230 



PRODUCTIVE FEEDING OF FARM ANIMALS 



conducted at the different stations differed more or less, as did also 

 the breeds represented in the respective trials. The results, there- 

 fore, cannot be taken as absolute evidence of the capacity of the dif- 

 ferent breeds for dairy production, but they doubtless show in a 

 general way the relative value of the breeds in the dairy. We note 

 that the breeds rank as shown below in regard to: (a) Yield of 

 milk, (b) yield of butter fat, (c) per cent of fat, (d) feed cost for 

 100 pounds milk, (e) feed cost per one pound butter fat. 



Individuality. There are wide variations between individuals 

 within the same breed as to the capacity for milk production and 

 the. quality of the milk produced. These variations are of much 

 greater magnitude than the average differences between the breed. 

 The great difference between individuals of the same breed as re- 

 gards the amount of production is familiar to all ; an average cow 

 produces, say, 20 pounds of milk a day, containing three-fourths 

 pound butter fat; a very good dairy cow, on the other hand, will 

 yield over twice this amount, and exceptional producers will give 

 more than quadruple the figures stated. But the average quality 

 of milk of cows of the same breeds also differs greatly. The 

 variations are probably larger within the Jersey and Guernsey 

 breeds than in any other breed; there are thus cows or families 

 within these breeds that produce milk of an average fat content 

 above 6 per cent during the entire lactation period, while individuals 

 of other families will generally not go over 4 per cent. In the 

 same way, we find some Holstein cows producing milk with over 

 4 per cent fat, and others whose milk will contain less than 2.8 per 

 cent, on the average, for a considerable period of time. 



Age of Cows. This is not, on the whole, an important factor. 

 As a general rule, heifers and young cows will give milk of a some- 

 what higher fat content than older cows, but the differences in the 

 average quality of the milk for a long period of time, say one year, 

 are only within a few tenths of one per cent in the fat content, and 

 there are some individuals whose milk changes with advancing age 

 in the opposite direction from that stated. 



