FACTORS THAT AFFECT COMPOSITION OF MILK 43 



FACTORS WHICH INFLUENCE PERCENTAGE OF FAT AND SOLIDS 



IN MILK 



There is great variation in the percentage of fat in normal 

 milk. The average of large numbers of analyses, including 

 milk of the different breeds during the entire year, shows that 

 the average percentage of milk-fat in this country is not far 

 from 4 per cent. If individual herds are considered on a yearly 

 basis, the average may vary from approximately 3 per cent to 

 5 per cent or higher. Between different individual cows, the 

 average may vary even more. Many of the conditions that 

 affect the percentage of fat in milk are 'fairly well known, while 

 others are little understood. Some of the well-recognized con- 

 ditions that influence the fat content of milk will be consid- 

 ered. 

 Influence of breed (Van Slyke). l 



It is well known that the percentage of fat in milk varies in 

 a somewhat characteristic way with the kind of breed of cow. 

 While there is marked variation in individuals of the same breed, 

 there is found to be a fairly uniform difference, more or less 

 marked, if we consider the averages of several individuals. It is 

 largely owing to this influence that we find the milk of one coun- 

 try differing from that of another, or the milk of one section of a 

 country differing from that of another section. For example, 

 the average amount of fat in milk in Germany and Holland is 

 fully -J- per cent lower than in this country, because the prevail- 

 ing breeds of cows there are those producing milk comparatively 

 low in fat. The following figures, taken from the records of the 

 New York (Geneva) Agricultural Experiment Station, repre- 

 sent averages of many individuals for several periods of lacta- 

 tion: 



1 Loo. cit. 



