MILK PRODUCTION 341 



understand the general failure to find a recipe for feed- 

 ing fat into milk. Experimenters who have added large 

 quantities of fat or oil to a ration have in all but a very 

 few instances failed to permanently, or even tempora- 

 rily, increase the percentage of fat in the milk solids; 

 and, on the other hand, rations rich in protein do not 

 appear to cause a larger relative amount of proteins in 

 the milk-dry substance than rations with a wide nutri- 

 tive ratio. As a matter of fact, after years of investiga- 

 tion and intelligent observation, we are not able to affirm 

 that the proportion of fat to other milk solids is in any 

 way related to the feeding of the cow, and if apparent 

 exceptions to the general experience have been noticed, 

 no one has discovered any general method or law whereby 

 the exception may be made the rule. 



Physiological disturbances may result from feeding a 

 ration so selected or treated that it is greatly deficient 

 in certain nutrients. In experiments by Jordan, Hart, 

 and Patten, the deficiency of phosphorus compoimds 

 in the rations of milch cows appeared to cause, among 

 other effects, a marked diminution of the proportion of 

 fats in the milk solids. By-product feeding-stuffs simi- 

 larly deficient might cause a similar result. 



442. Influence of food on the mUk-fats. — It should 

 not be inferred from the previous statements that none 

 of the compounds of the food enter the milk as such, or 

 that the qualities of the milk are in no way influenced 

 by the character of the ration. Such conclusions would 

 not be consistent with the outcome of numerous investiga- 

 tions. While it has become quite evident that the com- 

 position of butter, and therefore its qualities, such as 

 hardness and melting-point, are sometimes materially 

 modified by the cow's food, it is not now possible to state 



