THE FEEDING OF MILCH CATTLE 325 



limit, and it is shown that from a certain stage the 

 quantity of food required to produce a given in- 

 crease of milk must be more and more, until finally 

 a point is reached where, in spite of large additions 

 to the ration, no extra milk is obtained. If the 

 milk yield be raised by the use of more food, it is 

 the last quart that requires the most nutriment 

 for its production. How far the yield of milk can 

 be raised cannot be stated beforehand, it can only 

 be found by direct observation. 



(c) The effect of food-protein on the production 

 of milk. 



As milk contains a lot of protein substances, 

 milch cattle must always have a sufficient quantity 

 of this material in the ration if the tissues of the body 

 are not to be used for the formation of milk. All the 

 investigations in which foods rich in protein have 

 been compared with those poor in this material 

 have shown the powerful influence which the former 

 exercise upon the yield of milk. If the allowance 

 of protein in a ration is diminished, then, although 

 there may be a sufficiency of non-nitrogenous 

 material, the quantity of milk decreases rapidly, as, 

 for instance, in one observed case from 97 kg. to 

 7-65 kg., or in another from 13-4 kg. to as little as 

 8-45 kg., the condition of the cows falling off at the 

 same time. As a rule, no influence of the food- 



