Concentrates.—The common concentrates used on American dairy farms are cereals and mill-refuse feeds, starch or glucose refuse feeds, brewers' and distillers' feeds, and oil meals, especially linseed meal and cotton-seed meal. The amounts of these feeds that can be fed to dairy cows with profit will depend upon the price of the feeds, the production of the cows, and the prices obtained for the dairy products. In general, the carbohydrates of feed rations are supplied by farm-grown crops, while nitrogenous feeds are largely purchased, except when leguminous crops are grown. By the culture of creps of the latter class the amount of protein feeds that it will be necessary to purchase will be reduced to a minimum. Wheat bran may be partially replaced, nearly ton for ton, by carefully-cured alfalfa hay, or by five to six tons of pea

vine silage. Roughly speaking, the cereals may be considered of equal feeding value for dairy cows, and of similar value to bran or shorts, in rations as ordinarily fed. Cotton-seed meal, gluten meal, and linseed meal likewise possess nearly equal value, with the first two feeds occasionally ahead. The comparative value of feeding stuffs depends, however, to a large extent on the combination in which they are fed, a starchy feed being of greater value to a farmer having a good supply of protein feeds than to one who has mainly starchy feeds to select from. The feed-unit system furnishes a convenient and very satisfactory method of comparing the value of different kinds of feeds for dairy cows (p. 79).

The quantities of grain feeds fed by American dairy farmers vary considerably, from a few pounds to fifteen or more pounds

per head daily (Figs. 51 and 52). Only exceptionally large producers will give good returns for more than six or eight pounds of grain feed daily, with abundant roughage of good quality at hand. A common rule is to feed as many pounds of grain feeds a day per head as the cows produce pounds of butter fat during the week, and to feed as much roughage in addition as they will eat up clean. Another rule is to feed a pound of grain feed for every 3 to 5 pounds

of milk yielded by the cows, according to the character of the roughage fed, the quality of the milk, and the intensity of the system of feeding practiced (see also p. 77).

Mineral Requirements. Investigations at the Ohio Station have shown that good dairy cows, while not on pasture, are unable to maintain mineral balances during the time of heavy production, and draw on their body reserves, especially for the amounts of calcium, magnesium, and phosphorus necessary for the elaboration of the milk. Such a deficiency may have far-reaching results, both as regards the milk flow during the balance of the lactation period, the cows and their offspring. The best method of supplying the minerals required is to grow cattle largely on leguminous roughage or on pastures containing an abundance of legumes, and to feed the milch cows legumes through the entire year, if possible, including the dry period. If legume hay is not available, an allowance of about two ounces of bone flour per head daily, may be given mixed with the grain, or the cows may be given free access to the bone meal.21

Rations for Dairy Cows.-It is important, in making up rations for dairy cows, as for other classes of farm animals, to see to it that a liberal amount of easily digestible substances is sup

Fig. 52.–Weighing rations for the dairy herd. The cows receive seven pounds of grain for

each pound of butter fat produced. (Wisconsin Station.)

plied; nearly one-half of the dry matter of the ration should be given in the form of concentrated feeds in case of milch cows, the amount fed being governed primarily by the production of the cows. No moldy or decayed feeds should be fed, and, in the case of wet feeds, particular attention must be given to keeping clean the mangers and the premises about the stable. A variety of feeds is generally fed, often as many as half a dozen different ones, so as to stimulate the appetites of the cows. The modern dairy cow is a product of special-purpose breeding and high feeding, and, unless special pains are taken to cater to her wants, she will not be able to reach and maintain the high standard of production which may be reasonably expected of her (Figs. 53, 54, 55, and 56).

The following rations for milch cows are given as samples of the system of feeding adapted to the conditions in different sections of our country:

a Ohio Bulletins 295, 308, 330; Jr. Biol. Chem: XL (1919), p. 1 and 469.

FIG. 54.-Murne Cowan, 19597, Guernsey record cow for production of butter fat for one year: 24008.0 lbs. milk; 1098.18 lbs. butter fat; average test 4.58%.

Fig. 55.-Countess Prue, No. 43785, holds the record for the highest production of butter fat by a Guernsey cow for one year (1920), viz., 1103.28 pounds butter fat from 18,626.9

pounds milk; average test, 5.92%.

FIG. 56.-Duchess Skylark Ormsby, 124514, Holstein record cow for production of butter

fat for one year; 27761.7 lbs. milk; 1205.09 lbs. butter fat; average test, 4.34 per cent.