Feeding Poultry

by H. R. BIRD

HALF a poultryman's expenses go for feed. More than half his worry and moil go into it. When feedstuffs are scarce, he must use them more efficiently. When they are expensive, their formulas might be changed, and he is not sure of their value. One of his main problems always is how to provide enough protein.

From studies at Beltsville of the protein needs of growing chickens, we found that the birds make their greatest gains, in proportion to feed consumed, when their ration contains about 21 percent protein. A diet containing much more or less than that is definitely less efficient. But when the birds are full-grown, the proportion of protein may be reduced, with satisfactory results, to about 16 percent for laying stock, and to as little as 13 percent in a maintenance ration for male chickens. Feed-consumption records of experimental birds show that chickens generally need more pounds of feed per pound of gain as they grow.

The war meant shorter supplies of high-quality protein supplements of animal origin. We found, however, that in well-balanced diets proteins of vegetable origin may constitute up to about 80 percent of the total proteins for chickens that produce hatching eggs, and 90 percent of the total for other mature chickens and for growing chickens and turkeys. Successful growing diets in which all of the protein is of vegetable origin have been devised for turkeys more than 8 weeks old that have access to good range. These percentages are a good bit higher than were once considered practicable. Because vegetable proteins are generally cheaper than those of animal origin, this knowledge bears directly on economy of production. Properly cooked soybean meal is an excellent feed for poultry.

Considerable progress has been made at the California Agricultural Experiment Station in expressing the protein requirements of growing chicks in terms of amino acids, which constitute proteins. More information on this vital subject and on the distribution of amino acids in feeds will help us to predict the feeding value of feedstuffs and feed mixtures from the results of chemical analyses. It is too much to expect, however, that the value of the usual protein supplements will be predictable entirely on the basis of their amino acid content, because they also contain vitamins that poultry need. The amino acids and vitamins, furthermore, do not exert their effects independently, but are interrelated. For example, work at the Wisconsin and Maryland experiment stations reveals that when growing chicks consume relatively large quantities of corn or gelatin, they have increased requirements either for tryptophane, an amino acid, or for nicotinic acid, a vitamin.

Also, we have discovered that for growing chicks a practical diet containing soybean meal as the only protein supplement is effectively supplemented either by an amino acid named methionine or by two vitamins : pantothenic acid and choline. It is also interesting to note that such diets are effectively supplemented by 2 to 4 percent of fish meal, which does not supply enough methionine, choline, or pantothenic acid to account for such an effect. The ability of these chemically dissimilar materials to substitute for one another probably is due to their role as intermediaries in metabolism, rather than as constituents of body tissues.

Research at the Wisconsin, New York, and Ohio experiment stations has yielded much valuable information about the need for the B-complex vitamins by different classes of poultry. The information has been useful as a basis for experiments on the utilization of byproducts, such as those of the fermentation industries, and of synthetic vitamins, to obtain nutrients formerly supplied by animal products.

As a result of research it is now possible to recommend quantitative allowances of the following nutrients for growing chickens. Six amino acids : Glycine, arginine, methionine, cystine, lysine, and tryptophane. Ten vitamins:A, D, K, thiamine, riboflavin, pantothenic acid, nicotinic acid, pyridoxin, biotin, and choline. And nine mineral elements : Calcium, phosphorus, sodium, manganese, iodine, potassium, magnesium, iron, and copper.