FACTORS THAT AFFECT COMPOSITION OF MILK 53 



there is a great difference in cows in this respect, some being 

 very sensitive, while others are scarcely affected at all. In 

 our experiments cows that have been giving milk for a long time 

 have been less sensitive in this respect than fresh cows that were 

 giving a large quantity of milk, but this may have been due to 

 individual characteristics of the animals tested and not to the 

 advanced period of lactation. I would recommend, therefore, 

 in order to obtain the best results from any cow that first of all 

 she be treated kindly, all sources of excitement being avoided 

 so far as possible. She should also be fed and milked at regular 

 intervals, by the same person, and all conditions should be 

 maintained as nearly uniform as possible at all times. It is 

 my opinion that kind treatment and pleasant surroundings will 

 have a greater influence upon the quality of milk than the kind 

 of food, provided that the ration given contains sufficient nutri- 

 ment for the maintenance of the animal." 

 Influence of drouth on composition of milk. 



In a study of the milk of fifty herds of cows, Van Slyke found 

 that the chemical composition was affected by a drouth during 

 the summer months. The constituent most affected was the 

 casein, which decreased both in actual percentage and also in 

 relation to the fat. The extent of this variation is shown in the 

 following table : 



Table Showing Variation of Fat and Casein as 

 Summer Drouth — Van Slyke 1 



Affected by 



Month 



Pounds of Fat in 



100 Pounds of 



Milk 



Pounds of Casein 



in 100 Pounds of 



Milk 



Pounds of Casein 

 for One Pound 

 of Fat in Milk 



May ...... 



June 



July 



August 



September .... 

 October 



3.58 

 3.59 

 3.71 

 4.04 

 3.97 

 4.20 



2.40 

 2.33 

 2.20 

 2.26 

 2.47 

 2.69 



0.67 

 0.65 

 0.59 

 0.56 

 0.62 

 0.64 



1 Geneva, Bui. 105, N. S., p. 132. 



