FACTORS THAT AFFECT COMPOSITION OF MILK 45 



differences between the breeds. This is shown by the data in 

 the following table representing the milk from individual animals 

 in the different breeds. 



VARIATION IN PERCENTAGE OF FAT OF MILK OF INDIVIDUAL Cows 



Influence of age of cow on fat-content of milk (Wing). 1 



A notion is prevalent that the percentage of fat in the milk 

 is also affected by the age of the cow ; that during the first and 

 second periods of lactation the young cow usually gives milk 

 poorer in fat than when she is mature. During the years of 

 greater vigor the percentage of fat is supposed to be fairly 

 uniform ; but in cows of advanced age it may sometimes again 

 fall to a low point. Recently some records have been published 

 that go to show that the age of the cow has little, if any, influ- 

 ence on the percentage of fat in the milk. In the one case the 

 observations were made on a large number of cows of all ages, 

 for a week at a time, comparatively early in the period of lacta- 

 tion. In the other the observations were made on a single 

 herd extending over several years, and the percentages of fat 



1 Milk and Its Products. 



