FORTY-SECOND ANNUAL CONVENTION 33 



These figures give a general idea of the differences existing 

 in the average compositk)'n of the milk of the dairy breeds. 

 Analysies of the milk of tlie various breeds indicates that the 

 albumin content does not seeni to vary with breed, but that the 

 casein is highest in milk rich in butterfat. The various breeds 

 of dairy cattle have been bred for years with certain purposes 

 in mind until now if one desires quantity of milk at the expense 

 of solids or vice versa he may know which breed to choose, 

 having in mind the fact that there are certain families and 

 individuals of each breed which produce milk differing markedly 

 in composition from the average for the breed. 



The second point that I propose to mention is tlie variation 

 in the composition of milk due to lactation. The milk from all 

 cows does not show'the same variations due to the effect of lacta- 

 tion since much depends upon the individuality of the cow and 

 the condition she is in. Data which has been tabulated shows 

 that as a rule the percent of solids in milk are higher at the be- 

 ginning and at the end of lactation than during the intervening 

 period. 



Bearing in mind that the average composition of milk 

 varies with different breeds, as well as with individuals of the 

 breed, and with the stage of lactation, let us consider feed as a 

 factor in causing variation in the composition of milk. At one 

 time it was generally believed that the constituents in the feeds 

 eaten by cows were With little change secreted into the milk, 

 and this led to the belief that the fat content of milk could be 

 made to vary by changing the nature of the feeds. Some interest 

 was aroused in this idea by Kuhn, a German investigator, who 

 fed palmnut cake meal in the ration of three milch cows and 

 obtained data which seemed to indicate that the fat content of 

 the milk was appreciably raised. This, together with the fact 

 that many farmers believed that the fat content of milk could be 

 made to vary with certain combinations of feeds, has led to the 

 accumulation of a vast amount of data on the subject. Unfortu- 

 nately, a considerable amount of evidence was based upon data 

 taken from brief feeding periods or from individual cows which 

 experienced a variation in the composition of their milk not 



