274 



Agricultural Chemistry. 



Breed. It is well known that breed is a very important factor 

 in influencing the composition of milk. The following table 

 gives the average composition of the milk from several individ- 

 uals of the breed represented. Individual variations from the 

 figures given are of course to be found, and the figures only 

 represent the general trend of the breed. 



Composition of Milk of Different Breeds. 



Individuality. It is uncommon to find in a herd of cow r s of 

 the same breed any two individuals whose milk is of the same 

 composition. This is true whether we consider single milkings 

 or the average of many. 



Age. So far as there are published data on the influence of 

 the age of cows on the composition of milk, they indicate a ten- 

 dency for the heifer to show a slightly higher fat content than 

 the mature cow. Individual exceptions, however, are not in- 

 frequent, and more data are needed to settle the question. 



Period of lactation. Immediately after calving, the first pro- 

 duct of the udder is colostrum. This is a yellow liquid, of strong, 

 pungent taste, and very different from normal milk. It is 

 characterized by containing small clusters of cells, known as 

 "colostrum granules" and is very rich in albumin. This may 

 reach 13.5 per cent. Because of the high content of albumin, 

 colostrum milk sets to a solid mass on heating. This test serves 

 to distinguish it from normal milk. This first milk is exceed- 

 ingly important to the young animal at birth, and serves to 



