MINISTRY OF AGRICULTURE AND FISHERIES

Volume 1 Issue 2

The Animal Nutritionist

The Small Ruminant Edition Research and Development Division

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The Animal Nutritionist

Your portal to up-to-date information on farm animal nutrition

Guest Editor’s Note

Small ruminant production in Jamaica has been on the increase in order to meet increased

demands for sheep and goat meat. This creates an opportunity for farmers to become engaged

in a viable enterprise, thus having a regular source of income.

In this regard, proper nutrition is essential for the health and production of animals and is the

basis of successful production systems.

A well planned and executed preventive health programme cannot overcome problems that are

created by poor nutrition nor can advanced reproductive technologies overcome nutritional

limitations of reproduction. Therefore, nutrition of small ruminants is of paramount importance

for successful small ruminant production.

I therefore emphasize that in your small ruminant production system; make nutrition your main

priority.

Dwight McKie

Livestock Research Officer

The Complexity of Ruminant Digestion

By Tanika O’Connor-Dennie, PhD and Jinte Blistra, MSc

The unique digestive system of ruminants is a result of thousands of years of evolution and

allows ruminants to survive on average to poor quality feed (high fibre and low protein). Their

feeding strategy is simple: Do not spend a lot of time and energy searching for food but

instead eat enormous quantities of stationary and abundant vegetation. This vegetation is rich in

fibre that is not degradable by mammalian enzymes and therefore hardly digestible by

carnivorous and omnivorous animals. The secret of the ruminant’s success lies in its ability to

use symbiotic micro-organisms that can ferment fibre into energy rich by products.

The symbiotic relationship between micro-organisms and their host requires a complex

digestive system that can facilitate fibre fermentation. Fibre can be found in the cell wall of plant

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Figure 1: Overview of the digestive tract of a goat.

cells and it consist of structural carbohydrates (cellulose and hemicellulose) and other

compounds (lignin) that cannot be digested by enzymes in the digestive tract of animals. Some

herbivores, like horses, have an enlarged cecum and colon which enables them to digest

fibrous feeds, but these animals are not as efficient in fermenting fibre as ruminants. Ruminants

are built to feed on high fibre diets and their digestive system shows many adaptations to get as

much energy and nutrients from the low quality feed as possible.

In order to understand the complexity of ruminant digestion and fibre fermentation we must

understand the function of several parts of the digestive tract specific to ruminants. Figure 1

gives an overview of the digestive tract of a goat. It all starts in the mouth where initial grinding

and wetting of the food takes place and saliva plays an important role in this process. The

salivary glands of sheep produce about 15 litres of saliva per day and it has two very important

functions besides lubricating: (1) saliva provides the fermentation vat with fluid and (2) saliva is

used as a buffer against the large

quantity of acid produced in the rumen.

After the food is swallowed it will enter

the rumen and reticulum through the

oesophagus. In these first two sections of

the fore stomach the food is further

wetted and bacteria become attached to

food particles and secrete enzymes to

break down cellulose and hemicelluloses

fromthe plant cell walls. Then a process

will take place that is specific for

ruminants which is called ruminating. The

animal will bring up the plant material

that is now partially digested and it will chew the food again to break down the tough cell walls

even more. Also, re-chewing the food will stimulate saliva production to keep the food wet and

to provide more buffers against the acids formed by the bacteria.

The ruminated plant material will find its way back again into the rumen and reticulum. These

two compartments are often considered as one since free exchange of contents is possible. In

this large vat the masticated and wetted forage is kept for several hours to days while the

bacteria begin to digest the material along the breaks and tears caused by chewing and

ruminating. The bacteria in the rumen are anaerobic, which means that these organisms do not

require oxygen.

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Other animals also make use of anaerobic bacteria in their digestive tract, but the main

difference between the bacteria in ruminants and those in other animals is the quantity. Rumen

fluid can have a million to ten million bacteria per milliliter of fluid and all bacteria break down

the plant material ingested by ruminants. The major product of fermentation is energy in the

form of fatty acids including acetic acid, propionic acid, and butyric acid. The bacteria will use

the fatty acids for energy for themselves or the fatty acids will be absorbed through the cells of

the rumen wall as energy for the host. Other products of fermentation include vitamin K, all

amino acids and B vitamins.

All fermentation of feed takes place in the rumen and reticulum after which it will pass through

the omasum. The function of the omasum is not entirely clear, but it seems as if this

compartment serves as a sieve since it prevents coarse fibre particles from passing through.

This will allow the larger particles, which are likely to contain considerable amounts of

fermentable substrate, to be further digested. Some absorption of water and VFA will take place

while this muscular stomach compartment moves the digesta into the final stomach, the

abomasum.

The abomasum is the ruminant’s “true stomach” and is very similar to the stomach of

monogastrics. In the abomasum gastric juices, including hydrochloric acid and the enzyme

pepsin, are being produced which are necessary to digest protein. Due to a high level of acid in

the abomasum, the bacteria in the digesta are not able to survive and the bacterial cell walls will

successfully be broken down by another enzyme called lysozyme.

The lower gastrointestinal tract of ruminants is again similar to that of monogastrics. Remaining

proteins are broken down in the small intestine and vitamins and minerals are being absorbed.

Some plant fibres may have escaped breakdown along the tract, but when these fibres reach

the cecum and colon another population of anaerobic bacteria will digest and ferment them and

this gives the ruminant a last chance to derive as much energy from their feed as possible.

Overall it can be said that the digestive system of ruminants is very complex. Ruminants are

specialized animals that can get energy from high fibrous forages due to evolutionary

adaptations in their digestive system; adaptations that cannot be found in any other animal

group. Understanding the complex process of digestion in ruminants is one of the first steps to

improve ruminant nutrition and hereby production.

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Classification of Ruminants According to Diet Choice

By Jinte Blistra

Ruminants encompass a large part within the category herbivores as there are about 150

different domestic and wild ruminant species including cows, sheep, goats, deer, buffalo, bison,

giraffe, moose and elk. These animals have been classified as ruminants due to specific

characteristics that they have in common including the practice of ruminating, the possession of

a four compartment stomach, and the dependence on symbiotic microbes to break down

structural carbohydrates. However, even though the digestive physiology of all ruminants

appears very similar it is the differences that we need to pay attention to in order to optimize

feeding practices of ruminants.

The differences in feeding behaviour, digestive physiology and anatomy between ruminant

species can be explained by the characteristics of food that is available. Plants show high

variability in morphology and chemistry which has led to many adaptations within the group of

ruminants. A clear distinction in plants can be made between grasses and browses/shrubs (like

shrub leaves and stems). In general, grasses have a thicker cell wall than browses and their cell

walls mainly consist of slowly digestible plant fibres such as cellulose while browses contain

less cell walls and are therefore easier to break down.

These differences in plant characteristics have forced ruminants to adapt in different ways. One

group has adapted to efficiently digest grasses that are high in fibre while another group has

specialized in digesting browses that are lower in fibre and higher in protein. According to this

concept ruminants have been classified in three different groups: concentrate selectors (also

known as browsers), intermediate feeders, and grass/roughage eaters (also known as grazers).

Figure 1 shows the grazing habits of local ruminants.

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The major difference between the groups lies in the animal’s natural feed choice or more

specifically their preference for grass or browse. Concentrate selectors naturally consume a diet

that consists of at least 75% browse while grass/roughage eaters consume a diet that consists

of less than 25% browse. Intermediate feeders change their feeding behaviour according to the

availability of forage which is highly dependent on season. From figure 1 it can be seen that

sheep and goat do not fall under the same category. Instead sheep, similar to cattle, are

grass/roughage eaters while goats on the other hand are intermediate eaters which indicate that

goats are more flexible in their diet choice.

The differences in plant characteristics have led to various feeding strategies in ruminants and

as result they show different specializations of the digestive tract which allows grazing and

browsing species to optimize extraction of nutrients from their feed. Grazers, which will feed on

high fibre grasses, generally have a larger, more muscular, subdivided rumen/reticulum and a

smaller opening between the reticulum and omasum than browsers. These adaptations will slow

down the passage of digesta to the lower tract which gives grazers more time for the

fermentation of plant fibre. As a result grazers are able to digest cell wall more thoroughly and

obtain more energy per unit of food.

In browsers on the other hand, digesta will move rapidly through the tract due to the fact that

browse contains less cell walls and the fibres within the cell walls are more lignified and

indigestible. As a result browsers have a smaller rumen, which allows a rapid flow of digesta,

and the rumen contains an extensive dense layer of papillae that enlarges the surface of the

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rumen by 22 times. This dense layer of papillae allows efficient absorption of VFA’s (volatile

fatty acids) from the rapidly fermenting cell contents of browse. Also, browsers tend to have a

larger abomasum, cecum and intestines which suggest that browsers rely more heavily on

direct digestion in the true stomach and lower digestive tract than grazers.

Many other differences can be distinguished between browsers and grazers including

differences in salivary glands, liver size, mouth characteristics, and teeth size but the most

important differences have been described above: There seems to be a clear relationship

between plant characteristics and different nutritional needs in ruminant species and

understanding this concept could allow farmers to optimize production by increasing utilization

of their land.

Mixed grazing is a perfect example of benefitting from the differences in feeding behaviour

between ruminant species. Large unselective feeders, like cattle, will mainly feed on grass,

while smaller and more selective species like goats are able to change their diet according to

availability of forage which is mostly dependant on seasonality. In dry seasons goats can

maintain their body weight by feeding on bushes, like acacia (commonly called casha) bushes

which will not be consumed by cattle. A system like this will not only increase the production per

unit area, it will also be very effective against the problem of bush encroachment in pastures.

Also, by understanding the nutritional needs of ruminant species locally available forages could

be better utilized to optimize feeding rations of ruminants, in particular sheep and goats.

Mulberry (Morus spp), leucaena (Leucaena leucocephala) trichanthera (Thrichanthera

gigantea), quick stick (Gliricidia sepium), and moringa (Moringa oleifera) are examples of locally

available browse that have the ideal nutrient composition and show high palatability and

digestibility, especially in goats. Exploiting these readily available forages could reduce feed

costs and at the same time increase production.

In conclusion, it is important to be aware of the differences in feeding strategies between

ruminant species as this can create opportunities to increase production. Benefitting from mixed

grazing systems that could significantly increase the production per unit area as well as

exploiting locally available forages for browsing species (like goats) are only 2 examples of

ways to improve local farming strategies. For many farmers it could be worthwhile to reassess

their farm plan and exploit the information presented in this article by applying this theory into

practice.

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General Introduction to Small Ruminant Nutrition

by Tanika O’Connor-Dennie, PhD

Small ruminant production (sheep and goats) has significantly increased in Jamaica over the

last decade. With the introduction of improved genetics through the importation of the Boer

goats and Dorper sheep, comes the need to better understand the nutritional requirements of

these animals. A complete understanding to the nutritional requirements of these animals that

have a higher potential for weight gain (compared to locally available breeds) ensures that

weight gain is maximized without wasting nutrients.

There are five nutrients that must be taken into consideration when developing a complete

nutrition programme for your flock, they are:

1. Water

2. Energy

3. Protein

4. Minerals

5. Vitamins

One additional item can be added, making the list six, and that is fibre/roughage. This article will

only focus on the role water, energy, protein and fibre plays in small ruminant nutrition.

Water

The nutrients are listed in the order of importance for survival in ruminants. Indeed, water is

frequently taken for granted but constituents over 60% of body composition. Whereas sheep

and goats can afford to lose up to 50% of their body protein and 90% of their body fat, just 10%

of water loss is fatal. That’s because water is vital to almost all bodily functions ranging from

temperature control, nutrient transport and acting as a conduit for chemical reactions. It is

recommended that each ewe or doe have at least 1 foot of water through space, which ideally

should be paved to prevent unsanitary conditions and foot-rot. Physiological conditions such as

pregnancy and lactation increases water consumption, with water intake doubling during the last

month of gestation.

Here are the guidelines regarding water intake:

Animals’ water intake should be 2-4 times dry matter intake

Animals should have approximately 3.5-7 litres/day (1-1.5 gallons)

Lactating females should have twice as much water (7-15 litres or 2-4 gallons per day)

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Energy

Energy is the first limiting component in a diet of all livestock animals. As such animals first eat

to meet their energy requirement, then their protein, mineral and vitamin requirements. The

amount of energy sheep and goats require is dependent on the level and stage of production.

Therefore a growing lamb requires a more energy dense diet compared to a ewe that is not

nursing or lambing. It is therefore recommended that animals experiencing rapid periods of

growth, lactation and lambing receive a more energy dense diets in the form of concentrates

and very high quality forages compared to animals that are at maintenance. When animals that

are in a higher stage of production receive diets low in energy they not only experience reduced

growth rates but have lower body scores (ribs and hip bones distinctly visible), poor immune

system and a higher incidence of parasitic diseases (worm infestation).

Because majority of the energy consumed by both sheep and goats come from the breakdown

of roughage (grass and hay), this should be the major component of their diets, this energy is

either expressed as calories or total digestible nutrients (TDN) as a percentage of the feed on

concentrate feed tags and literature. Currently, feed and forage testing at Bodles Research

Station estimate TDN using the Van Soest fibre analysis.

The most common choice for energy supplementation is cereal grains such as corn which

comprises the majority of concentrate feeds. Corn is dense in energy, and most of that energy is

in the form of starch. Consumption of high levels of corn decreases in forage intake and

digestibility in sheep and goats. This however does not affect their energy status because of the

energy from the corn. Unlike corn, wheat middlings (by-product of flour production) does not

suppress fibre digestion and may increase hay digestibility. Often these by-product type feeds

are much more economical than corn. Another source of energy supplementation is fat which

should not exceed 8% of the diet, or 4% to 5% as supplemental fat.

Protein

After meeting their energy needs, small ruminants require a minimum of 7% dietary crude

protein for normal rumen bacterial growth and function. Anything below 7% CP decreases feed

intake digestibility. Like humans, protein deficiency is associated with decreased growth,

decreased immune function, anaemia, depressed feed use, oedema, and death in sheep and

goats.

The type of plant (legumes like cowpeas and wild tamarind have 20-28% CP versus cereal grain

with 7-8% CP), soil fertility, season and vegetative state (protein content of plants declines with

maturity) affects the CP content. Similar to energy needs crude protein requirements vary with

the animal’s stage of production. For maintenance, a 75-kg (165 lbs) ewe requires a diet

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containing 8% to 9% protein, and a 55-kg doe needs a diet with 7% to 8% protein. During

lactation both the ewe and doe require in excess of 13.5% protein, depending on the number of

offspring suckling and level of milk production. Animals at maintenance do not require

additional supplementation beyond well maintained pasture, whereas heavy producing animals

may require supplemental protein. The most consistent sign of protein deficiency in lactating

animals is poor weight gain or slow growth in their lambs or kids, particularly for twins or triplets.

Non-protein nitrogen (NPN) is an inexpensive way to increase the protein concentration of

rations for sheep or goats. NPN is any source of nitrogen in the non-protein form, but the most

commonly used type is urea.

Fibre

Fibre is an important component of the diet of a ruminant animal. Without adequate fibre in the

diet, normal rumination does not occur. In wool producing sheep, feeding a concentrate-based

diet with limited amounts of fibre results in “wool pulling” as the animals seek a roughage

source. To promote a healthy rumen, the dietary fibre content should generally be greater than

50%. Fibre also is required in the diet to maintain acceptable levels of milk fat. It is generally

suggested that a minimum particle size of 1 to 2.5 cm be fed to stimulate normal rumination.

Pelleted roughage does not meet the requirement for fibre size. Animals being fed pelleted

forage or lush pasture should be offered hay.

Nutrition Facts

Feeding Urea as a Non-Protein Source of Nitrogen

by Tanika O’Connor-Dennie, PhD

The following rules of thumb are useful when feeding urea as a protein source:

1. Never use urea for more than one third of the protein in the diet or 3% of the grain portion of

the diet.

2. Ensure that a highly fermentable source of carbohydrates (e.g., corn) is fed along with non-

protein nitrogen (urea and poultry little).

3. Avoid the sudden introduction of urea into the diet (allow at least 8 to 10 days for its

introduction).

4. Ensure proper mixing of feedstuffs whenever urea is used.

5. If 1 pound of urea and 6 pounds of ground corn are cheaper than 7 pounds of soybean meal

(SBM), then the former diet may be efficiently fed. However, if 7 pounds of SBM is less

expensive, the urea should be avoided.

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6. If the crude protein of the diet is greater than 14% of the dietary total digestible nutrient, NPN

is of little value.

For example, if TDN is 45%, NPN is of limited or no value if the crude protein of the diet is

greater than 6.3% (45 x 0.14 = 6.3).

7. Because of varying dietary intakes and their relationship to body condition scoring (BCS),

NPN is best used in sheep or goats with body condition scores greater than 2.5; they should be

avoided in animals with a body condition score of less than 2.

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Photos from the Meat Goat Production Handbook, Langston University, 2007