652 



Breeding Dairy Cattle. 



[Oct. 



defect lessens the value of the work of the societies as an aid to 

 the study of the inheritance of dairy qualities and to breeding 

 in general. With regard to constitution (e), it may be inferred 

 that no cow will give high milk yields and breed annually for, 

 say. five or more years unless she possesses a very sound con- 

 stitution, but the maintenance of constitutional vigour is closely 

 associated with conditions of rearing, 'housing, feeding and the 

 risk of incurring infectious or contagious disease. The question 

 of feeding is important, since a heavy milker may break down 

 after a few years if she has been poorly fed. 



With regard to the correlation between the other qualities, 

 the opinion is commonly held that a large milk yield is usually 

 associated with a low percentage of fat. and vice versa, and that 

 heavy milkers are less regular breeder? than those giving lower 

 yields. The actual correlation between these and other points 

 can only be arrived at after careful study of a large amount of 

 information, but the breeder is not so much interested in the 

 degree of relationship found in a large number of animals 

 between, say. large milk yield and high fat content, as in the 

 discovery of individual animals which possess both these 

 qualities. If it be a general rule that high yields are associated 

 with low fat content, it is the exceptions to the rule that form 

 the breeder's opportunity for the improvement of his herd. Such 

 exceptions are fairly numerous. 



In this connection it is important to record the conclusion 

 of Professor Wilson.* after the study of several thousands of 

 records of Ayrshire cows, that the inheritance of quantity and 

 quality — high yielding capacity and fat percentage — are 

 independent of each other. It should, therefore, be possible to 

 unite in the progenv of selected parents the two qualities of 

 large yield and high percentage of fat. 



Inheritance of Dairy Qualities. — This conclusion leads 

 directly to a consideration of the inheritance of dairy qualities. 

 Can it be said that cows which are found to possess one or more 

 of the qualities referred to pass these on unfailingly to their 

 progeny? Every breeder knows his own disappointments in 

 this matter. Cows with high records, even when mated with 

 most carefully selected bulls, fail to transmit their qualities to 

 their offspring, while others with moderate records have progeny 

 which excel their dams. As illustrations of the uncertainty 

 which is often met with, the following details, taken from the 



* Scientific Proceedings of the Royal Dublin Society, Vol. XII. (X.S.), No. 35, 

 July, 1910.' 



