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ON INBREEDING IN JERSEY CATTLE. 



Table I. 



The English Jersey Bbeed — its Coefficients of Inbreeding by ten-year 



Periods. 



In Table I the result of the study of the English Jersey breed of cattle are shown. 

 There is no great degree of inbreeding. Further discussion of this will be published 

 elsewhere. 



Dr. J. S. Gordon, in his Presidential Address to Section M, stressed the need of 

 standards of production before livestock improvement could advance much further. 

 This was emphasised in the discussion which followed, particularly by Prof, R. G. 

 White, who stated that herd books as at present constituted, though they had served 

 a useful purpose in the past, required to add information concerning the performance 

 of the ancestors of the individuals if they were to be of continued benefit. 



With a view to finding out whether there was any connection between inbreeding 

 and productivity, especially milk yield, a list was drawn up of the pedigreed English 

 Jersey cows, born between 1916-20 inclusive, which in one lactation of less than 

 365 days gave over 10,000 lb. of milk. This list was taken from the Register of 

 Dairy Cows -with authenticated milk records compiled and pubUshed by the English 

 Ministry of Agriculture and Fisheries. Ninety-eight animals were obtained for this 

 period. Only thirty of these were traced to the Herd Book from the date of birth 

 and o'wner's name, as the pedigree numbers are not given in the Register. From 

 the English Jersey Herd Books for 1923-24—25 a list of cows was made up which 

 gave 10,000 lb. in less than 365 days. This gave an additional thirty cowa. The 

 coefiicients for these sixty cows were then tabulated. 



The pedigrees of these sixty cows gave an average co-efBcient of only 1^845, as 

 compared to the breed average for the corresponding ten-year period of 3^913±-313, 

 and for the cows of the breed boiD in that period of 4-264±-456. These differences 

 are appreciably greater than four times the probable error, and may therefore be 

 considered to be significant. Nine of these sixty cows had coefficients greater than 

 the average of the breed, ranging from 3^95 to 12^65. Twenty-seven had a coefficient 

 of less than 1*0. 



This finding is not in accord with the work of the Maine School (Pearl and others, 

 1919, Gowen and Covell, 1921-1, 1921-2, and Gowen, 1924, Chapter VII), who state 

 that high producers are equally inbred as the low producers. However, Gowen 

 (1924, p. 121) shows that in the American Holstein the sires with no advanced registry 

 daughters are somewhat more inbred than the sires of advanced registry daughters. 

 The findings of the Maine School are, however, barely comparable to those in this 

 paper, as Pearl's coefficient is employed, which is purely objective and has nothing 

 whatever to do directly with the gametic constitution of individuals. 



McPhee and Wright (1926) found no material difference in the amount of inbreeding 

 between the Beef and the Dairy Shorthorns. They did not study the high yielders. 



The examination of the pedigrees of animals in two noted Jersey herds confirmed 

 this difference, noted as regards the breed as a whole. These were the Godinton herd 

 and the herd of Mr. J. S. Gordon in Northern Ireland. 



One reason why the high yielders were less inbred than the average of the breed 

 was because the average cow of the breed was more inbred to a bull who was all 

 powerful some thirty years ago. The arrival of accurate milk recording on a large 

 scale within the past fifteen years has, however, altered the standards somewhat 

 with the quite natural result that the concentration of the blood of a bull of the older 

 standards does not help breeders to obtain in their animals the requirements of the 

 present day. This will be further discussed in a later paper. 



