144 Testing Milk and Its Products. 



result would show the butter fat produced by the cow on 

 certain days, but neither gives a correct record of her 

 actual average daily performance for this lactation 

 period. 



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 quality of milk common to all cows is, as stated, 

 the natural increase in fat content as the cows are dry- 

 ing off, 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. 



163. Causes of variations in fat content. The qual- 

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

 the following conditions: 



Length of interval between milkings. 



Change cf feed. 



Change of milkers. 



Rapidity of milking. 



Exposure to rain or bad weather. 



Rough treatment. 



Unusual excitement or sickness. 



164. Disturbances like those enumerated frequently 

 increase the richness of the milk for one, and some- 

 times for several milkings, but a decrease in quality fol- 

 lows during the gradual return to normal conditions, 

 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- 



