In addition to the, requirements for mainte nance of tissues and for energy the body re quires a supply of water daily, in order to keep up the water content of the body and to provide a medium for the transfer of the food material from different parts of the body to other parts and for the elimination of waste matter.
How the Food Fulfills These Require Like the body, the common coarse feeds, grains, meals and fecdstuffs in general used for animals are made up of the following groups of constituents: Water Ash Protein (nitrogenous) Dry matter Carbohydrates (fiber, Nutrients nitrogen-f ree extract) Fats The use of the water in the food has already been indicated.
The Ash required by the animal does not need to be computed carefully because all the ordinary feeds furnish it in sufficient amount, provided a good variety is given and plenty of salt is supplied. Corn is slightly deficient in ash, but in the ordinary ration the feeds fed with corn make up for this deficiency.
Protein, carbohydrates and fats in food are commonly spoken of as the nutrients of the dry matter, since it is from those groups of con stituents that animals derive the matter and energy necessary for the uses already enumer ated. The protein is used to keep up the pro tein of the body — that is to replace worn-out tissues, to build up new tissues, ,for growth of hair, hoofs, horns and the like. A very import ant fact in this connection is that any protein in the ration in excess of that required for keeping up the nitrogenous tissues of the body can be used by any animal for the production of heat and energy. On the other hand, while protein can be used thus for the production ut heat and energy, thus serving the purpose of carbohydrates and fat, protein cannot be pro duced from the carbohydrates or the fats of feeds. Therefore it is always necessary to have a sufficient amount of protein in the ra tion. The discussion of the necessary amount of protein for different uses will be taken up later under various rations given.
The amount of digestible protein in feeds varies within somewhat wide limits. The per centage varies from 0.8 of 1 per cent in succu lent feeds, such as mange's, through 7.6 per
cent for red clover hay and 8.5 per cent among the cereals, to as high as 37 per cent for cotton seed meal. Thus it is seen that there is a large list from which to choose in regulating the amount of protein in a ration.
The Carbohydrates are divided by the chemists into what are called "crude fibre" and "nitrogen-free extract," because the crude fibre is less digestible than the other carbohydrate material. In a feed analysis, ash protein, fat and fibre are first determined. 'their sum is then subtracted from the total dry matter, and the result is called "nitrogen-free This term includes all the carbohydrates except the fibre. The digestible nitrogen-free extract and the digestible fibre have the same food value for all practical purposes and perform the same work in the nutrition of the animal. This work consists mainly in furnishing energy for whatever need the animal may have. If there is more energy provided in the ration than is needed at that particular time, the excess energy may be stored in the body as fat.
The amount of fibre and nitrogen-free ex tract in feeds, taken together, varies as much as does the protein, but there is always a rela tively larger amount of carbohydrates than of protein. In every case, when there is a low percentage of protein there is a high percentage of carbohydrates.
The Food Fats are used by the animal in about the same way as are the carbohydrates. They provide energy to be used in any way that the animal needs, and if the animal has more energy than is needed, it may he stored in the form of fat. The fat, however, has an energy value equal to about two and one-fourth times the energy value of the same weight of carbohydrates.
The amount of digestible fat in the different feeds varies without respect to the other con stituents. It is low in the coarse fodders, run ning up to 11.6 per cent in distillers' dried grains.
Factors in an Ideal In actually computing a ration for a given purpose there are six factors that should be considered: 1. Amount of food.
2. Digestibility of the ration.