40 Variations in Milk. [april, 



ence to their total production in relation to their calving time, 

 from which it would seem that cows calving in March gave the 

 highest milk yield, and also the largest quantity of fat, and in 

 general that summer carvings, from May to September, gave the 

 poorest results, whilst the remaining months, from October to 

 April (with the exception of November) gave the highest yields, 

 both in milk and in butter-fat. These gave the following 

 results : — 



Number of 

 Records. 



Month of 

 Calving. 



Total 

 Milk Yield 



in the 

 Lactation 



Period. 



Percentage 

 of Fat. 



Actual Quantity 

 of Butter Fat. 







Litres. 





Kilos. 



79 



January 



2,285 



3-68 



84-2 



57 



February 



2,256 



3-68 



83-0 



6i 



March' 



2,342 



371 



897 . 



56 



April 



2,287 



370 



84-6 



71 



May 



2,183 



3-61 



78-9 



69 



fune 



2,176 



3-69 



80-3 



79 



July 



2,176 



371 



8o-8 



8i 



August 



1,991 



376 



74 '9 



82 



September 



2,082 



378 



78-8 



78 



October 



2,288 



3 '60 



82-4 



100 



November 



2,087 



3-65 



76-3 



78 



December 



2,330 



3-65 



84-9 



From the information collected in the course of the investiga- 

 tion, an attempt is made to trace the effect of heredity, and 

 more particularly the influence of the bull on the milk yield of 

 its offspring. This was done by comparing the milk yield of a 

 number of heifers got by the same bull with the milk yield of 

 their respective dams, a number of corrections, based on the 

 foregoing investigation, being made to make the two sets of 

 figures as comparable as possible in respect of age, date of 

 calving, &c. It was found that in the case of fifty-five heifers 

 got by the bull " Bill " the average fat content of their milk 

 was 377 per cent, compared with 3-57 per cent, for the milk of 

 their dams. Twenty-one heifers by the bull " Malte " also 

 showed a fat content in their milk of 0*24 per cent, more than 

 their dams (376 per cent, against 3-52 per cent.), and similar 

 results were shown by twenty-one heifers by the bull Ossian." 

 One bull was shown to have exercised a reverse effect, five heifers 

 produced by him giving 0-45 per cent, less fat in their milk 

 than their dams. 



