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BULLETIN 1372, U. S. DEPARTMENT OP AGRICULTURE 



The daughters of sire N show stronger indications of a negative 

 correlation with respect to percentage of butterfat between daughters 

 and dams than the daughters of any other sire. To some extent this 

 is also true of his daughters with respect to their milk yield and 

 butterfat yield, as stated before. The comparative percentages of 

 butterfat of his daughters and their dams are shown in Table 20. 



Table 20. — Percentage of butterfat of daughters of sire N and their dams, indicating 



negative correlation 



Sire 



Daugh- 

 ters 



Dams 



Sire 



Daugh- 

 ters 



Dams 



Sire 



Daugh- 

 ters 



Dams 



N 



Per cent 

 3.87 

 3.78 

 3.77 



Per cent 

 3.81 

 3.54. 

 3.55 



N 



Per cent 

 3.75 

 3.71 

 3.48 



Per cent 

 4.41 

 3.71 

 3.94 



N 



Per cent 

 3.40 

 3.38 

 3.33 



Per cent 

 3.54 









4.32 

 4.41 



It will be observed that, in general, the higher-testing daughters 

 of sire N come from the lower-testing dams and the lower-testing 

 daughters from the higher-testing dams. 



WHICH PARENT HAS THE GREATER INFLUENCE ON THE PERCENTAGE OF 



BUTTERFAT? 



There are a larger number of significant correlation coefficients 

 between dams and daughters with respect to percentage of butterfat 

 than with respect to fat yield. As explained under fat yield, it is 

 doubtful to what extent a significant correlation indicates dependence 

 on either parent, because of the lack of homozygosity of the parents 

 for yield or percentage of fat. There are other indications than the 

 correlation coefficient showing that the dams do contribute to the 

 daughters' inheritance for percentage of fat. A study was made of 

 all dams to which these sires were mated that had extremes of per- 

 centage of butterfat of 3.3 or below, and 3.8 or above, and the per- 

 centage of butterfat of the daughters of the dams in these two classes. 

 There were 57 dam-daughter pairs, representing 19 sires, in the class 

 for dams having 3.3 per cent butteriat or less. The average per- 

 centage of fat for these 57 dams and daughters was 3.155 for the 

 dams and 3.314 for their daughters. There were 33 dam-daughter 

 pairs representing 13 sires in the class for dams having 3.8 per cent 

 or over. The average percentage of fat for these 33 dams and 

 daughters was 3.966 for the dams and 3.633 for the daughters. This 

 would seem to show that the dams do contribute to the inheritance 

 for the percentage of fat of their daughters. It further shows, as 

 does Table 15, that the sires also contribute to the inheritance of 

 their daughters for percentage of fat. 



The tables giving the production records of the daughters of each 

 sire and their dams have seemed to show that the daughters' percent- 

 age of fat follows that of the dams fairly closely. This might be due 

 to the following reasons : 



(1) There may be less variability in the percentage of fat than in 

 the milk yield. 



(2) The inheritance for percentage of fat may be better fixed 

 (purer) than is the inheritance for the milk yield. 



