J. Anim Sci.
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J. Anim Sci. 1974. 38:711-727.
© 1974 American Society of Animal Science
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Effects of Heterosis on Reproduction in Hereford, Angus and Shorthorn Cattle1, 2,

Larry V. Cundiff3, Keith E. Gregory3 and Robert M. Koch4

U. S. Department of Agriculture and University of Nebraska, Lincoln 68503

Abstract

Effects of heterosis on reproduction were evaluated in a comprehensive experiment comparing straightbred Hereford (H), Angus (A) and Shorthorn (S) females to reciprocal cross females among these breeds when mated to produce crossbred calves with equal additive and non-additive genetic composition. This phase of the experiment involved 570 matings (cow-years) of straightbred cows and 687 matings of crossbred cows accumulated over six breeding seasons, 1962 through 1967. Approximately one-half of the cows were developed and managed to calve first as 2-year-olds and one-half as 3-year-olds, to evaluate the effects of heterosis expressed from 2 through 6 years of age and 3 through 8 years of age in each management regime, respectively.

Analyses over all breeds, ages and systems of management revealed that the effects of heterosis significantly (P<.05) reduced the interval from parturition to first estrus and the average date of conception.

Calf crop weaned was 6.4% greater for crossbred than for straightbred cows (P<.01).

Footnotes

1 Published with approval of the Director as Paper No. 3522 Journal Series, Nebraska Agricultural Experiment Station. Contribution from North Central Regional Project NC-1, Improvement of Beef Cattle Through Breeding Methods.

2 The authors gratefully acknowledge the assistance of J. N. Wiltbank, R. D. Humphrey and C. W. Kasson in collection and D. D. Dearborn in compiling for analysis the data used in this study.

3 U. S. Meat Animal Research Center, North Central Region, A. R. S., Clay Center, Nebraska 68933.

4 Department of Animal Science, University of Nebraska, U. S. Meat Animal Research Center, Clay Center, Nebraska 68933.






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Copyright © 1974 by the American Society of Animal Science.