What to Feed a Cow

by R. E. HODGSON and W. L. SWEETMAN

THE GOOD dairyman knows that the difference between just any feed and good feed is profit—that his cows produce milk efficiently only when their ration gives them enough of all the nutrients they need. Just filling their stomachs is not enough.

Cows use nearly half their feed to maintain body weight, repair worn tissues, and get energy for all vital processes. The rest is used for production. During the cycle of lactation-reproduction, the cow needs feed to produce milk; to grow, if she is immature; to develop the fetus, if she is pregnant; and to lay on fat. The important point is that good dairy cows use more nutrients for making milk than for other production purposes, and must be adequately fed if they are to produce as much as their inheritance permits.

Several standards giving the amounts of protein and total digestible nutrients have been proposed as guides to feeders. One of them, drawn up by the Committee on Animal Nutrition of the National Research Council, gives a list of recommended allowances, which is reproduced in table 1 as a guide for the feeder. Cows fed the suggested rations, including roughage of high quality and concentrates that provide the various needed substances, thrive and produce well. But feeding at even higher levels, particularly total digestible nutrients from which energy is derived, may result in greater production. Many farmers have found that under certain economic conditions such a practice is profitable. Lack of energy-giving feeds limits production oftener than any other deficiency. The only way to correct it is to provide enough feed.

Of course other nutrients may be lacking. In some areas, like the Great Lakes region and the Pacific Northwest, soils and water may contain too little iodine, and iodized salt or some other form of iodine must supplement the regular ration. Phosphorus, cobalt, and possibly iron and copper may be insufficient in several regions; special precautions must then be taken to provide the elements, either by adding them to the soil as fertilizers or feeding them directly as mineral supplements. Wheat, wheat millfeed, and oilseed byproducts included in the concentrate mixture will provide phosphorus. A farmer who suspects such mineral deficiencies in his animals should seek the advice of his State college dairy specialist. Cows fed roughage of poor quality a long time may not get enough vitamin A, and therefore may be subject to night blindness and diarrhea, and fail to drop normal calves. Vitamin A deficiency can be avoided by feeding good green roughages high in carotene.

1. Dairy cows need a well-balanced diet for growth, maintenance, to develop the fetus when pregnant, and to give milk. Here are recommended feed allowances. 1 Thiamine, riboflavin, niacin, pyridoxine, pantothenic acid, and vitamin K are synthesized by bacteria in the rumen and it appears that adequate amounts of these vitamins are furnished by a combination of rumen synthesis and natural feedstuffs. Manganese, iron, copper, and cobalt are clearly essential, but the amounts needed are not known. For growth, 0.6 gram magnesium is needed per 100 pounds of body weight.

2. Calves should receive colostrum the first few days after birth as a source of vitamin A and other essential factors.

3. While vitamin D is known to be required, data are inadequate to warrant specific figures for older growing animals and for maintenance, reproduction, and lactation.

4. When calculating the allowances for lactating heifers that are still growing, it is recommended that the figure for growth rather than maintenance be used.

5. When adequate amounts of vitamins A and D are fed for normal reproduction, extra amounts will probably not stimulate milk production but will increase the vitamin content of the milk.

Meeting Feed Requirements

Pasture and harvested roughages are highly important. They furnish the biggest part of the nutrients for the dairy herd, and are the cheapest source of feed. They supply specific needs like calcium, other mineral elements, and carotene. They are soil-conserving crops: The wise dairy farmer, then, is essentially a "grassland farmer," and his crop rotations, while favoring perennial forage, also include corn for silage and small grains that have the double value of being nurse crops for new seedings and providing energy-rich concentrate feeds to supplement the roughage.

Under most conditions we recommend that a farmer keep only as many animal units as the land he has available for pasture and harvested forage will adequately support. Only in special areas where market conditions permit-as in the fluid milk regions of the Northeast-is it ordinarily profitable to depend on purchased hay and concentrates. In planning the cropping program and the size of the herd that a farm will support, it is helpful to know what are the yearly feed requirements of cows. In table 2 we give examples of feeds and acres needed for a year by cows of different sizes and producing ability. The requirements are based on average conditions, including a pasture season of 6 months. They have worked out satisfactorily in many areas. The acre yield of the various feeds, of course, will vary with factors such as soil fertility and climate. Young stock require from about one-half to three-fourths as much feed and pasture as do milking cows.