186 FIRST PRINCIPLES OF AGRICULTURE. 



The Period of Lactation is the time which elapses 

 between the birth of the calf and dryness, and varies 

 with different animals even of the same breed. During 

 this period the yield and composition of the milk vary. 

 The milk flow is greatest and the quality poorest in the 

 beginning ; as the period increases the flow gradually falls 

 off, and, as a rule, the quality improves, though the rate 

 of improvement is dependent somewhat upon food and 

 management. The fat globules are larger at the begin- 

 ning and smaller at the end of the period. 



Colostrum. A few days elapse after the birth of the 

 calf before the milk is fit for use. The product obtained 

 is called "colostrum," and is especially suited to the 

 needs of the young offspring. It differs from milk in 

 containing a much larger amount of solid matter and 

 ash, and in showing but little sugar. 



Milk Drawn at Different Times also differs in com- 

 position, though the influence of time of milking is not 

 the same for all animals. In some cases the morning's 

 milk will be greater in quantity and poorer in quality than 

 the evening's milk, while in others the reverse is the 

 case; hence the variation in the milk of a herd is not 

 so noticeable as that from, individual cows. 



It is also a matter of common observation that the milk 

 first drawn is poorer, particularly in fat, than the " strip- 

 pings," or that last drawn; frequently the " strippings," 

 or last pint drawn, contain six to eight times more fat 

 than the first pint, while the other constituents, albumi- 

 noids and sugar, are more evenly distributed ; this vari- 

 ation in composition, in connection with the fact that 

 the fat globules are larger in the " strippings " than in 



