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Journal of Animal Science Abstract -

Effects of Heterosis on Age and Weight at Puberty in Beef Heifers1

 

This article in JAS

  1. Vol. 25 No. 3, p. 744-751
     
    Published:


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doi:10.2527/jas1966.253744x
  1. J. N. Wiltbank2,
  2. K. E. Gregory3,
  3. L. A. Swiger,
  4. J. E. Ingalls2,
  5. J. A. Rothlisberger and
  6. R. M. Koch
  1. U. S. Department of Agriculture and University of Nebraska, Lincoln

Summary

Summary

The Hereford, Angus and Shorthorn breeds and all reciprocal crosses among them were included in an experiment that was designed to evaluate heterosis effects in crosses among these breeds.

The traits evaluated were age at puberty, weight at puberty, age at puberty adjusted for average daily gain from birth to weaning (200 days) and age at puberty adjusted for average daily gain from weaning to 396 days. Data are presented and discussed for these traits on 182 heifers from two calf crops developed to produce their first calves as 3-year-olds (low wintering level) and 171 heifers from two calf crops developed to produce their first calves as 2-year-olds (high wintering level).

Preweaning average daily gain had a significant effect on age at puberty in both management groups, while the effect of postweaning average daily gain was significant only at the low wintering level.

Breed-of-sire effects were significant (P< .01) for all traits for both management groups, while breed-of-dam effects were of greater importance for the heifers developed on a high level of wintering. Interactions with years were not important. The breed of sire by breed of dam interaction was significant (P<.01) for all traits for both management groups, while the sire-within-breed by breed-of-dam interaction was not important. Thus, the heterosis observed was a characteristic of the breeds used rather than of specific sires within breeds.

Significant (P<.01) heterosis effects existed for age at puberty. After age at puberty was adjusted for the effects of average daily gain from birth to weaning and average daily gain from weaning to 396 days, one-half to three-fourths of the heterosis effect on age at puberty was still present. Thus, there was a significant (P<.01) heterosis effect on age at puberty independent of heterosis effects on average daily gain. From these results it is concluded that there is a heterosis effect on age at puberty in addition to that exerted through average daily gain.

Heterosis effects on age and weight at puberty were greatest for the Hereford × Shorthorn and the reciprocal cross. This was consistent for both management groups of heifers.

Breed effects existed for age and weight at puberty. The Herefords were older and heavier at first estrus, while the Angus and Shorthorns were similar.

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Copyright © 1966. American Society of Animal ScienceCopyright 1966 by American Society of Animal Science