New Ideas in Feeding

WK E HAVE had to revamp many of our old ideas about feeding livestock. War proved again the tremendous importance of food. Wc had to get all the milk, eggs, poultry, meat, pork, lard, beef, veal, lamb, and mutton we could and make every tittle of grain count in doing so. Chicken was compared with hog and hog with steer to see which yielded the most nutrients for humans in return for the least feed. Egg was measured against pork and pork against beef to determine relative food values. A dozen questions were raised that we thought we had answered pretty well before—the best weight at which to market swine, for example, and the amount of grain to feed to fattening steers. We discovered that an animal's increase in live weight or the total quantities of eggs and milk were not exact enough measures of relative efficiency in converting feedstuffs into foods for human use. We had to consider the separate nutrients, the vitamins, minerals, proteins, and energy values, because one animal product may represent a highly efficient production of protein, and another of fat. Besides, supplies of common feeds were often scant, and new types of feed and sometimes entirely new feeds or feed byproducts were introduced. Out of this situation came extensive changes in diets and rations for livestock. Some of them are transient reflections of the war, but many may be permanent. Early in the war, committees of the National Research Council undertook to state the nutritive requirements of diflfercnt classes of livestock on a basis comparable to those for humans. They used the best available information on all the known essential nutrients in arriving at the figures, which were set up as guideposts for the rationing of livestock and served as indices of the research requirements to confirm or modify our information on the exact needs for energy materials, proteins, mineral elements,