The nutritionist vol 1 issue 2

The Animal Nutritionist

The Small Ruminant Edition Research and Development Division MINISTRY OF AGRICULTURE AND FISHERIES Volume 1 Issue 2

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 Animal Nutritionist | Volume 1 Issue 2

The Complexity of Ruminant Digestion

1

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

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.

The Animal Nutritionist | Volume 1 Issue 2

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

2

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 Animal Nutritionist | Volume 1 Issue 2

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

3

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.

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 Figure 1 shows the grazing habits of local ruminants.

The Animal Nutritionist | Volume 1 Issue 2

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

4

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 The Animal Nutritionist | Volume 1 Issue 2

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

5

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

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

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.

The Animal Nutritionist | Volume 1 Issue 2

costs and at the same time increase production.

6

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 The Animal Nutritionist | Volume 1 Issue 2

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

7

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)

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

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

The Animal Nutritionist | Volume 1 Issue 2

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

8

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 Animal Nutritionist | Volume 1 Issue 2

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

9

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 nonprotein 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.

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

The Animal Nutritionist | Volume 1 Issue 2

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

10

The Animal Nutritionist | Volume 1 Issue 2

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

11