188 ELEMENTARY AGRICULTURAL CHEMISTRY 



is a yellow liquid of strong, pungent taste, very different from 

 normal milk. It is characterised by containing small clusters 

 of cells known as *' colostrum granules," varying from '005 to 

 •025 mm. in diameter. The fat of colostrum has a higher 

 melting-point than ordinary milk fat, and contains less butyric 

 and other volatile fatty acids. Milk sugar is accompanied by 

 glucose, and the ash is greater and much richer in phosphoric 

 acid (up to 41 per cent, of its weight) and poorer in potash 

 than that of ordinary milk. 



Colostrum has been found to contain : 



Per cent. 



Fat 1-8 to 4-6 



Casein 2*6 „ 7-1 



Albumin 11-1 „ 20*2 



Sugar 1-3 „ 3-8 



Ash 1-2 „ 2-3 



Total solids 24-3 to 32-5 



Specific gravity 1'059 to 1*079 



After four or five days from calving the secretion becomes 

 like normal milk, but the colostrum granules can usually be 

 found in the milk for about fourteen days after calving. The 

 milk during the first month after calving is generally rich in 

 fat and total solids, and these diminish during the second 

 month. After the second or third month the proportion of fat 

 begins to increase, as does also the milk sugar, and this goes on 

 as long as the cow continues to give milk. The average size of 

 the fat globules diminishes with advancing lactation, but their 

 number per unit volume increases. The proportion of vola- 

 tile fatty acids in the fat has been found to diminish with 

 advancing lactation. 



The following table gives the average composition of the milk 

 of seventeen cows (dairy shorthorns), arranged according to 

 the month of lactation, embodying the results of about 700 

 analyses by the writer in 1900. 



