No. 4.] 



MILK SUPPLY OF CITIES. 



75 



What causes Variations in the Quality of Mill? 



In leaving this point, let ns briefly consider what causes 

 variations in the quality of milk, and summarize the scien- 

 tific work of our experiment stations and others up to date. 

 The mixed milk of mixed cows, as stated, is quite uniform 

 in quality. Mr. Clemence of the Board and the Dairy 

 Bureau has tested the mixed milk of his herd of common 

 cows with the Babcock tester every few weeks for nearly 

 two years, and has found a fat variation of only about .3 of 

 1 per cent.* But the milk of individual cows is constantly 

 varying from day to day, and the range is more than in Mr. 

 Clemence's case ; but it is usually less than 1 per cent, always 

 returning, however, in a day or two, to the average. But, 

 if the milk of one cow were mixed with that of other cows, 

 these sharp differences would be toned down and the milk 

 would be of more uniform quality. The cause of some of 

 these changes is unknown, and opens a field for interesting 

 and valuable work by experiment stations. 



Cows fresh in milk give poorer milk than do strippers, 

 hence, to have milk of as even quality as possible, there 

 should not be too large a proportion of new milch cows at 

 any time. 



Breed has much influence on the quality of milk, some 

 breeds averao-ino- richer than others. But skilful breeders 

 have developed rich milkers in the breeds which usually 

 give poorer milk, and have often got good dairy families 

 from the so-called beef breeds. On the other hand, negli- 

 gent breeding, or what is as bad, breeding for mere quan- 

 tity, will develop animals in the richest dairy breeds which 

 will give low-grade milk. 



Careful feeding of animals through several generations is 

 one of the influences that tend toward the development of 



* Recent complete chemical analyses resulted as follows : — 



