620 



PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



studied in detail directly, the amount and character of the milk depends 

 largely upon the period of pregnancy and suckling, as there is a close 

 sympathy between the secretion of the mammary glands and the genital 

 organs. The period of activity of the mammary gland is inaugurated 

 shortly before the first birth, and shortly thereafter yields the largest 

 amount of secretion, which in the best Dutch cattle may be as large as 

 30-35 liters each day. This maximum persists for several weeks, and 

 then commences gradually to decline, there being a continual and gradual 

 relative increase in the albuminoids and a decrease in the fats and sugar, 

 and at the end of the tenth month only one-quarter or one-sixth as much 

 milk is secreted as at first. During the first ten months of lactation in 

 the best cows more than 6000 liters may be secreted ; fairly good cows 

 will form 3000 liters, and poor cows not more than 1000 liters of milk in 

 the same time 



Quite frequently good cows will yield as much milk, nearly, after ten 

 months as in the first week after birth. 



Colostrum is far richer in solids than the later secretions of milk. 



Immediately after calving, 



1st day after calving, . 



2d 



3d 



4th 



5th 



6th 

 14th 

 28th 



The solids contain the following constituents : 



Immediately after calving, 



1st day after calving, . 



2d 



3d 



4th 



5th 



6th 

 14th 

 28th 



Colostrum contains 3.3 per cent, salts, and it therefore follows that 

 the percentage of casein must be 11.2 per cent. 



The quantity of milk depends upon the breed of cow. Some races 

 are good milkers, while others are better as meat producers and beasts of 

 burden. Nevertheless, the quantitj' of milk is directly proportionate to 

 the degree of development of the mammary gland. Even in two cows 

 of the sanie breed, and on precisely the same food, the amount of milk 

 secretion will depend upon the degree of development of the glandular 

 tissue. 





Solids. 



Water. 





38.4 



61.6 





30.1 



69.9 





. 23.1 



76.9 





15.3 



84.7 





14.9 



85.1 





13.7 



86.3 





12.9 



87.1 





12.6 



87.4 





12.4 



87.6 



>tituei 



Fat. 



its : — 

 Sugar. 



Albuminoids. 



8.4 



0.0 



15.5 



5.9 



0.2 



13.7 



6.2 



0.9 



10.9 



4.0 



2.5 



8.6 



4.5 



3.6 



5.1 



3.7 



3.9 



3.4 



3.0 



4.3 



2.0 



2.5 



4.3 



1.6 



2.6 



4.4 



0.7 



