ON INBREEDING IN JERSEY CATTLE. 651 



Sex Linkage akd Milk Yield. 



Some ten of the sixty high producers were more inbred than the average of the 

 breed as a whole. Examination of these pedigrees along vrith those of the two herds 

 already mentioned led the writer to believe that there was an indication that one 

 or more factors governing the yield of milk, and perhaps quality, might be sex linked. 

 Inquiry of several breeders strongly confirmed this idea. Several herds proved to 

 be working along these lines. 



The inheritance of milk must depend on many genetic factors. Gowen has shown 

 that yield is definitely correlated to such heritable characteristics as weight, body 

 length, body width, body girth, hip height, shoulder height and rump length. In 

 addition various other heritable characters which are more diflScult to measure 

 undoubtedly affect the total yield. Amongst these are the size and shape of the 

 udder, the size and tortuousness of the milk veins, the ' touch ' of the hide, temper of 

 the individual, &c. 



Many of these characteristics are governed by entirely different factors in the 

 germplasm, and while it is not reasonable to expect that the majority of the factors 

 are inherited in a sex linked manner, it is at least permissible to speculate upon the 

 results were one or two of the more important inherited in this manner. In cattle 

 the male is the heterogametic sex and, if the above assumption is made, then 

 inbreeding to a prominent and proved sire through his sons would have no effect in 

 concentrating the sex linked qualities of that sire. To a less degree inbreeding to a 

 prominent cow through her daughters would not be so productive as inbreeding to 

 her through her son or to the bull through his daughter. Thus a statistical analysis 

 of inbreeding might give an entirely erroneous idea of the situation. 



FlOITRE II. 



Inbreeding and Sex Linkage. 



In cattle the male is the heterogametic sex. 



-J. ,o"c -. ,Violettes Aurelius. 



g. dam 



Mystole Veronica 

 vol. 30, p. 88 



Violettes Aurelius. 



Mam J 



Coefficient to Violettes Aurelius = 6.2.5. 

 Sex linked character present from Violettes Aurelius. 



.Violettes Aurelius 



(2) rn_- 



\ 



, Violettes Aurelius. 

 , g. sire • 



dam-^ 



Coefficient to Violettes Aurelius = 6.25. 

 No sex linked character present from Violettes Aurelius. 



The two pedigrees in Figure II are an example of this. The first shows sex linkage, 

 and was a type of pedigree found amongst the few inbred high producers. The second, 

 though equally inbred to the sire Violettes Aurelius, does not show sex linkage. 



