176 THE CHEMISTRY OF CATTLE FEEDING 



This method, it is said, has given very satisfactory results 

 in practice when applied to a considerable number of animals 

 at once. The fundamental assumption, however, does not 

 hold for individuals ; or at least, the fluctuations due to other 

 disturbing factors do not permit of accurate and reliable 

 observations being made in this way in individual cases. The 

 two methods should be regarded as complementary ; each 

 forms a useful check upon any inferences that may be drawn 

 from the other. 



It was formerly supposed that the yield and composition 

 of the milk could be to a large extent controlled by the food. 

 More recent experiments tend to show that such is not the 

 case; and many people now believe that the food has very 

 little or no influence at all. 



A good deal, perhaps, depends upon the point of view from 

 which the subject is regarded. The natural capacity of cows 

 for the production of milk varies very widely; and no kind 

 or quantity of food that can be given will convert a bad milker 

 into a good one. On the other hand, a certain minimum 

 ration is indispensable for the maintenance of the animal and 

 production of the maximum yield possible under the conditions. 

 If the rations be reduced below this minimum, whatever it 

 may be, the yield of milk will be speedily diminished. 



Some cows, it is true, exhibit such a strong inherited 

 tendency to produce milk that they continue to yield large 

 quantities perhaps nearly the maximum even when the 

 rations are insufficient; but under these conditions the cow 

 is bound to lose weight. It is obvious, therefore, that the 

 process cannot be continued very long without reacting on 

 the yield. This conclusion is entirely confirmed by the 

 experience of practical dairymen who are accustomed to sum 

 up the matter in the phrase, " Feed your cow, and she will 

 feed you." Excessive amounts of food should, however, be 

 avoided ; not only on pecuniary grounds, but also because it 

 has been found that, when the rations are largely dispropor- 

 tionate to the yield of milk, the animal grows fat, the glands 

 become sluggish, and the yield is diminished. 



Probably no one now denies that the yield of milk may be 



