J. Anim Sci.
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J. Anim Sci. 1984. 58:545-549.
© 1984 American Society of Animal Science
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An Evaluation of Bias in Estimated Breeding Values for Weaning Weight in Angus Beef Cattle Field Records. I. Estimates of within Herd Genetic Trend1,2,3,

W. A. Zollinger and M. K. Nielsen

University of Nebraska, Lincoln 68583-0908

Abstract

Genetic trends for weaning weight were evaluated in 15 purebred herds in the United States participating in the Angus Herd Improvement Records production testing program. Regression techniques were used for separate estimates of sire and dam contributions that were summed to estimate total herd trend. Sire contributions, calculated as the pooled within sire regression of weaning weight ratio on year of calf birth, ranged from .01 ± .23 to 1.30 ± .24 across the herds and averaged .51 ratio units/yr. Dam contributions, estimated as the pooled within dam regression of offspring weaning weight ratio, deviated from the contemporary paternal half-sib average ratio, on year of calf birth, ranged from .06 ± .06 to .68 ± .11 and averaged .34 ratio units/yr. A positive trend in direct effects was associated with a possible negative trend in maternal effects. The annual trend within herds ranged from .21 to 1.50 ratio units and averaged .85 units over all herds, representing 1.8 kg annual genetic gain in weaning weight.

Footnotes

1 Published as Paper No. 6985 Journal Series, Nebraska Agr. Exp. Sta., Lincoln and a contribution from Regional Project NC-1, Improvement of Beef Cattle Through Breeding Methods.

2 Appreciation is expressed to the Amer. Angus Assoc, and fifteen cooperating breeders for providing data used in this study.

3 Anim. Sci. Dept.






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Copyright © 1984 by the American Society of Animal Science.