Heterosis for lifetime production in Hereford, Angus, Shorthorn, and crossbred cows
1992
Cundiff, L.V. | Nunez-Dominguez, R. | Dickerson, G.E. | Gregory, K.E. | Koch, R.M.
The effects of maternal heterosis and maternal and grandmaternal breed effects on cumulative lifetime number and weight of calves weaned per cow entering the breeding herd were evaluated for 172 reciprocal crossbred and 156 straightbred cows of the Hereford, Angus, and Shorthorn breeds. Cows born in 1960 and 1961 were developed and mated to calve first at 3 yr of age and those born in 1962 and 1963 at 2 yr of age. Performance under actual culling of cows nonpregnant in two consecutive years and imposed culling of any nonpregnant cows were analyzed. Reproductive rates and weaning weight per calf and per cow exposed increased (P < .05) as cows advanced from 2 through 5 yr of age, peaked at ages 5 through 9 yr, and decreased from 9 through 12 yr. Effects of heterosis did not interact (P > .05) with age at first calving management. During the 12-yr span in the 2-yr-old first-calving management system, crossbred cows produced nearly one more calf than straightbred cows under the actual culling policy (.97 calves, P < .10) and .82 more calves (P < .10) if all nonpregnant cows were culled. Corresponding cumulative calf weight weaned was 272 kg (P < .01), or 25% more, and 232 kg (P < .01), or 30% more, for crossbred cows than for straightbred cows. The 12-yr cumulative calf weight weaned by straightbred Angus cows exceeded that of Shorthorn cows (P < .05) and tended to be greater than that of Hereford cows.
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