32 MAIXE STATE COLLEGE 



during the last few weeks a cow produces milk previous to the 

 time of parturition, the percentage of solids in the milk is greatly 

 increased. It is a question whether the somewhat uniform 

 increase that is seen to occur in the quantity of solids, is not due 

 to the corresponding decrease in the yield of milk. It would not 

 be strange if extended observations finally show that any cause 

 tending to largely augment the amount of milk produced within a 

 given time has in general the effect of diminishing the percentage of 

 milk solids, whether that cause be breed, food, season or any other. 

 For this reason it is not safe to measure the value of a ration for 

 either butter or cheese production by the increase or decrease 

 which such ration may cause in the yield of milk. 



A part of the animals have shown an increase in the relative 

 amount of fat in the milk solids as the period of lactation has 

 advanced, but this has not been generally true and seems there- 

 fore to be an individual matter. 



(•i.) Tlie daily variation of the composition of milk. 



There is a daily variation in the composition of milk which 

 seems to be independent of breed, individuality, food, or any 

 other known cause. "While the milk of any given animal may 

 have essentially the same composition during six days out of 

 seven, there occasionally comes a day when there is suddenly an 

 unexplainable change and which is sufficiently great to render it 

 entirely unsafe to judge of the effect of food by the composition of 

 a single day's milk. "When, however, we take the averages of 

 periods of four or five days each, we find that these averages com- 

 pare very closely. If, for instance, the milk of a single animal 

 were to be analyzed for every day in a month, and these analyses 

 were to be averaged in six periods of five days each, it would be 

 found that the six averages would give practically the same fig- 

 ures. Whatever permanent changes take place in the character of 

 the milk of the individual animal are periodical in their nature and 

 seem to be due largely to conditions over which we have no control. 

 "We must after all regard any particular cow as a machine set to a 

 certain gauge, which is capable of producing a certain kind of pro- 

 duct, and while we may make changes in food and surrouDdings 

 which increase or decrease the amount of product, we can do but 

 little in the way of changing its character. 



Composition of Skimmed Milk, Cream a>~d Butter Milk. 

 On the days that the whole milk has been analyzed samples of 



