THE PRINCIPLES OF FEEDING.

Otago Witness, Issue 3511, 28 June 1921, Page 8

THE PRINCIPLES OF FEEDING.

The value of chemical analysis in making up rations in the Homeland is much appreciated ; so much so, indeed that fanners there have a Food Bill as well as a Fertiliser Bill, the percentage of the valuable constituents being given in a foodstuff the same as" is done in the Dominion in the case of an artificial fertiliser. In New Zealand, strange to say, farmers are in no way safeguarded in respect to the valuable ingredients or otherwise of the different foods, hut must just make a guess as to their feeding values. The whole subject is admittedly difficult, but of great interest if economy is to be the war cry for the next few years. Plants get those substances they require—oxygen, hydrogen, nitrogen, carbon, sulphur, phosphorus, potassium, calcium, magnesium, and iron—from the air or ground, and animals get them from the plants they eat. Fdods are divided into three main ela«xses—carbo-hydrates, fats, and protein. Carbo-hydrates is another name for starch or sugar. Starch is made up of three elements, the formula being C 6 HlO 05. Fat contains the same elements, but a larger proportion of carbon. Protein contains the same three elements, and in addition contains nitrogen and some of the other elements. Thus these three foods can supply all the elements needed by the body. Sugar or starch is used by the body to maintain its energy. They are burned to maintain heat. The body lias the power to change them into fat. Fat is also burned in the body to produce heat or energy. Protein is used to build up the cells and tissues of the body'. Little or none of it is burned. Experiments show that 11b of fat, when burned, produces 2.25 times as much energy .as lib of starch, hence we say that lib of it is equivalent to 2.25ib of starch as food for animals or man. People in cold countries need much more fat to keep them warm, while those in warm countries should eat more fruit and less fat. The composition of feeds is commonly given in terms of water, ash, protein, ether, extract, or fat, crude fibre, and nitrogen free extract, the last two making the carbo-hydrates. Water can be supplied in the drink, and need not be considered in determining the value of food. The ash is the mineral matter as found in sulphur, phosphorus, potash, calcium, magnesium, and iron, and is what is left after burning the food. Protein contains about 16 per cent, nitrogen, and is the most valuable as well as the most costly food. Ether is used to extract the fat, and hence this is called ether extract. The crude fibre is the cell or framework of the plant, and is of very little food value. The rest, called nitrogen free extract, is what is left, and is mostly sugar, starch, etc. Fat is worth 2.25 times as much as starch as a food. Take, for example, 1001 b of corn analysing 66.71 b of carbo-hydrates and 4.31 b of fat and 7.91 b of protein. We multiply the fat by 2.25 to find its equivalent in starch or carbo-hydrates. In this case we have 66.7 plus (4.3 x 2.25) equals 76.4. Therefore we say the fat and carbo-hydrates together equal 76.4 of carbo-hydrates. Next we divide the 76.4 of carbo-hydrates by the 7.Sib of protein, which gives 9.7 for a ratio. That is to say, we have 9.7 times as much carbo-hydrates arid fats combined as we have protein. This is called the nutritive ratio. So, if you fed corn alone, you would be feeding lib of protein for every 9.71 b or carbohydrates. But here is the trouble. It has been determined hv careful tests that the feeding standard for dairy cat-tie should be 1 to 5.4, so corn fed alone would ho a mistake, there is too much carbo-hydrate, and it would be but common sense to feed some foodstuff in addition with high content of protein, something in the nature of cotton seed or linseed meal. A combination of feeds, therefore, is necessary to secure the beet results in feeding stock of any kind, and this combination must be arranged with care. It must be remembered that foods with the same analysis may easily vary very considerably in food value, because the ordinary analysis is at best but a rough-and-ready attempt to measure the value of the foodstuff to the animal. The oil or fats will most probably vary in feeding value, according to tlie different plants or seeds from which they a»e obtained. It is probable that, the oil in linseed cakes is of greater feeding value than the oil in cereals and cereal by-products, hut an analysis makes no distinction between the different oils. Then the recently-discovered “accessory food factors” or “vitamines,” which are of great importance in the growth of young animals, arc as yet unrecognisable by chemical analysis. The feeding value

of a food, analysing very similarly to some other ' foodstuff, may be preferred owing to its better digestibility when fed with other foods to the same animal. An analysis can not take in account some important qualities in feeding stuffs. The chief of these are the palatability of the food, laxative effect, physiological effect, and the desirability of giving a certain variety to the diet. Although we have up to the present practically done little in demanding that foodstuffs put on the market should be analysed, and have indicated that a chemical analysis of a food may not be all that is satisfactory, yet a wise use of same has led, and will continue to lead, to greater economy and to much better results in the feeding of all classes of live stock. It comes to this: For commercial, purposes chemical analysis can safely be used to-compare different foods of the same class. It should, however, stop there, for reasons which we have briefly traversed in the loregoing survey. Chemical analysis cannot tell when a food will succeed. It can tell, however, when it must fail, as we know what materials are required to make up the general composition of farm animals.