MILK PRODUCTION 339 



tion: (a) in changing the proportion of water and total 

 solid matter; (6) in changing the relative proportions of 

 proteins, fat, and sugar, (c) in changing the constituents 

 of the fat. (2) Effect upon flavor. 



440. Effect of food on the proportion of milk solids. 

 In discussing the effect of food upon the proportion 

 of total solids, the question is, Can the richness of milk 

 be modified by changes in the ration? For instance, is 

 the milk from a very generous food-supply richer than that 

 from a moderate or scanty ration, or will a highly nitrog- 

 enous ration cause a secretion of milk with a higher per- 

 centage of solids than a ration poor in protein? It would 

 probably be generally conceded that if variations in milk 

 are caused in these ways, they are small as compared to 

 those due to breed characteristics or to individuality. 

 Can we bring about variations sufficiently large to be 

 important? This question has been much discussed and 

 much investigated from the work of Kuhn in 1868 down 

 to the present day. Many experiments have been con- 

 ducted for long periods and short periods in which very 

 moderate rations have been compared with very large 

 ones, highly nitrogenous foods with those of a low pro- 

 tein-content, dry with green or succulent materials, and 

 grains of the same class with one another, and, in a great 

 majority of cases, the verdict has been that no consist- 

 ent relation appears to exist between the quantity or 

 character of the ration and the proportion of solids in 

 the milk, a conclusion that has run counter to a very per- 

 sistent popular belief. In some cases, a temporary change 

 has appeared in the milk immediately after a violent change 

 in the ration, but in most instances of this kind, there was 

 very soon a return to the animal's normal product. In 

 a small proportion of experiments, the milk appeared to 



