J. Anim Sci.
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J. Anim Sci. 1987. 64:983-991.
© 1987 American Society of Animal Science
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Genetic Trends Due to Bull Selection and Differential Usage in the Simmental Population1

M. A. Elzo2, E. J. Pollak and R. L. Quaas

Cornell University, Ithaca, NY 14853

Abstract

Records for calving ease and weight traits from 839,292 Simmental calves were used to obtain expected progeny differences of 11,130 Simmental bulls. Yearly weighted and unweighted means of the bulls' expected progeny differences for both direct and maternal effects were computed. These were used to study the trends in availability and bull usage between 1973 and 1984. The traits considered were first-parity calving ease, birth weight, weaning weight and yearling weight. The trends for both the weighted and unweighted means of the sire direct effects were positive for first-parity calving ease, weaning weight and yearling weight, but negative for birth weight. Trends in the unweighted means for direct effects for bulls represented as maternal grandsires were similar to that observed in the sires. Trends in the maternal effects were positive for first-parity calving ease and birth weight but showed almost no change for weaning weight. In each year bulls used on heifers had a higher first-parity calving ease and lower birth weight, weaning weight and yearling weight expected progeny difference means than those used on cows. Similarly the expected progeny differences of bulls mated to base dams were higher for first-parity calving ease and lower for birth weight, weaning weight and yearling weight than the predicted differences of bulls used on Simmental females. This indicates that selection of sires differed depending on the age and percent Simmental of the cow to be bred.

Footnotes

1 This research was funded by a grant from the Amer. Simmental Assoc, Bozeman, MT.

2 Dept. of Anim. Sci., Univ. of Florida, Gainesville 32611.

3 Dept. of Anim. Sci.






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