116 MILK 



THE VARIATION OF MILK CONSTITUENTS DURING THE LACTATION PERIOD IN FOUR- 

 WEEK PERIODS 



On the basis of these figures, the quantitative variation in milk 

 constituents is, briefly, as follows: 



Total Protein. — The total protein begins high right after the 

 colostrum period, and diminishes for from four to six weeks. The 

 lowest point is then maintained up to about the eighth month of 

 the lactation period, and the percentage then rises. The rise is 

 rapid toward the end of lactation. 



There is a wide range of variation in the total protein during 

 the lactation period; the variation on the basis of four-weekly 

 figures is greater than that of fat. The daily fiuctuations of fat, 

 however, are always greater than those of protein. 



In colostrum there is an abnormal amount of albumin and, 

 therefore, the total protein is also great. The percentage then 

 decreases rapidly up to a point when the decrease ceases. From 

 this time on the increase is slight, but about two months before 

 the close of lactation the increase is marked. 



Eckles and Shaw think that the decUne of protein after the 

 colostrum period can be explained by assuming that the cow 

 accumulates considerable of body substance during pregnancy 

 and that part of this body fat is converted into milk protein, and 

 "after calving she does not consume sufficient food to furnish 

 maintenance and support milk production." 



If the amount of protein in milk during the first four-weekly 

 period of lactation is placed at 100, the relation of the other pe- 

 riods becomes manifest. The successive figures are these: 100, 94, 

 94, 96, 100, 100, 102, 102, 110, 118, 120, 125, 133. The initial 

 decline, the constancy for four months, and the final increase are 

 clearly expressed in these figures. 



Casein.— The variation of casein is similar to that of total 

 protein. If the amount of casein in the milk during the first 

 period is placed at 100, the relation of the amounts in the later 

 periods compares as 100 to 88, 93, 93, 100, 100, 102, 107, 114, 119, 



