نى للحم الصدر،فى حين لم تتأثر نسبة فقد الدم بأى من المعاملاتالكهربى على الأس الهيدروجي

IV

ACKNOWLEDGEMENTS

First of all and foremost, my heartfelt thanks to almighty Allah for

giving me the willpower, strength and patience to achieve this work.

My deepest sincere and gratitude are due to my supervisor

Dr. Abbaker Ali Idris, Department of Poultry Production, Faculty of

Animal Production, University of Khartoum, for his unlimited help, advice,

constructive guidance, patience and encouragement throughout the course of

this work.

My genuine, sincere thanks are owed to Dr.Mohamed Khair

Abdullah for his unlimited assistance in analysis of the data.

My thanks are due to the staff of the Department of Poultry

Production, for their faithful help.

Thanks are extended to Dr.Mohammed Abbas and the staff of the

processing plant of the (ARAPPCO) for their supports.

Also I would like to express my deep thanks to my friends and

colleagues who directly or indirectly helped in this work.

Finally, the efforts of those helped in a way or another are gratefully

acknowledged.

THANKS TO EVERY ONE.

V

LIST OF CONTENTS

No. Title pag

e

Dedication I

Abstract II

Arabic abstract III

Acknowledgements IV Contents V List of tables VII

CHAPTER ONE

General Introduction 1

CHAPTER TWO : LITERATURE REVIEW 2.1 Stunning 4

2.2 Electrical stunning 5

2.3 Principles of electrical stunning 6

2.4 Electrical water bath stunning 7

2.4.1 Stunning and electrical circuit 7

2.4.2 Electrical stunning and slaughter practices 8

2.4.3 Stunning methods 9

2.4.4 Electrical stunning and carcass quality 10

CHAPTER THREE :MATERIALS AND METHODS 3. Materials and methods 18

3.1 Study area 18

3.2 Experimental birds 18

VI

3.3 Slaughtering procedure 18

3.4 Carcass defects 19

3.5 Meat quality 19

3.6 Statistical analysis 19

CHAPTER FOUR Results 21

CHAPTER FIVE Discussion 28

REFERENCES 33

APPENDEX 42

VII

LIST OF TABLES

TABLE TITLE Page

1 Effect of electrical stunning on carcass characteristics 23

2 The effect of electrical stunning on percentage blood

loss for broiler chicken bled for 120 second.

24

3 The effect of electrical stunning on broiler breast muscle

pH.

25

4 The effect of electrical stunning on broiler breast

muscle’s pH at different postmortem times.

26

5 The effect of electrical stunning and time on pH 27

1

CHAPTER ONE

INTRODUCTION

Poultry meat production and consumption were predicted by the

United Nation Food and Agriculture Organization (FAO) to increase by

more than 20% over the next six years with an average annual growth

rate of 2.5%. Most of the increase will occur in developing countries

.This trend will be driven by the low production cost and price of

poultry meat (relative to beef ) , rising income and standards of living ,

and changing consumer preferences on health (low in fat ) or social

( convenient , fast food ) grounds .However , issues concerning the

origin, safety and quality of meat , bird welfare and environmental

impact of poultry production and processing are likely to play important

roles in world trade .Evidently , farm animal welfare , in general , has

become an issue of increasing concern to consumers, producers,

governments and nongovernmental organizations. Stunning methods

used for poultry are electrical and gas stunning. The Stunning/ killing

methods on the other hand include induction of cardiac arrest at

stunning in water bath stunner, exposure to gas mixtures until the birds

are dead, and penetrating or nonpenetrating captive bolts (Mead, 2004).

Electrical stunning of poultry is performed by passing an electric

current either across the head ( head – only stunned ) or through the

whole body using an electrified water bath (water bath stunning )

supplied with high frequency current ( usually above 200 Hz) that do

not induce death via cardiac arrest or ventricular fibrillation at stunning.

The amount of current (mA) applied during electrical stunning must be

sufficient to induce immediate loss of consciousness, typically in less

than one second. Stork meat processing systems, in conjunction with the

2

University of Utrecht in the Netherlands, developed the first automatic

electrical stunning system in 1987.

Water bath stunning is applied to relax neck muscles and contract

wing muscles for easy fixation of the head for automatic killers. It

prevents excessive struggling and wing – flapping during bleed – out,

facilitates rapid bleeding, and relaxes or loosens feathers. This method

of electrical stunning is quick, and the system required for on line

operation is relatively inexpensive. Although there are many makes of

commercially available electrical stunners, for the most part their design

and operation are similar. A fiberglass brine-water bath cabinet is

supported under the overhead conveyor line from which chickens move

supported on shackles. The cabinet is vertically adjustable and usually

set at a height that allows the heads of the birds to be submerged in

brine-bath water. An electrified metal grate is submerged in the bottom

of the brine-water bath tank. Although the shackle line is connected to

earth, a ground bar contacting the shackles is often used to complete the

electrical circuit.

The birds pass through the stunner cabinet in a continuous

procession. When a voltage is applied between submerged electrode and

the earth (ground), the current flows through the immersed chickens in

the cabinet to complete the circuit. Chickens in this type of circuit

represent a series of resistors connected in parallel.

Regardless of differences in cultural, religious, and regulatory

practices governing slaughter of poultry, the application of electrical

stunning principles in slaughter plants and the effect of stunning on end

product quality are of concern to processors worldwide. In the Sudan,

poultry industry has expanded its operations following the very

optimistic forecasts on increasing consumption of poultry products on

3

the next coming years. Therefore, many enterprises have been

constructed concerning on the production and processing of poultry.

Electrical stunning has been used in the Sudan in many

companies that produce the broilers. This system is now practiced in:

Arab Poultry Production and Processing Company (ARAPPCO), Arab

Company for Livestock Development (ACOLID), Hamza Farm,

Sheibaika Farms, and Tayba Company. Despite the trend of this latter

information which indicates the adoptition of the electrical stunning

practice in most of the established broiler- processing plants, no studies

have been conducted to evaluate the impact of the stunning process on

the quality attributes of the final products .Moreover, there is evidence

that some methods of the electrical stunning (those required by

European regulations in particular) have been recorded to induce

increased incidences of carcass damage.

1.1: Objectives:

This study has been planned to highlight the influences of

electrical water bath stunning on physical quality of broiler carcasses. The

main objective of study is to evaluate the effects of the electrical water bath

stunning on carcass quality in form of apparent defects (breast meat blood

spots, wing and tail feathers, broken bones, red wing tips, red tail, red

feather tract on breast and wings and wing veins engorgement).

4

CHAPTER TWO

LITERATURE REVIEW

2.1: Stunning:

Stunning was originally performed as a method of animal

immobilization to allow easier and safer manipulation of large animals for

neck handling and efficient cutting of the blood vessels. In poultry, for which

immobilization during slaughter was not as critical to manual killing,

stunning was necessary for the subsequent development of efficient

automated killing machines. In recent years, stunning has been viewed

primarily from an animal welfare perspective as a mean to minimize the pain

and suffering associated with slaughter. From an animal welfare perspective,

stunning should produce a rapid onset of stress-free insensibility of sufficient

duration to allow the animal to remain unconscious until dead, either from

the results of the stun itself or due to subsequent killing operations such as

neck cutting during slaughter (Fletcher, 1999; Savenije et al., 2002).

Stunning prior to slaughter can be accomplished using chemical,

mechanical, or electrical means. Chemical means include gas stunning with

carbon dioxide, argon, nitrogen, or other agents that ultimately result in

unconsciousness and possibly death via anoxia. Mechanical means include the

archaic method of “brain sticking” (piercing the brain) or concussion, as used

in large animal slaughter. Because of the logistic and welfare difficulties of

positioning the bird for mechanical methods under automated line conditions,

there are at present no commercial systems in use. Electrical stunning is by far

the most widely used method of preslaughter stunning in poultry. (Fletcher,

1999).

Various forms of stunning, ranging from a physical blow to the head

to more recently developed gas immersion systems, have been used in animal

5

slaughter. The primary functions of stunning are to render the animal

unconscious for easier handling during slaughter and to render the animal

insensible to pain. In recent years, there has been considerable public concern

for the welfare of food animals, including poultry species, during stunning and

slaughter. The European Union (1993) adopted detailed rules of welfare-at-

slaughter which are set down in Council Directive 93/119/EC on the

protection of animals at the time of slaughter or killing. Presently, the

technologies to humanely stun and slaughter poultry are widely employed. The

methods legally usable for stunning include captive bolt pistol, concussion,

electronarcosis and exposure to carbon dioxide. From an animal welfare

perspective, stunning should produce a rapid onset of stress-free insensibility

of sufficient duration to allow the bird to remain unconscious until dead, either

as a result of the stun itself or due to subsequent killing operations such as

neck cutting during slaughter (Fletcher, 1999; Savenije et al., 2002).

Preslaughter stunning is conventionally used in the European poultry industry

to achieve the legal requirement of immobilizing and rendering birds

insensible to pain before death by exsanguination (Wask, 1955).

2.2: Electrical stunning:

Electrical stunning systems for poultry were initially developed to

immobilize the bird long enough to allow physical manipulation of the bird for

alignment in automated neck cutting equipment (killer) and to reduce carcass

damage due to unconscious physical activity such as wing flapping and violent

muscular contractions during bleeding. Commercial processing plants

presently slaughter up to 140 to 180 birds a minute. Occasionally, due to a

lack of bird uniformity, or poorly adjusted and maintained equipment, birds

may miss one or both of the automated stunning and killing equipment,

necessitating manual back-up. Consistency in making a proper unilateral neck

cut, one that severs the carotid artery and the jugular vein, it is necessary to

6

allow rapid blood loss sufficient to kill the bird prior to entering the scalder

and requires continual monitoring and equipment adjustment. In the early

1980s, it was observed that as many as 30% of birds slaughtered in Europe

were under stunned (Heath, 1983).

The use of electrical stunning is common in both the red meat and

poultry processing industries. Electrical stunning systems in poultry were

initially developed for the purpose of temporarily immobilizing birds to insure

consistent presentation of the bird to automated neck cutting machines.

Electrical stunning also decreases involuntary bird movement during the death

struggle, decreasing carcass damage (Gregory et al., 1991).

Stunning is not required in the United Kingdom if slaughter is

instantaneous, as with decapitation or dislocation of the neck. Electrical

stunning is the most common method used prior to slaughter in commercial

poultry plants. Although five types of electrical stunning systems are available

(Gregory, 1989), the most common system is electrical water bath stunning

(Bilgili, 1992). Electrical stunning methods used in the past include electrified

knives, electrified contact grids or plates, and a V-shaped stunner. The most

common one is the water bath stunner (Reynolds1943).

2.3: Principles of electrical stunning:

Electrical stunning is accomplished by passing a sufficient amount of

electrical current through the central nervous system of birds for a given

amount of time (Bilgili, 1992).The state of unconsciousness induced by

electricity results from the inhibition of impulses from both the reticular

activating and the somatosensory systems (Heath et al.,1994).Loss of

somatosensory evoked potentials and spontaneous electroencephalograms

have been directly related to brain failure and instantaneous insensibility to

pain (Richard and Sykes, 1967; Lopes da Silva, 1983;Gregory and Wotton,

1989, 1990).The stunning current reaching the brain must be adequate enough

7

to induce an epileptic seizure. This current is usually lower than that required

for ventricular fibrillation and, hence, death by electrocution. Insufficient

currents may physically immobilize the bird, but may not prevent perception

of pain, stress, or discomfort by the animal. Hence, if the bleeding is not rapid,

birds may regain consciousness prior to scalding (Fletcher, 1993).

2.4: Electrical water bath stunning:

Electrical water-bath stunning is the most common method of

immobilizing birds for easier killing in commercial poultry processing plants

(Bilgili, 1992; Raj, 1998; Savenije et al., 2002). Electricity is convenient,

economical, and requires little room. Much diversity exists in electrical

equipment, concepts, and approaches to water-bath stunning. Poultry are

commonly stunned by means of an electrified water bath. Electrical current

runs from the submerged electrode through the head and body of the

chickens, with the shackles or a metal bar against the legs functioning as the

ground electrode (Bilgili, 1992).

2.4.1: Stunning and electrical circuit:

The amount of current that flows through each individual bird is

dependent upon the voltage applied and the electrical impedances of the

birds in the brine water bath. Woolley et al. (1986 a,b) have shown that

whole bird resistance of broilers ranges between 1,000 to 2,600Ω.More

recently, sex differences in resistance were also reported, with females

exhibiting higher resistance than males (Rawles et al.,1995). As the birds

enter and leave the stunner cabinet, they constantly change the total

resistance of the system. At a given constant voltage, the birds receive a

current in proportion to their own resistance. In addition, the resistance

provided by the water or brine solution is also critical and has been shown to

vary under commercial conditions (Bilgili, 1992). By passing sufficient

electric current through the brain, a general epileptiform insult will occur,

8

which is characterized by rapid and excessive depolarization of the

membrane potential (Fricker and Muller, 1981).

Commercial stunners provide a choice of alternating or direct currents,

either low or high frequency, half or full rectified, sine or square waveforms,

constant or pulsed currents (Ingling and Kuenzel, 1978;Griffith and

Purcell,1984;Bilgili.1992;and Heath et al.,1994).The effectiveness of an

electrical stunning system is dependant upon not only the electrical variables

used (i.e., current, voltage, waveform, frequency, and duration), but also the

biological factors that affect the bird impedance (i.e., size, weight, sex,

composition, and feather cover) (Kettlewell and Hallworth, 1990).Woolley

et al. (1986 a,b) has shown that individual birds, as well as different tissues

within a bird, vary in their resistance. Given the typical biological variation

observed among the birds within or between the flocks processed. It is not

surprising that the research and development of stunning technology have

been driven primarily by defining and standardizing the electrical variables

used in stunning.

2.4.2: Electrical stunning and slaughter practices:

In the U.S.A, the blood vessels within the neck of the bird(both carotid

arteries and jugular veins) are severed usually by a deep ventral cut within 8

to 12 s of stunning. This methodology is accomplished by automatic neck

cutters and by back-up personnel (Heath et al., 1994). The ensuing rapid

drainage of blood causes anoxia and often prevents birds from regaining

consciousness during the subsequent 80 to 90 s bleed time. In Europe, the

neck cut is performed dorso-laterally or on one side only. Because the rate of

blood loss is slower, the bleed times are usually extended to 120 to 180 s.

This type of cut often leaves major blood vessels that supply the brain intact,

giving birds the opportunity to regain consciousness when the cut or

bleeding is incomplete (Gregory,1992). This potential for regaining

9

consciousness has been the major reason from the humane standpoint that

current levels of 120 to 150 mA per bird have been suggested in Europe to

ensure an instantaneous and irreversible stun, i.e., “stun-to-kill” (Fletcher,

1993).Contrasting with Europe, the electrical currents used in the U.S.A,

have been traditionally much lower (25 to 45mA per bird).Also, the deep

bilateral neck cuts often severe the trachea and cause the heads to come off

in the pickers. Concern over the removal of a section of trachea that is

usually left attached to the neck has prevented many processors in Europe

from using deep ventral neck cuts in the past (Bilgili, 1999).

2.4.3: Stunning methods:

In U.S.A, poultry are specifically not included in the legislation

covering the humane slaughter of livestock and as such stunning conditions

are not mandated. Differences exist in the methods of stunning between the

U.S. and Europe. Although not specifically required, a survey of poultry

slaughtering plants in the U.S. shows that more than 97% of all poultry are

subjected to electrical stunning (Heath et al., 1994). In this survey, 92% of

the broilers were electrically stunned and the majority of the remaining 8%

were subject to religious slaughter. Of the 329 poultry slaughter plants

surveyed in 1991, 279 (85%) used electrical stunning, 216 (66%) used low

voltage, high frequency (10 to 25 volts, 500 Hz), and the remaining 63 plants

(19%) reported variations in stunning conditions ranging from 7.5 to 600V.

No specified waveform [alternating (AC) or direct current (DC)] whereas

currents ranging from 0.3 to 10 mA. The authors concluded that although

there were variations in methods of stunning and slaughter, the majority of

plants were in voluntary compliance with the humane slaughter provisions,

and the birds were stunned sufficiently to remain unconscious through

exsanguinations.

10

Research conducted primarily in Germany and the United Kingdom

resulted in European recommendations that broilers be stunned with a

minimum of 120 mA to both instantaneously render the animal unconscious

and to affect heart failure such that the animal can not recover consciousness.

Therefore, electrical stunning systems in Europe are generally “high current”

systems designed to irreversibly stun (i.e., “stun to- death”) the bird to insure

animal welfare. Although such high current systems have also been related to

increased incidences of carcass quality defects, the recommendation for a

minimum stunning current was based solely on achieving optimum welfare

and not on avoiding carcass defects (van Hoof, 1992).

Stunning with high electrical currents is a humane method, when

compared to low amperage or no stun, because there is less likelihood of a

bird regaining consciousness before death (Gregory and Wotton, 1986).

However, the high amperage applied in Europe causes more carcass and

meat damage than the lower amperage customarily used in the United States

(Craig and Fletcher, 1995; Hillebrand et al., 1996; Kang and Sams, 1999).

2.4.4: Electrical stunning and carcass quality:

Europe produces over 8.5 million tones of poultry meat per year. With

the conventional method of electrical water bath stunning followed by

cutting the neck veins to slaughter poultry, animal welfare and meat quality

often require contradictory settings of the stunning apparatus. A low

stunning current could lead to chickens suffering during death struggle.

Poultry welfare during slaughter can be guaranteed by applying a stun-kill,

which requires high current levels (Gregory and Wotton, 1987). However,

high current levels result in carcass and meat quality problems, such as

hemorrhages and broken bones (Griffiths, 1985; Hillebrand et al., 1996).

Therefore, the industry is reluctant to use a high stunning current. As yet,

11

there has been no agreement on a minimum current for electrical stunning

within the European Union.

In the U.S.A poultry industry, low current (10 to 45 mA) electrical

stunning is primarily used to reduce pain (Kuenzel and Walther, 1978),

improve killing efficiency during automated killing (Fletcher, 1993; Poole

and Fletcher, 1995), aid in bleed out (Kuenzel et al., 1978), and decrease

feather release force (Dickens and Shackelford, 1988). However, in the

European Community, where the birds’ welfare is a primary concern, high

current (>100 mA) electrical stunning is used to induce irreversible

unconsciousness (Bilgili, 1992; Gregory and Wotton, 1994). Violent

contractions associated with high amperage (>100 mA) electrical stunning,

as conducted in the European Community, result in carcass quality problems

such as hemorrhaging and bone fracturing (Gregory and Wilkins, 1989).

As the poultry industry has become more involved in further

processing, the importance of strict process control to maintain consistent

meat quality is increasing. At the same time, quality characteristics that

affect consumer acceptability are changing. Instead of emphasizing carcass

characteristics, such as absence of defects and skin color, new emphasis is

being placed on functional characteristics of the meat, such as texture,

moisture binding, and color. These latter quality characteristics are directly

affected by ante- and post-mortem glycolytic activity. In general, functional

properties are enhanced when the muscle retains its chemical characteristics,

such as ante-mortem levels of pH and intracellular calcium concentrations

(Froning and Neelakantan, 1971; Young and Lyon, 1997).

Preslaughter electrical stunning, which is routinely used to immobilize

poultry prior to mechanical killing, has been shown to alter both the rate of

post-mortem glycolysis (Lee et al., 1976; Thomson,et al., 1986; Papinaho et

al., 1995; Papinaho and Fletcher, 1996) and the functional characteristics

12

such as texture (Thomson et al., 1986; Young and Lyon, 1997), protein

solubility (Murphy et al., 1988), and color (Papinaho and Fletcher, 1996).

However, most studies have compared results from stunned birds with those

of unstunned birds or stunning at various currents or potentials. Little

information has been published concerning effects of stunning duration on

functional characteristics. Typically, processors in the U.S. stun broilers at

about 50 V (alternating current) for 10 s or less; however, stunning

conditions are usually adjusted to maintain efficient Killing with minimal

carcass damage rather than to maintain optimal functional characteristics.

In the European Community it has been recommended that the

minimum stunning current for broilers should be 120 mA, so as to induce

cardiac arrest in 90% of the birds, such that they will not regain

consciousness during exsanguinations (Gregory, 1992). The reasoning

behind this high current system of “stunning” is to provide for the welfare of

the birds; i.e., it guarantees that birds are not subjected to any conscious

stresses that can be associated with recovery from stunning. In the U.S.

however, the major emphasis of stunning is to render the bird immobile with

the least amount of stunner-related carcass damage. Low voltage/low current

stunners are commonly used in 65% of U.S. processing plants (Heath et al.,

1994).

During conventional water bath stunning, electrical current passes

through the whole body, causing muscle contraction, broken bones, and

breast muscle hemorrhages (Hillebrand et al.,1996). The use of electrical

stunning with higher stunning frequencies, e.g. 1,500 Hz, to prevent chickens

from ventricular fibrillation and downgrading results in fewer broken bones

than stunning with 50 Hz (Gregory et al., 1990).

Electrical stunning has been associated with a decrease in carcass

blood loss (Kotula and Helbacka, 1966; Kuenzel and Ingling, 1977; Schutt-

13

Abraham et al., 1983; Veerkamp and de Vries, 1983; Murphy et al., 1988;

Papinaho and Fletcher, 1995a), although some exceptions have also been

reported (Heath et al., 1983; Griffiths et al., 1985; Dickens and Lyon, 1993).

Recent research suggests that electrical stunning only affects the rate of early

blood loss and has little effect on the ultimate carcass blood loss (Schutt-

Abraham et al., 1983; Gregory and Wilkins, 1989b; Papinaho and Fletcher,

1995b).

Research was undertaken that led to the European Union

recommendations for high-current stunning sufficient to cause instantaneous

and irreversible unconsciousness in order to ensure a humane slaughter (van

Hoof, 1992). These high-current, stun-to-kill methods have been associated

with increased carcass and meat quality defects.

In the process of slaughtering poultry, electrical stunning is used both

to make the slaughter procedure as humane as possible, by rendering the

animals unconscious, and to immobilize them for easier killing. In practice,

however, electrical stunning in high rate slaughter lines does not stun all

chickens adequately (Heath, 1983); thus, chickens may suffer during death

struggle. With regard to the final product, inadequate stunning can lead to an

increased number of red skin carcasses, blood spots in the meat, and color

differences (Griffiths, 1985; Hillebrand et al., 1996). The final result of

inadequate stunning is increased animal suffering and poorer meat quality

(Veerkamp and De Vries, 1983; Gregory and Wotton, 1987a; Gregory and

Wilkins, 1989; Schutt-Abraham, 1995).

By passing sufficient electric current through the brain, a general

epileptiform insult will occur, which is characterized by rapid and excessive

depolarization of the membrane potential (Fricker and Muller, 1981). Upon

electrical stunning, the animal may die due to a heart attack and loss of

oxygen to the brain. Insufficient currents may physically immobilize the bird

14

but may not prevent perception of pain, stress, or discomfort by the animal

(Bilgili, 1999). Electrical stunning causes depolarization of neurons in the

brain, which results in brain function disturbances in the form of a general

epileptiform insult (Fricker and Muller, 1981). Appearance defects result in a

decline in sales and, thus, economic losses to poultry processors (Fricker and

Muller, 1981; Alisch and Obdam, 1992). Evidently, there is some conflict

between animal welfare and meat quality. Therefore, it is essential that

alternative stunning methods be explored.

Electrical stunning with high current frequencies is one of the

alternatives to conventional low frequency (50 Hz) water bath stunning

(Hillebrand et al., 1996). The use of high frequency (ε480 Hz) stunning

currents results in an increased rate of postmortem pH decline and improved

meat quality, compared to the lower frequency (δ350 Hz) waveforms

(Gregory et al., 1991; Wilkins et al., 1998, 1999; Sante et al., 2000). These

results can be accounted for by the fact that higher current frequencies cause

a lower degree of direct stimulation of tonic muscle contraction and, thus,

result in fewer carcass and meat defects (Hillebrand et al., 1996).

Gregory and Wilkins (1989a) found that some defects appeared to be

affected by the level at which the stunning current was applied. The

incidence of shoulder hemorrhages and red wing tips was highest between

111 and 150 mA, and breast muscle hemorrhages increased after 130 mA.

The increasing effect of higher electrical currents on the incidence of broken

bones was observed by Wilkins and Scott (1987) and Gregory and Wilkins

(1989a, 1990).

Gregory et al. (1991) reported that, as stunning amperages were

increased from 60 to 110 mA, incidence of ventricular fibrillation increased

from 20 to 99%. The increased incidence of ventricular fibrillation would

result in birds not recovering consciousness following the electrical stunning

15

process (i.e., the birds would actually die from the electrically induced

fibrillation if not by the subsequent actual neck cutting and bleeding

process).

Although high current stunning systems render the bird unconscious,

they are associated with increased carcass damage and meat defects.

Veerkamp and deVries (1983) found that, as stunning voltages increased, the

incidence of red wing tips and tails increased. Similar results were observed

in a series of studies by Gregory and Wilkins (1989a,b,c), who found that

when ventricular fibrillation was induced in broilers during stunning, the

incidence of red wing tips and hemorrhaging at the humerus-radius joint

increased. The authors reported that breast muscle hemorrhaging in turkeys

and broken bones in broilers increased as stunning amperage was increased.

Walther (1991) reported that stunning-related carcass damage, such as

broken bones, could be reduced if the stunner voltage was lowered.

A high amperage electrical stun is necessary to guarantee induction of

immediate and lasting unconsciousness (Gregory and Wotton, 1987),

whereas high currents also lead to muscle super contractions and subsequent

hemorrhaging in muscle tissue caused by rupture of blood vessels and

damage to muscle fibers (Veerkamp et al., 1987; Gregory and Wilkins, 1989;

Hillebrand et al., 1996). Besides hemorrhages, electrical stunning has been

shown to affect meat quality through its effects on the early postmortem

muscle metabolism (Papinaho and Fletcher, 1996). The effects of electrical

stunning on the rate of rigor mortis development in poultry have been

extensively researched. The effects of various electrical stunning systems on

the rate of early postmortem metabolism (glycolysis, lactic acid

accumulation, ATP depletion, sarcomere lengths, etc.) and the effects on

ultimate muscle pH and meat quality have been reported by numerous

16

authors (including Lee et al., 1979; Thomson et al., 1986; Kim et al., 1988;

Murphy et al., 1988; Papinaho and Fletcher, 1995a, b).

According to Gregory and Wilkins (1989) high current stunning

increases the incidence of red wing tips, broken bones, dislocations,

hemorrhaging of deep breast muscle, and blood-engorged wing veins.

Electrical stunning has also been shown to negatively affect early blood loss

(Kotula and Helbacka, 1966; Kuenzel and Ingling, 1977; Murphy et al.,

1988; Papinaho and Fletcher, 1995a) but not ultimate blood loss (Schutt-

Abraham et al., 1983; Gregory, 1993).

Electrical stunning has been shown to have little effect on breast

muscle pH after 4 to 6 h postmortem (Papinaho and Fletcher, 1996). High

frequency, low voltage electrical stunning has been shown to delay the onset

of rigor mortis, especially when compared to high current stunning (Craig

and Fletcher, 1997) or when compared to postmortem electrical stimulation

(Craig et al., 1999). To determine the effect of electrical stunning on rigor

development and breast meat tenderness, Lee et al. (1979) compared

unstunned control birds to electrically stunned birds. The authors reported

that stunning decreased shear values by 30% on 24-h-old breasts. It was

suggested that delaying rigor development until after spin chilling avoided

the potential for heat shortening, thus resulting in improved meat tenderness.

Papinaho and Fletcher (1996) reported that stunning increased pH until 6 h

postmortem, after which no differences were observed between the stunned

and unstunned controls. The authors concluded that stunning delayed the

onset of rigor for 4 to 6 h, after which no stunning effects occurred.

Research suggests that stunning amperage has a greater deleterious

effect on breast muscle characteristics than voltage. As amperage is

increased, breast muscle hemorrhaging and the incidence of broken bones

increases in broilers (Gregory and Wilkins, 1989b). Increased amperages

17

have also been shown to increase breast muscle hemorrhaging in turkeys

(Gregory and Wilkins, 1989a). In the U.S., where high current stunning is

not commonly used, the incidence of stunning-related defects appears to be

lower. Although electrical stunning is beneficial on a welfare basis, a number

of downgrading conditions were observed in European Union (EU) countries

when high electrical currents were used (Harris and Carter, 1977; Gregory,

1987; Wilkins and Scott, 1987; Veerkamp, 1988; Wabeck, 1988; Gregory

and Wilkins, 1989a, b; Kettlewell and Hallworth, 1990).

The use of high-frequency currents for electrical stunning of poultry

may result in a marked improvement in carcass quality (Wilkins et al., 1998,

1999). In the European Union it is a legal requirement that animals are

stunned prior to killing. A good stun instantaneously induces a state of

unconsciousness and insensibility to pain that lasts until the death of the

animal, immobilizes the animal for easier killing by exsanguinations, and

does not have a negative effect on meat quality.

18

CHAPTER THREE

MATERIALS AND METHODS

3.1: Study area:

The experiment was carried out under commercial conditions in

the processing plant of (ARAPPCO), which lies about 25 km south of

Khartoum.

3.2: Experimental birds:

All birds used in this study were from the same commercial

broiler strain (ROSS 308), 36 day old. Broilers were reared in floor,

feed and water were supplied for ad libitum consumption. The birds

were subjected to 8 hrs of feed withdrawal period prior to slaughter.

Water was provided for ad libitum consumption until catching and

crating. Birds were transported from the farm in crates. There were 10

birds per crate and approximately 3000 birds per vehicle. The duration

of transportation from the farm to slaughterhouse was 30 minutes. The

crates were manually unloaded onto a gravity roller conveyor, which

transport the filled crates to the hanging area where they were hanged

manually in shackles on the moving overhead defeathering conveyor.

A total of 80 birds were randomly selected and divided into four

treatment groups of 20 birds for each: (1) Stunning with 45mA, (2)

Stunning with 35 mA, (3) Stunning with 25mA, and (4) Unstunned

birds as a control.

3.3: Slaughtering procedure:

Birds were processed using on line procedures.First they were

stunned in an electrical water bath stunner (Stork stunner model B-5)

for 7 seconds and the physical activity of each bird was observed

19

immediately after stunning, then the birds were slaughtered using Halal

procedure ( Slaughtering animals in accordance to the Islamic law

“shari’a” , this performed in one of: al zabeh, al naher, al aqer )by rapid

cuts, severing the pipe wind and the major blood vessels in the neck.

The slaughtered birds were then bled for 2 minutes. Under industrial

(commercial) conditions, it was very difficult to weigh all birds before

and after slaughtering, thus four samples of each treatment were

weighed before and after bleeding to determine blood loss, using a

digital balance (Model: bistro ACS - 15JJ) before they were entered to

the scalding tank of 52 ºC for 2 minutes and then they were entered to

the plucking machine for 45 seconds.

3.4: Carcass defects:

After evisceration and before chilling, carcasses were

immediately collected to evaluate carcass defects. The following defects

were recorded: red wing tips, red tail (pygostyle), red feather tracts on

breast and wings, broken bones, wing veins engorgement and feather on

tail, wing or neck. The defects were scored as presence or absence and

the results were expressed as % of carcasses showing the defects.

3.5: Meat quality:

The measurements were taken on the breast which was harvested

from carcasses to detect blood spots on superficial and deep muscles.

Four samples from each treatment were obtained to measure the pH

values, the measurements were taken in 0, 1, 2 and 3 hr post mortem

without chilling, a sample of 5 grams of pectoralis major was harvested

and blended, and 50 millilitres of distilled water was added. The pH of

suspension was measured using a portable pH meter combined with a

glass electrode (Lacom tester, model pH Scan 3, Singapore).

20

3.6: Statistical analysis:

The Complete Randomize Design (CRD), was used as

experimental design, the various data were analyzed using a computer

program (SPSS Program: Version: 11.0.0, SPSS Inc., 2001).Test of

means was done using (Duncan Multiple Range Test) according to Steal

and Torrie, (1980).

21

CHAPTER FOUR

RESULTS

In table (4.1) a significant difference was observed when the

broilers subjected to electrical stunning, this difference appeared

in form of physical activity after stunning(P<0.01) , it was noted

that unstunned birds (0mA) showed the highest level of activity,

followed by 25m A, 35mA, and 45m A, respectively. The results

showed a significant difference (P<0.01) unstunned birds

recorded the highest level of blood spots on the breast meat and

then the level decreases when the current values were 25 mA, 35

mA respectively, whereas the 45 mA recorded the lowest level of

blood spots on the breast meat. A significant difference (P<0.05)

was noted when 25 mA, and unstunned birds recorded the same

level of incidence of feather on wings and tail, followed by 35

mA and 45 mA which was the highest.

The other characteristic (red wing tips, red tail(Pygostyle),

red feather tract on breast and wings, broken bones, wing veins

engorgement, did not show any significant difference.

Table (4.2) indicates that the effect of electrical stunning on

percentage blood loss for broilers bled for 120 second was not

significantly difference.

The effect of electrical stunning on broiler breast muscle’s

pH is showen in table (4.3).It was noted that there was no

22

significant difference between the various levels of electrical

stunning current.

The pH values of the broiler breast muscle at different time

are presented in table (4.4). The pH values were decreased with

increased time, the results showed a significant difference

(P<0.05) between 0,1,2,and 3hour but no significant differences

were recorded between 2 and 3 hour postmortem time.

Table (4.5) shows the effect of electrical stunning and time

on broiler breast muscle pH, the obvious note in this table is that,

the pH values in all electrical stunning current reduced as the time

increased.

23

Table 4.1: Effect of electrical stunning on carcass

characteristics

Treatments (Mean) Parameters

45mA 35mA 25mA 0 mA SEM

Red wing tips 1.00a 1.05a 1.150 a 1.100 a 0.06

Red tail(Pygostyle) 1.40a 1.45a 1.50 a 1.55 a 0.114

Red feather tract on breast 1.80a 1.80a 1.95 a 1.80 a 0.08

Red feather tract on wings 1.50a 1.45a 1.65 a 1.45 a 0.11

Broken bones 1.85a 1.90a 1.90a 1.85a 0.08

wing veins engorgement 1.20a 1.15a 1.05a 1.10a 0.08

physical activity 1.450a 1.800b 1.950b 3.000c 0.12

breast blood spots 1.500a 1.800b 1.850b 2.000 b 0.084

feather on wings, tail 1.650b 1.350a 1.250a 1.250a 0.105

1: Means on the same raw with different letters are significantly

different (p<0.05).

2: Means on the same raw with the same letters are not

significantly different (p>0.05) .

3: mA: milli amperages.

4: SEM: Standard Errors of Treatment Means.

24

Table 4.2: The effect of electrical stunning on percentage blood loss

for broiler chicken bled for 120 seconds.

Treatment Mean ± SE number

45mA 2.502a ±0.284 4

35 mA 2.887a ±0.282 4

25 mA 2.725a ±0.274 4

0 mA 2.347a ±0.316 4

Means with the same superscript are significantly not different (p>0.05)

SE: Standard Error.

25

Table 4.3: The effect of electrical stunning on broiler breast

muscle pH.

Treatment Mean ± SE

0 mA 5.226 a±0.029

25 mA 5.261 a±0.029

35 mA 5.261 a±0.029

45 mA 5.252 a±0.029

Means on the column with the same superscript are not significantly

different (p>0.05).

mA: milli amperage.

SE: Standard Error.

26

Table 4.4: The effect of electrical stunning on broiler breast

muscle’s pH at different postmortem times.

TIME (h) Mean ± SE

0 5.374c±0.029

1 5.282b±0.029

2 5.194a±0.029

3 5.149a±0.029

Means on the column with the same superscript are not significantly

different (p>0.05).

SE: Standard Error.

27

Table 4.5: The effect of electrical stunning and time on pH.

Treatment (mA) TIME(h) Mean ± SE

0 5.392±0.058

1 5.245±0.058

2 5.157±0.058 0

3 5.107±0.058

0 5.350±0.058

1 5.305±0.058

2 5.207±0.058 25

3 5.180±0.058

0 5.328±0.058

1 5.277±0.058

2 5.250±0.058 35

3 5.188±0.058

0 5.425±0.058

1 5.300±0.058

2 5.163±0.058 45

3 5.122±0.058

NS: Not Significant

SE: Standard Error. mA : milli amperage.

28

CHAPTER FIVE

DISCUSSION

The physical activity of the birds after stunning was increased with

the decreased current level applied ,this result disagree with the work of

(Gregory and Wilkins,1989) who found that violent contraction was

associated with high amperage (>100 mA) electrical stunning as conducted

in the European Community.

The study also found that increased electrical stunning current is

negatively related to the decreasing of the incidence of breast blood spots.

Such results is not in line with the study of (Gregory and

Wilkins,1989b)who found that when amperage is increased, the incidence

of breast muscles hemorrhaging increases in broilers.

Feather release was measured after mechanical plucking operation

by counting the number of carcasses with feathers or feather shafts left on

the wing and tail. The results showed that the presence of feather was

affected by the increasing of electrical stunning current, the findings

showed that when the electrical current decreases, the incidence of feather

is also decreased . These results were in agreement with the previous study

which was implemented by (Dickens and Shackelford, 1988), it indicated

that, in the U.S.A. poultry industry, low current (10 to 45 mA) electrical

stunning is primarily used to decrease feather release force .

The incidence of red wing tips and red tail in stunned birds was

reduced when the current increases, these results did not agree with the

previous studies which indicate that as the stunning voltage is increased,

the incidence of red wing tips and red tail is increased (Veerkamp and de

29

Vries,1983).Similar results were noted by the study of (Gregory and

Wilkins,1989a.b,c) who found that, the incidence of red wing tips increases

when the electrical stunning was applied.

The findings of the current study indicated that electrical stunning

clearly does not affect the incidence of red feather tract on breast or wings.

Such results were cited.

The incidence of broken bones was not significantly affected by the

implementation of electrical stunning, these results do not support the

statement that show increasing effect of higher electrical currents on the

incidence of broken bones, these statements were reported by Wilkins and

Scott, (1987), Gregory and Wilkins,(1989a,1990),and Walther(1991) who

reported that broken bones, could be reduced if the stunner voltage was

lowered.

From this study, the implementation of electrical stunning result in

increased blood-engorged wing veins when the current increased.Such

results were obtained from previous studies conducted by Gregory and

Wilkins, (1989).

After neck cutting, chickens lose between 35 and 50% of their total

blood which is about 4% of live weight (Newell and Shaffner, 1950). In

this experiment, stunned birds lost between 2.5 and 2.9% of their BW in a

2- minutes bleeding time. While unstunned birds lost 2.4% of their BW in

a 2-minutes bleeding time. These results showed that electrically stunned

birds had the highest blood loss, compared with unstunned birds which

showed the lowest bleed-out percentage, these findings are not in line with

the results of (Kotula and Helbacka,1966;Kuenzel and Ingling

,1977;Schutt-Abraham et al.,1983;Veerkamp and de Vries,1983;Murphy et

al.,1988;Ppinaho and Fletcher ,1995a), which indicated that electrical

stunning has been associated with a decrease in carcass blood loss. Recent

30

works suggest that the effect of electrical stunning only on the rate of early

blood loss,but it has little effect on the ultimate carcass blood loss(Schutt-

Abraham et al.,1983;Gregory and Wilkins,1989d; Papinaho and Fletcher

,1995b).

Muscular activity accelerates glycolysis,causing the accumulation of

lactic acid in the muscles tissue thus lowering pH(Khan and

Nackamura,1970). In this study results had no significant reduction in pH

levels,this may be due to (absence of cooling of meat). These findings are

not in agreement with the previous results as recorded by(Gregory et

al.,1991;Wilkins et al., 1998;Sante et al.,2000) who found that high

stunning currents causes increased rate of postmortem pH decline and

improved meat quality, and the results are not in accord with results from

(Papinaho and Fletcher,1996) who noted that electrical stunning has been

recorded to cause little effect on breast meat pH after 4 to 6 hours

postmortem. Whereas in this study the effect of electrical stunning on

breast meat pH has a significant effect with time, the pH decline as

postmortem time increased until 4 hours postmortem.

In conclusion, many factors present in commercial processing plant

may contribute to the incidence of broiler carcass’ defects. Under

commercial conditions, it is extremely difficult to isolate the effects of

electrical stunning from that caused by other factors such as catching,

transportation, hanging, wing flapping, type of cut (slaughter), efficiency of

bleeding, and picking. Depending on the results of the current study the

following recommendation should be taken into consideration:

Based on these results obtained from this study, the level of 45mA

showed the lowest incidence of carcass defects and recommended to

be in use, but other experiments on the levels of this study must be

done to confirm these results or to achieve the best results.

31

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40

APPENDEX

ANALYSIS OF VARIANCE

NS: Not Significant * : Significant at 0.05 **: Highly Significant at 0.01

Source Dependent Variable df Mean Square F Sig.

Red wingtips 3 0.008333 1.195 NS .317 Red tail (Pygostyle) 3 0.008333 .321 NS .810 Red feather tract on breast 3 .112 .810 NS .492

Red feather tract on wings 3 .179 .700 NS .555

Broken bones 3 0.001667 .146 NS .932 Wing veins engorgement 3 0.008333 .745 NS .529 Physical activity 3 8.900 35.414** .000 Breast blood spots 3 .879 6.216** .001

Treatment

Feather on wings, tail 3 .717 3.281* .025 Red wingtips 76 0.006974 Red tail (Pygostyle) 76 .259 Red feather tract on breast 76 .139

Red feather tract on wings 76 .256

Broken bones 76 .114 Wing veins engorgement 76 .112 Physical activity 76 .251 Breast blood spots 76 .141

Error

Feather on wings, tail 76 .218

41

PHOTO (1). Broiler breast meat with blood spots as a result of applying 45mA of

Stunning current.

42

PHOTO (2). Broiler breast meat with blood spots as a result of applying 35 mA of

Stunning current.

43

PHOTO (3). Broiler breast meat with blood spots as a result of applying 25 mA of

Stunning current.

44

PHOTO (4). Normal piece of breast meat from properly unstunned broiler.

45

4535250

Mea

n pH

5.5

5.4

5.3

5.2

5.1

5.0

Time (hrs)

0

1

2

3

Treatments

Fig. (1) The effect of treatment and time on pH

46

unstunned25ma35ma45ma

Blo

od lo

ss %

2.9

2.8

2.7

2.6

2.5

2.4

2.3

Treatments

Fig (2) Effect of electrical stunning on blood loss %

47

unstunned25ma35ma45ma

Mea

ns o

f bre

at b

lood

spot

s

2.1

2.0

1.9

1.8

1.7

1.6

1.5

1.4

Treatments

Fig (3) Effect of electrical stunning on breast blood spots

48

unstunned25ma35ma45ma

Mea

ns o

f phy

sica

l act

ivity

3.5

3.0

2.5

2.0

1.5

1.0

Treatments

Fig (4) Effect of electrical stunning on physical activity