Bagley C P, Morrison D G, Feazel J I, Saxton A M
Louisiana State University Agricultural Center, Baton Rouge 70893.
J Anim Sci. 1989 May;67(5):1258-64. doi: 10.2527/jas1989.6751258x.
A 2-yr study using crossbred male calves (n = 228) evaluated castrating at birth or at 4 mo of age and use of anabolic growth implants (none, zeranol or estradiol-17 beta). Angus, Hereford and Brahman crossbred calves produced in seven cow-calf units that varied by breed component, stocking rate and calving season were allotted to treatment at birth in a 2 x 3 factorial arrangement. Growth implants decreased (P less than .01) testicular weight and expression (P less than .05) of male secondary sex characteristics in suckling bull calves at 4 mo. Implanted calves were shorter (P less than .05) at the hips and had shorter front legs (P less than .01) at both 4 mo and at weaning. Cannon bone circumference at weaning was increased (P less than .05) by growth implants. Age at castration did not affect (P greater than .05) calf performance or body characteristics. Calves given growth implants had higher (P less than .05) rates of gain from birth to 4 mo than did nonimplanted calves (.75 vs .71 kg/d). Implanted calves were heavier (P less than .01) at weaning and had higher (P less than .01) ADG from 4 mo to weaning than did nonimplanted calves. These data indicate no benefit from delaying age at castration, but implanting increased weaning weight an average of 8.2 kg.
一项为期两年的研究，使用杂交雄性犊牛（n = 228），评估了出生时或4月龄时去势以及使用合成代谢生长植入物（无、玉米赤霉醇或β-雌二醇）的效果。在7个不同品种组成、饲养密度和产犊季节的母牛-犊牛单元中生产的安格斯、赫里福德和婆罗门杂交犊牛，按2×3析因设计在出生时分配处理。生长植入物降低了（P＜0.01）4月龄哺乳公牛犊的睾丸重量和雄性第二性征的表现（P＜0.05）。植入植入物的犊牛在4月龄和断奶时臀部更矮（P＜0.05），前腿更短（P＜0.01）。生长植入物使断奶时的管围增加（P＜0.05）。去势年龄对犊牛性能或身体特征没有影响（P＞0.05）。给予生长植入物的犊牛从出生到4月龄的增重率高于未植入的犊牛（P＜0.05）（分别为0.75对0.71千克/天）。植入植入物的犊牛断奶时更重（P＜0.01），从4月龄到断奶的平均日增重高于未植入的犊牛（P＜0.01）。这些数据表明延迟去势年龄没有益处，但植入植入物平均增加断奶体重8.2千克。
