50 CLEAN MILK 



Thus in the months of November, December and January, the solids 

 may average 13.36 per cent, and the fat, 4.16 per cent.; while in 

 May, June and July the solids may average 12.68 per cent, and the 

 fat 3.82 per cent. 



The changes in the composition of one cow's milk are great 

 and may be brought about through various influences, as, for 

 instance, fright, excitement, rough handling, change of milker, 

 exposure to bad weather, unfamiliar surroundings, sudden change 

 in the character of food, and irregularity in time of milking. It 

 follows without saying that all these unfavorable influences are, as 

 far as possible, to be avoided. 



In an analysis of hundreds of samples of milk from single cows, 

 Farrington found that in the case of a Holstein there was as much 

 difference between the highest and lowest percentage of fat as be- 

 tween 6.6 per cent, and 1.5 per cent., while in the case of the Jersey 

 — in which sudden changes are most common — the highest was 12.3 

 per cent, of fat; the lowest, 2.9 of fat. The variations in the per- 

 centage of the other solids — proteids, milk sugar and salts — are 

 very slight, especially of milk sugar. 



The mixed milk of a large herd is pretty constant in composi- 

 tion except as influenced by the season and by the times the cows 

 calve. For the composition of milk varies at different times in the 

 milking period. The milking period of the cow lasts about 323 days 

 on the average after calving, she going dry about eight weeks 

 before she calves again. The interval between two calving days 

 averages about 398 days. 



In cows which are well tended and fed the percentage of fat 

 increases as the milking period progresses, so that the milk is richer 

 at the close than at the beginning of the period of milking. 



The period of heat in a cow is often accompanied by a 

 diminished yield of milk which is poor in fat (so that the fat may 

 be reduced to one per cent.), and the milk curdles on boiling. The 

 fat after this period is, however, proportionately increased over that 



