FEEDING VALUES

Gisborne Herald, Volume LXXIV, Issue 22320, 3 May 1947, Page 8

FEEDING VALUES

RESEARCH FINDING MAINTENANCE NEEDS ANIMALS AND GROWTH From a large number of experiments it is how known how much total food and how much protein must be fed over and above the maintenance requirement to produce each pound of live weight increase in growing or fattening animals and each gallon of milk from the cow, states a report by Dr. I. E. Coop, professor of animal husbandry. Lincoln College, in a bulletin issued by the Canterbury Chamber of Commerce. The main foodstuffs of animals are of plant origin and it is of interest, therefore, to compare the composition of plants and animals. The following table gives average percentage compo; sitions of grass and of sheep.—

Carbohydrate is the name given to a class of substance of which sugar, starch, cellulose and fibre arc typical. They form the main constituents of plants but occur only to a very small extent in animals. Protein is another type of material. It varies fairly widely in plants but is one of the main constituents of animals, muscle being composed almost entirely of protein. Fat is a familiar substance occurring only in small amounts in plants but often reaching high proportions in animals. Minerals form the skeletal structure or bones of animals as well as occurring in small amounts in the other tissues. They also occur in small amounts in plants. The vitamins are substances which are required for growth of animals but in such small quantities that special methods of analysis are necessary to determine thenconcentrations. Wheras animals are composed, apart from water, mainly of protein and fat, grass is mainly carbohydrate with lesser amounts of protein. Animals are able to build UD fat from any of the constituents carbohydrates, protein or fat, but they are not able to build up body protein or muscle from anything except the protein in the food. Thus in the growing animal the food must be sufficient both in regard to the total food given and also in the total amount of protein contained in the food. ... , , When the food is eaten it is acten upon by the digestive juices in the stomach and intestines of the animal. The part which is digested is absorbed into the bloodstream and is utilised by the animal. That which is not digested is eliminated from the body in the. form of dung. Herein lies one of the biggest differences between foods, for the fraction left undigested is the biggest loss in their ultimate utilisation. Some foods such as young grass, milk, crushed grains, etc., are 80-90 per cent digestible, whereas in coarser foods such as hay and straw, less than 50 per cent of the food is digestible, the rest being of no. use to the animal. We refei to the digestibility of a food as the percentage which is actually digested and utilised by the animal. That portion of the fcod digested can now be used by the animal for. a number of purposes. First priority goes to supDlying the energy required to keep the heart beating and the brain functioning, to enable the animal to move about, to digest its food, and to keep itself warm. For these purposes not only is a minimum total amount of food value required but also a certain amount of nrot.e ; n is necessary for replacements and wear and tear of the muscle and other tissues. This is analogous to overhead costs, reoresenting food given for the sole nurpose of keeping the animal alive. The amount of food thus required for any animal is known as the maintenance requirement. _______________

Grass Sheep Water ..80 (iO Carbohydrate .. 13 1 Protein . .. 4 10 Fat .. . . .. 1 20 Minerals 2 3