Studies in Milk Secretion 163 



sister mating). The group of sires power in their transmitting 

 qualities are consequently more inbred than the group of sires 

 with superior transmitting qualities. 



The analysis of the pedigrees for the amount of relation- 

 ship that may exist between the sire and dam of the individual 

 bulls in the superior group and in the inferior group shows 

 that there is little or no difference in the amount of this rela- 

 tionship within the two groups. 



The resolution of the four generation pedigrees into the 

 Island bred Jerseys and by difference into the American bred 

 Jerseys showed the mean number of island males in the pedi- 

 grees of the superior sires' group to be 8.07 and the mean num- 

 ber of females 7.79. The mean number of island bred males 

 in the inferior sires' group were shown to be 6.94 and the mean 

 number of females 6.55. The group of sires which increased 

 the production of their daughters over that of their dams had, 

 consequently, more island bred stock in their pedigrees. The 

 females in each group of the pedigrees had a less proportion of 

 island bred individuals than the males had in each of the groups. 



This same information on island bred animals is revealed 

 when classified as to whether the animals occur on the sire's 

 or dam's side of the pedigree that the superior sires have by a 

 small percentage more island bred animals in the sire's side 

 of their pedigree than do the inferior sires and that the supe- 

 rior sires have a larger number, probably significantly larger 

 number of island ancestors in the female side of the pedigree 

 than do the inferior sires. The figures are 8.82 to 8.19 and 

 7.04 to 5.30. The number of ancestors of island breeding on 

 the sire's side of the pedigree is in both cases larger than the 

 number of island bred ancestors on the dam's side of the pedi- 

 grees. 



These conclusions are further substantiated by a study of 

 the proportion of island ancestors in the great-great-grand 

 parents of these two groups of sires. 



Study of the pedigrees of these two groups of sires dis- 

 closes the fact that all the animals which appeared in the pedi- 

 grees of the superior sires on the male side of the pedigrees 

 more than four times or on the female side of the pedigree 

 more than three times also had appearances in the pedigrees 

 of the sires inferior in their transmitting qualities. This fact 



