Effects of Heterosis on Reproduction in Hereford, Angus and Shorthorn Cattle 1,2
نویسنده
چکیده
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). This difference was due to significantly (P < .01) higher pregnancy rates and first ser-
منابع مشابه
Germplasm evaluation in beef cattle-cycle IV: birth and weaning traits.
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Postweaning growth, puberty, and pregnancy traits were evaluated for 783 F1 heifers sired by Angus, Hereford, Charolais, Shorthorn, Galloway, Longhorn, Nellore, Piedmontese, and Salers bulls and out of Angus and Hereford dams in Cycle IV of the Germplasm Evaluation (GPE) Program at the U.S. Meat Animal Research Center. The Hereford and Angus sires included a sample of bulls born from 1982 to 19...
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تاریخ انتشار 2007