BY H. S. HALCRO WARDLAW. 



857 



Table viii. 



Effect of number of calves or age of cow on mean composition and 



properties of its milk. 



The mean ages of the calves of the cows of different ages are 

 shown by the above Table to range from 5-5 to 3 '5 months. The 

 data given for the variation of composition and properties, with 

 the period of lactation, show that this range is small enough to 

 be without noticeable effect on the present comparisons. 



In the accompanying diagram (Text-fig. 5), the mean values of 

 the composition and properties of the milk of cows of different 

 ages, or which have had different numbers of calves, have been 

 plotted as ordinates, against the numbers of calves as abscissiie. 



This diagram shows at once that the mean values of the 

 physical properties of milk, density, freezing point, and electrical 

 conductivity are unaffected by the age of the cow. The weight 

 of milk yielded, and the percentage of sugar present are also 

 unaffected. The mean percentage of protein increases from 3*0 

 to 33 during the period examined. The mean percentage of fat, 

 on the other hand, decreases from 5*4 to 4*3, and the mean per- 

 centage of ash decreases from 0'75 to 0-62, during the same 

 period. The percentage of total solids falls, as the age of the 

 cow increases, from 14-0 to 13-2. 



