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THE INHERITANCE OF MILK-YIELD IN CATTLE. 



By JAMES WILSON, M.A., B.Sc, 

 Professor of AgriciiUure in tlie Ro3'al College of Science, Dublin. 



[Read May 23. Published June 12, 1911.] 



Until recently it was the common belief that variation among domestic 

 animals was a slow and gradual process, and that, if a breed was improving, 

 the increments of improvement from generation to generation were small 

 and frequently imperceptible. Holding this belief, the general policy of 

 stock-breeders was to persist in breeding not only from such stock as were 

 obvious advances, but also from such as were believed to be potential advances, 

 upon their parents. So, our present breeds were believed to have been 

 " developed " from an ancestry by no means noteworthy in attainments. In 

 each breed a few stock-breeders were usually pre-eminently successful, and 

 stock of their breeding or of their "blood" were largely sought after by 

 others less successful. If a great sire or dam could not be secured, then his 

 or her son or grandson, or a descendant still farther removed, was considered 

 more desirable for breeding purposes than another animal equally good or 

 even better as such, but less illustrious in pedigree. A near descendant of 

 some great sire or dam was always more desirable, of course, than another 

 more remote, for it was considered more likely to have inherited its 

 ancestors' tendency to improvement. 



This policy no doubt raised the general average, increased the number of 

 animals that were up to the average attainment, but it also produced many 

 disappointments, many that " harked back " to remote and less improved 

 ancestry, although these were forgotten in the occurrence of others high 

 above the average of their day. 



The difficulties of tiiis policy were greater when aj)plied to dairy than 

 when applied to " beef " breeds or to horses bred for strength or speed. In 

 these otlier eases the characters that determined whether a young animal was 

 likely to fulfil the purpose for which it had been bred were more obvious. 

 There was a method by which good dairy stock might have been told, 



SCIENT. PROC. K.D.S., VOL. XIII., NO. VII, P 



