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Journal of Dairy Science Vol. 59 No. 10 1817-1824
© 1976 by American Dairy Science Association ®
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Parameter Estimation and Sire Evaluation for Dystocia and Calf Size in Holsteins1

E. J. Pollak2 and A. E. Freeman

Department of Animal Science, Iowa State University, Ames 50010

ABSTRACT

Records containing calf size and dystocia scores were obtained for 12,872 and 4205 Holstein parturitions by Midwest Breeders' Cooperative and Select Sires, Inc. Calf size and dystocia were affected by herds, sires, age of dam, sex of calf, and season of birth. Size of dam was a source of variation for calf size but not for dystocia. When calf size was included in the model, it affected dystocia. Herita-bilities for dystocia were .08 ± .026 (Midwest) and .05 + .022 (Select Sires). Heritabilities for calf size were .15 ± .052 (Midwest) and .13 ± .033 (Select Sires). Genetic correlations between dystocia and calf size were .97 ± .07 (Midwest) and .89 ± .17 (Select Sires). Sires were ranked for dystocia in the Midwest data by least squares constants, least square constants regressed for numbers, selection index, and mixed model prediction using sire relationships. Sires also were evaluated for calf size by the mixed model technique. The rank correlations among the five estimation procedures with a mixed model evaluation for dystocia on an independent data set in Midwest were .73 (mixed model for dystocia), .72 (regressed least squares), .67 (selection index), .66 (least square constants), and .57 (mixed model for calf size).

FOOTNOTES

1 Journal Paper No. J-8438 of the Iowa Agriculture and Home Economics Experiment Station, Ames. Project 1053

2 Department of Animal Science, University of California, Davis 95616.






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