Cundiff L V, Núñez-Dominguez R, Dickerson G E, Gregory K E, Koch R M
Roman L. Hruska U.S. Meat Animal Research Center, USDA, Clay Center, NE 68933-0166.
J Anim Sci. 1992 Aug;70(8):2397-410. doi: 10.2527/1992.7082397x.
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 less than .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 greater than .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 less than .10) and .82 more calves (P less than .10) if all nonpregnant cows were culled. Corresponding cumulative calf weight weaned was 272 kg (P less than .01), or 25% more, and 232 kg (P less than .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 less than .05) and tended to be greater than that of Hereford cows.
对172头赫里福德、安格斯和短角牛品种的正反交杂种母牛以及156头纯种母牛，评估了母体杂种优势以及母体和祖母代品种效应，对进入繁殖群的每头母牛的累计终生断奶犊牛数量和体重的影响。1960年和1961年出生的母牛在3岁时首次产犊，1962年和1963年出生的母牛在2岁时首次产犊。分析了连续两年未怀孕母牛实际淘汰以及任何未怀孕母牛强制淘汰情况下的生产性能。随着母牛从2岁到5岁，每头犊牛和每头受胎母牛的繁殖率和断奶体重增加（P小于0.05），在5岁到9岁时达到峰值，从9岁到12岁下降。杂种优势效应与首次产犊管理时的年龄没有相互作用（P大于0.05）。在2岁首次产犊管理系统的12年期间，在实际淘汰政策下，杂种母牛比纯种母牛多产近一头犊牛（0.97头犊牛，P小于0.10），如果淘汰所有未怀孕母牛，则多产0.82头犊牛（P小于0.10）。杂种母牛相应的累计断奶犊牛体重比纯种母牛多272千克（P小于0.01），即多25%，多232千克（P小于0.01），即多30%。纯种安格斯母牛12年的累计断奶犊牛体重超过短角牛母牛（P小于0.05），且倾向于高于赫里福德母牛。
