Testing Milk on the Farm. 135 



the butter fat produced by the cow on certain days, but 

 5 neither gives a correct record of her actual average daily 

 ; performance for this lactation period. 

 I A sufficient number and variety of tests of the milk of 



many cows have been made to prove that there is no 

 ; definite regularity in the daily variations in the richness 

 of the milk of single cows. The only change in the 

 f quality of milk common to all cows is, as stated, the nat- 

 [ ural increase in fat content as the cows are drying off, 

 f and even in this case the improvement in the quality of 

 ; the milk sometimes does not occur until the milk yield 

 \ has dwindled down very materially. 



159. Causes of variations in fat content. The quality 

 of a cow's milk is as a rule decidedly influenced by the 

 following conditions: 



Length of interval between milkings. 



Change of feed. 



Change of milkers. 



Eapidity of milking. 



Eough treatment. 



Exposure to rain or bad weather. 



Unusual excitement or sickness. 



160. Disturbances like those enumerated frequently 

 increase the richness of the milk for one, and sometimes 

 for several milkings, but a decrease in quality follows 

 during the reaction or the gradual return to normal con- 

 ditions, and taken as a whole there is a considerable 

 falling off in the total production of milk and butter fat 

 by the cow, on account of the nervous excitement which 

 she has gone through. Aside from changes due to well- 

 definable causes like those given abve, the quality of 



