Metabolism Assignment 1 - 15% of final marks

How does the digestion system of your chosen animal break down food i.e. conversion of food protein to animal protein?

Nutrition and Metabolism of the Cow: Digestive System of the Cow.

Proper nutrition is the foundation for a productive and profitable cow herd. Unaccompanied with good nutrition, cattle can’t express their full potential including reproductive efficiency.

Cattle are classed as ruminants, they have four compartments to their stomach and chew their cud. The cattle digestive system evolved to be able to handle large volumes of material. Dairy farming is a crucial part to Australia’s rural industry. On farm efficiency is on an increase through the improvement of pasture and feed and also herd management techniques.

Supplement the cattle diet with grains and other legumes is becoming increasingly common, the Australia’s dairy industry remains predominantly pasture based. State’s of Australia, Victoria foremost, have attainable milk productions, supplying fresh milk to nearby cities and towns. The industrial value increases through the processing of milk to produce fresh lines such as butter, cream, cheese and yogurt. Bulk milk and specialised powdered milks are also significant. (Crampton, E.W, Harris, L.E (1969) “A Series of Books in Agricultural Science - Animal Science” (W.H Freeman and Company - San Francisco))

Cattle feed can be classed as either roughages (high fibre plants / the fibrous part of the plant) or concentrates (compound feed mix of grain and by products also may have the addition of minerals)(Edwards, R.A, Greenhalgh J.F.D, McDonald, P (1981) “Animal Nutrition - 3rd edition” (Longman Group Limited)). Ruminant are known to be capable of utilising roughages because they have micro-organisms that can breakdown the resilient component of fiber. Monogastrics (simple stomach animals) don’t contain a rumen neither the microorganisms to break down the resilient fiber particles, and therefore, can’t efficiently use roughages. Concentrates are feeds that are low in fiber and high in energy. These generally consist of grains, plant and animal by products, diet of monogastrics mainly consists of concentrates such as corn or soybean meal (Edwards, R.A, Greenhalgh J.F.D, McDonald, P (1981) “Animal Nutrition - 3rd edition” (Longman Group Limited)).

The multiple circumstances that may affect an animal's nutritional needs. Palatability which refers to the flavour, texturisation, and overall satisfaction with the taste, is exceptionally important to the animal's interest in food, age and production state of the animal is also important. The age variation between animals, also impacts the nutritional needs of there diet. Impregnated animals (gestating) or producing milk (lactating) have higher protein requirements than non pregnant or non lactating animals, and animals that have working requirements have different protein and energy requirements. (Bedford, P.G.C, Payne, J.M, Price, C.J, Sutton, J.B, (1989) “Metabolic and nutritional diseases of cattle” (Library of Veterinary Practice))

Feed condition is of significant relevance as if the feed is compromised ie: feed that is affected by a micro-organism such as fungi or bacteria therefore leading to degradation it will not be acceptable to the animal. Overall health of the animal or herd will affect an interest in food, it is likely that sick animals will not eat as much as healthy animals, all of these factors affect an animal's nutritional level. (Edwards, R.A, Greenhalgh J.F.D, McDonald, P (1981) “Animal Nutrition - 3rd edition” (Longman Group Limited)).

The nutritional needs of dairy cattle typically consists of fibrous plant’s material that requires prolonged chewing, fermentation and soaking before its nutrients are available for digestion and absorption. A cows digestive system has significantly evolved to contain multiple compartments in which these processes take place are ‘four stomachs’, of which there are three: the rumen, the reticulum and the omasum. The stomach proper, corresponding to the simple mono-gastric stomach, is called the abomasum (Girard CL, Lapierre H, Matte JJ, Lobley GE (2005) Effects of dietary supplements of folic acid and rumen-protected methionine on lactational performance and folate metabolism of dairy cows. Journal of Dairy Science 88, 660-670.)

Fore-stomach otherwise known as reticulorumen - fermentation occurs at this point of digestion it is constituted of two distinct areas called the reticulum and the rumen. Reticulum has a distinctive function as it aids to help bring boluses of feed (known as cud) back up to the mouth for re-chewing. Reticulorumen may also serve as a holder for heavy foreign objects that a dairy cow may eat. This may lead to a condition known as "Hardware Disease"- a metal object such as wire or a nail is swallowed and punctures the reticulum wall, this could be lethal as, the protozoa & bacteria can contaminate the body cavity resulting in peritonitis (inflammation of the peritoneum) and, the heart and diaphragm may be punctured by the object causing failure of these tissues. (Bedford, P.G.C, Payne, J.M, Price, C.J, Sutton, J.B, (1989) “Metabolic and nutritional diseases of cattle” (Library of Veterinary Practice))

Rumen is, by far, the largest compartment of the digestive system as it stores large quantities of feed, and mixes the feed with strong contractions, it is also a suitable environment for the protozoa
& bacteria to live. Microorganisms like the rumens environment as it’s constant temperature and pH provides ideal conditions for growth and functionality it keeps this constant by removing many of the waste products, majority of which are volatile fatty acids (Crampton, E.W, Harris, L.E (1969) “A Series of Books in Agricultural Science - Animal Science” (W.H Freeman and Company - San Francisco)). Volatile fatty acids are the primary sources of energy for the cow, absorbed via thousands of "finger-like" projections lining the bottom and sides of the rumen wall, they can vary between half inch long and they increase the surface area of the rumen so as to increase her ability to absorb volatile fatty acids (Edwards, R.A, Greenhalgh J.F.D, McDonald, P (1981) “Animal Nutrition - 3rd edition” (Longman Group Limited)).

Feed may have been reduced in size by chewing and digestion by the micro-organisms it then passes into the third compartment called the omasum. It appears that of an open book with three sides bound, they contain small papillae which allow for the absorbance of a large portion of the volatile fatty acids that were not absorbed through the rumen wall. Electrolytes such as potassium and sodium are likely absorbed here as well therefore dry out the feed before entering the next compartment (Edwards, R.A, Greenhalgh J.F.D, McDonald, P (1981) “Animal Nutrition - 3rd edition” (Longman Group Limited))

The last compartment to make up the cattle stomach is known as the abomasum or "true" stomach as it functions similarly to the stomach of people and pigs. Similar to the omasum, the abomasum contains many folds to increase its surface area. Abomasum wall secretes enzymes and hydrochloric acid, serving primarily in the acid hydrolysis of microbial and dietary protein, preparing these protein sources for further digestion and absorption in the small intestine. pH is approximately 6.0 but is lowered to approximately 2.5 by acid secretion, therefore creating a sustainable environment for the enzymes to function. Main digestive function of the abomasum is the partial breakdown of proteins, which is done via the enzyme pepsin (Annenkov, B.N, Georgievskii, V.I, Samokhin V.T, (1982) “Mineral nutrition of animals”).The formation of peptides (small units) is brought about by the function of micro-organisms in the rumen from feed proteins, this breakdown occurs before leaving the abomasum.

The small intestinal tract, is a one hundred and thirty foot long, and two inch wide tube, food enters the small intestine, it combines with secretions from the pancreas and liver which elevate the pH from 2.5 to approximately 7 or 8. An increase in the pH is necessary for optimal function of enzymes. Sequentially for feed to become of sufficient use to the cow, they must be degraded into smaller molecules. This occurs via enzymes that reduce any remaining protein to amino acids, starch to glucose, and complex fats into fatty acids, majority occurs in the small intestine using enzymes and hormones from the pancreas, liver, and small intestine (Annenkov, B.N, Georgievskii, V.I, Samokhin V.T, (1982) “Mineral nutrition of animals”). The absorption of nutrients usually takes place in the lower half of the small intestine, the intestine wall contains a substantial amount of "finger-like" projections called villi that function by increasing the surface area of the intestine to assist in the absorption process. Contractions of the muscular intestinal wall aid in mixing the digested material and moving it down.

Cecum, colon, and rectum, are collectively referred to as the large intestine. It’s primary purpose is to absorb water from the digested food matter thereby making it more solid. Bacterial micro-organisms residing in the intestine work at digesting any food which elude digestion earlier (Annenkov, B.N, Georgievskii, V.I, Samokhin V.T, (1982) “Mineral nutrition of animals” ).

Sustainable Animal Production can be defined as the production that should meet the needs of the current generation without affecting the ability of future generations to meet their own needs (Oltjan & Becket, 1996; UN, 1987; Vavra 1996). Ruminant’s have a crucial part in the supply of high quality food’s like meat and milk for the human population. Animal production systems of feed are important as they require less or no cereal grains which are an essential energy source for humans (Oltjan and Beckett, 1996). Rumen/s which act as a fermentation vat to convert in-digestible fibrous materials in to high quality food such as milk and meat, fibrous materials are abundant in availability as renewable resources from pastures, trees, forests, woodlands, crop residues and other agricultural industrial by-products. The conversion of these cellulose rich waste products by the naturally inhabiting rumen microbes into high quality food is a highly desirable feature which should be harnessed to utilise fibrous byproducts and achieve sustainable animal production. The ruminants also contribute to the fertility of soils through their faeces and urine and so transform some unproductive lands for their productive use to produce food or cash crops for the human population.

While at looking at the digestive system, monogastrics and ruminants appear similar, in reality this is not the case. Though both ingest primarily large amounts of fibre, their digestive systems vary greatly (Frandson, Wilke, & Fails, 2006). The major difference is obviously the rumen in ruminants, which functions as the fermentation chamber, rather than the large intestine in monogastrics (Frandson, Wilke, & Fails, 2006). Because of this, the majority of a ruminants digestion will have already been fermented by the microbes in the rumen before it reaches the stomach for enzymatic digestion (Frandson, Wilke, & Fails, 2006). Ruminants also "chew the cud, aiding in their easy digestion of fibre (Frandson, Wilke, & Fails, 2006).

References:

Annenkov, B.N, Georgievskii, V.I, Samokhin V.T, (1982) “Mineral nutrition of animals”

Crampton, E.W, Harris, L.E (1969) “A Series of Books in Agricultural Science - Animal Science” (W.H Freeman and Company - San Francisco)

Edwards, R.A, Greenhalgh J.F.D, McDonald, P (1981) “Animal Nutrition - 3rd edition” (Longman Group Limited)

Girard CL, Lapierre H, Matte JJ, Lobley GE (2005) Effects of dietary supplements of folic acid and rumen-protected methionine on lactational performance and folate metabolism of dairy cows. Journal of Dairy Science 88, 660-670. Available on-line through library http://0-search.proquest.com.alpha2.latrobe.edu.au/docview/195823997/fulltextPDF/13F50A1A797C3537A7/9?accountid=12001

Girard CL, Matte JJ (2005) Effects of intramuscular injections of vitamin B12 on lactation performance of dairy cows fed dietary supplements of folic acid and methionine. Journal of Dairy Science 88, 671-676. Available on-line through library http://0-search.proquest.com.alpha2.latrobe.edu.au/docview/195810633/fulltextPDF/13F50A1A797C3537A7/10?accountid=12001

Graulet B, Matte JJ, Desrouches A, Doepel L, Palin MF, Girard CL (2007) Effects dietary supplements of folic acid and vitamin B12 on metabolism of dairy cows in early lactation. Journal of Dairy Science 90, 3442-3455. Available on-line through library http://0-search.proquest.com.alpha2.latrobe.edu.au/docview/195811812/fulltextPDF/13F50D313973AC4E3E8/41?accountid=12001

National Research Council, Subcommittee on Mineral, Toxicity in Animals (1980) “Mineral Tolerance of Domestic Animals” (National Academy of Science - Washington D.C)

Bedford, P.G.C, Payne, J.M, Price, C.J, Sutton, J.B, (1989) “Metabolic and nutritional diseases of cattle” (Library of Veterinary Practice)

Church, D.E. 1984. Livestock Feeds and Feeding. Corvallis: O&B Books.

Ensminger and Olentine. Feeds and Feeding. Clovis: Ensminger Publishing Company.

Sisson and Grossman. The Anatomy of the Domestic Animals.