276 Agricultural Chemistry. 



of milk may be considerably reduced. This is evidenced by the 

 results secured at the Cornell Station with a poorly fed herd and 

 again when the same herd was liberally fed. Under those con- 

 ditions, where a liberal supply of nutrients was given, the flow 

 of milk was nearly doubled and the percentage of fat slightly 

 increased. Again, there appears to be some distinct evidence 

 that a change from a ration with a wide nutritive ratio to one 

 with a narrow ratio, is for a time, attended with a production 

 of milk slightly richer in fat ; but the change is only transient, 

 and even if the food with a high protein ration be continued, the 

 milk, after allowance is made for the effect of advancing lacta- 

 tion, shows a tendency to return to its previous composition. 



In any case, it appears that, provided cows are sufficiently fed, 

 change of feed has very little permanent effect upon the com- 

 position of their milk. Violent and sudden changes in the char- 

 acter of their feed may cause a sudden fluctuation in the com- 

 position of the milk, but after a short period it will tend to re- 

 turn to a composition characteristic for that animal. 



The opinion that it is possible to feed fat into milk has widely 

 prevailed, but such a notion is based upon a misconception o 

 how milk is formed. When, however, we remember that the 

 cells of the mammary gland are selective in function, and that 

 with the same feeds a Jersey cow always makes Jersey milk, and 

 a Holstein cow Holstein milk, then the many failures to feed fat 

 into milk become intelligible. The careful and well planned 

 work of Lindsey, in which a number of vegetable oils have been 

 added to a basal ration, gave in some cases slight but only tem- 

 porary increases of fat in the milk, while with other oils no 

 increase whatever was noticed. 



Certain feeds, however, affect the character of the fat in the 

 milk, which is manifested by a change in the hardness and phys- 

 ical properties of the butter produced. It is agreed that cotton 

 seed meal has the effect of raising the melting point of butter 

 while gluten feed, rich in oil, produces a softer butter of lowe 

 melting point. In experiments at the Wisconsin Station, Ion 



i 



