﻿28 



BULLETIN" 1372j U. S. DEPAETMEFT OF AGEICULTUKE 



In those daughters where both the milk yield and the percentage of 

 butterfat were increased over those of their dams, and in those 

 daughters where both the milk yield and the percentage of butterfat 

 were lower than those of their dams, there may be said to be evidence 

 of a positive correlation between the yield of milk and percentage of 

 butterfat. That is, the percentage goes up or down with the yield 

 of milk, though whether or not in the same ratio only a correlation 

 coefficient would determine. 



On the other hand, in those daughters whose percentage of butter- 

 fat increased, but the milk yield decreased, and in those daughters 

 whose percentage of butterfat decreased and the milk yield increased, 

 there may be said to be evidence of a negative correlation. That is, 

 as the milk yield increases the percentage of butterfat decreases, and 

 as the milk yield decreases the percentage of butterfat increases. 



Of the 198 daughters of these 23 sires (Table 15), 52 are better than 

 their dams in milk yield and as good in percentage of butterfat ; 67 have 

 a larger milk yield and a lower percentage of butterfat than their dams ; 

 44 have a lower milk yield and either an increased or an equivalent 



Eercentage of butterfat as compared with their dams; and 35 have 

 oth a lower milk yield and a lower |)ercentage of butterfat than their 

 dams. This would seem to offer fairly, good evidence that the milk 

 yield and the percentage of butterfat are independent in Holstein- 

 Friesian cattle, though the total number of daughters inclined toward 

 a negative correlation, 111, is somewhat greater than that of those 

 inclined tov/ard a positive correlation, 87. The uniform distribution 

 of the daughters of each sire in, these several classes would seem to 

 indicate that but few of these sires were prepotent in controlling the 

 percentage of butterfat. No sire has all his daughters in any one of 

 these classes, and only four sires have their daughters in only two 

 classes, whereas nine sires have their daughters in all four classes. 



Coefficients of correlation between the daughters of 23 sires and 

 their dams, with respect to percentage of butterfat, are given in Table 

 16. These indicate the extent to which high or low production in 

 the dam is followed by similar production in.the daughter. The 

 correlation coefficients range from —0.39 for sire N to +0.98 for 

 sire H. 



Table 16. — Correlation between daughters and dams relative to per cent of butterfat 



Sire 



Number 



of 

 daughters 



Correlation of 

 daughters to dams 



Coeffi- 

 cient 



Probable 

 error 



A-. 



5 

 13 

 12 

 9 

 6 

 9 

 7 

 6 

 6 

 20 

 6 

 11 



-0.07 

 +0.49 

 +0.34 

 +0.32 

 +0.49 

 +0.75 

 +0.31 

 +0.98 

 +0.47 

 +0.15 

 +0.52 

 -0.001 



±0,30 



±0. 14 1 



±0.17 



±0.20 



±0.21 



±0. 10 



±0.23 



±0.01 



±0.21 



±0. 15 



±0.20 



±0.20 



B 



C 



D 



E-. . -.- -. 



F 



G 



H 



I. 



J 



K 



L 





Sire 



M 

 N. 

 O. 

 P- 

 Q- 

 R. 

 S_ 

 T. 

 U. 

 V. 



w 



Number 



of 

 daughters 



Correlation of 

 daughters to dams 



Coeffi- 

 cient 



+0.93 

 -0.39 

 +0. 65 

 +0.59 

 +0.11 

 +0.94 

 +0.75 

 +0.06 

 -0.06 

 +0.79 

 +0.56 



Probable 

 error 



±0.04 

 ±0.19 

 ±0.16 

 ±0.18 

 ±0.20 

 ±0.03 

 ±0.11 

 ±0.25 

 ±0.25 

 ±0.09 

 ±0.12 



Because the daughters of most of these sires are so few in number, 

 allowance should be made in interpreting the coefficients derived. 



