8 MILK AND THE PUBLIC HEALTH chap. 



marked in the milk yielded in later years.-' The quality 

 of the milk may be reduced by feeding with distillery refuse 

 and other improper food. This is sometimes done deliberately, 

 as the quantity of the milk is thereby considerably increased 

 but at the expense of the quality. Excessive quantities of 

 turnips may act somewhat similarly. 



5. Influence of the Individual Cow and the Physiological 

 Condition of the Cow. — Individual cows vary considerably as 

 regards their milk-producing qualities, the milk of some being 

 much richer in the different solids than others, and this apart 

 from breed, age, or period of lactation. The age of the cow 

 considerably influences the milk. According to Fleischmann ^ 

 the milk-yielding capacity of a cow increases up to her eighth 

 year. 



The following table from Speir ^ shows the fat content of a 

 number of cows of different ages : 



Ayrshire Milk Record Societies. 



The period of lactation markedly affects the quality and 

 quantity of the milk. With ordinary well-fed cows the per- 

 centage of total solids in the milk nearly always rises with 

 the advance of the lactation period. This is especially shown 

 as regards the fat. The actual milking capacity of the cow 



1 For example, see Bulletin No. 69, Maryland Agric. Exp. Station, 1900. 



2 The Book of the fain/, 1896. 



^ Journ. Highland Agric. Society, 1908. 



