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Journal of Dairy Science Vol. 55 No. 12 1735-1740
© 1972 by American Dairy Science Association ®
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Regression of Daughter and Herdmate Milk Yield on Genetic Value of the Herdmates' Sires

H. D. Norman, B. T. McDaniel1 and F. N. Dickinson

Animal Physiology and Genetics Institute, USDA, Beltsville, Maryland 20705

ABSTRACT

The effect that average genetic value of the herdmates' sires has on daughter deviation from herdmate average and consequently upon sire summaries was examined. Lactation records from a national sample of herds from five breeds on official Dairy Herd Improvement testing were used. Regressions within sire, within year of calving of a) daughter yield, b) various herdmate averages, and c) daughter deviations from herdmate averages on average Predicted Differences of the herdmates' sires were calculated.

As average Predicted Difference for herdmates' sires in artificial insemination (AI) increased, so did first lactation daughters' yield (b = .35 to .73) and AI herdmate average (b = 1.34 to 1.78), but the daughters' deviation from AI herdmate average decreased (b = –.72 to –1.14). Standard errors showed that these latter regressions were not different from minus one. Regression using artificial insemination contemporaries in both first and second lactation gave results similar to those expected. These results indicate that differences between bulls in the genetic value of herdmates affect present sire summary procedures and cause some misrankings among bulls. These regressions provide evidence that adjusting for the average genetic value of the herdmates' sires would significantly increase the accuracy of herdmate comparison sire summaries.

FOOTNOTES

1 Present Address: Animal Science Department, North Carolina State University, Box 5127, Raleigh 27606.






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Copyright © 1972 by the American Dairy Science Association ®.