Specific Gravity of Milk 19 



in four or five days after calving, the milk loses its 

 colostrum character and takes on its normal condi- 

 tion. This change is a gradual and progressive one, 

 and is more or less dependent upon the physical 

 condition of the animal. When the cow is feverish, 

 or when there is local inflammation in the udder, 

 the colostrum character of the milk is retained 

 for a longer period than otherwise. The amount 

 of coloring matter present is also considerably 

 greater in colostrum than in normal milk, and the 

 percentage of fat varies very widely. Usually the 

 percentage of fat is less in the colostrum than in 

 the normal milk from the same cow, although oc- 

 casions are not infrequent where more fat is found 

 in the milk immediately after calving than at any 

 other time in the whole period of lactation. 



Specific gravity of milk. Some of the solids of 

 milk are heavier than water and some of them lighter, 

 milk as a whole having a specific gravity somewhat 

 greater than water. The variation in the specific 

 gravity is considerable, the range usually given being 

 from 1.029 to 1.035 at 60 F., the average being 

 about 1.032. In general, the effect of an increase 

 in the solids of the milk is to increase its specific 

 gravity, though .in milk extremely rich in fats (6 

 per cent or above) the specific gravity is lessened. 

 Formerly, more than at present, it was the custom 

 to estimate the quality of the milk by determining 

 its specific gravity, but as soon as it became known 

 that the specific gravity depended not so much upon 

 the amount as upon the character of the solids, a 



