GENERAL PROBLEMS IN DAIRY HUSBANDRY 351 



years. Then the cows were returned to their owner and fed by him as 

 before. During the time the cows were at the Station they gave 42 

 per ct. more milk and 51 per ct. more fat than when with the farmer, 

 due to the better feed and care they received. 



559. Influence of feed on richness of milk. Until recent years it was 

 believed that milk varied in percentage of fat from milking to milk- 

 ing, according to the daily feed and care the cow received. We now 

 know that if the cow receives sufficient nutrients to maintain her body 

 weight, the percentage of fat can not be materially altered for any long 

 period of time by greater or less liberality of feeding or by supplying 

 any particular kind of feed. Cows starved or greatly underfed may 

 produce milk somewhat lower in fat percentage than normal. Some feeds, 

 as cocoanut meal, for example, apparently often cause a slight increase in 

 the fat percentage of the milk, which may be more or less temporary. 



Statements have often been made that certain feeds stimulate the pro- 

 duction of milk and of fat to an extent not explained by the amounts of 

 nutrients they supply. However, the results of the trials which have 

 been carried on to study this matter disagree. A certain feed has been 

 said in some instances to stimulate milk or fat production, and in other 

 cases the same feed has had an unfavorable effect. In most such trials 

 the experimental periods have been too short to warrant definite con- 

 clusions. Up to the present there is no very positive evidence of any 

 continued specific effect of a feed in stimulating milk production or in- 

 creasing the percentage of fat. 



The Jersey cow gives milk which is relatively rich in fat, and the Hoi- 

 stein, milk that is relatively low in fat. No kind of feed or care will 

 cause the Jersey to give milk like that of the Holstein, or the reverse. 

 Were a piece of skin, clothed with yellow hair, taken from the body of a 

 Jersey cow and grafted on the body of a Holstein cow, we should expect 

 the grafted portion to continue growing yellow, Jersey-like hair. In the 

 same way, were it possible to graft the udder of a Jersey cow on to the 

 body of a Holstein, we would then expect the Holstein to give Jersey-like 

 milk. It is not the body of the cow or the digestive tract, but the glands 

 of the udder which determine the characteristics of the milk yielded by 

 each individual cow. This is what we should expect, for if milk varied 

 with every slight change of food and condition, the life of the young, 

 dependent on such milk, would always be in jeopardy. 



560. Can the yield of milk or fat be increased by feeding fat? Numer- 

 ous experiments have been conducted in this country and in Eu- 

 rope to determine the effect on the yield and fat content of the 

 milk when various fats are added to the ration. After feeding 

 cottonseed-, palm-, corn-, cocoanut-, and oleo-oil, and stearin, the 

 solid fat from beef, to cows, Woods at the New Hampshire Station 30 

 concluded that the first effect of such feeding is to increase the percentage 

 of fat in the milk, but with the continuance of such feeding the milk 



"N. H. Bui. 20. 



