Growth and sexual characteristics of suckling beef calves as influenced by age at castration and growth implants.
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.
Bagley
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Louisiana State University Agricultural Center, Baton Rouge 70893.
Morrison
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Feazel
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Saxton
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AM
D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D002417:Cattle / Q000254:growth & development* / Q000502:physiology; D004343:Drug Implants; D004958:Estradiol / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D009919:Orchiectomy / Q000662:veterinary*; D009929:Organ Size; D012118:Resorcinols / Q000494:pharmacology*; D013737:Testis / Q000033:anatomy & histology; D015029:Zeranol / Q000008:administration & dosage / Q000494:pharmacology*
D004343:Drug Implants; D012118:Resorcinols; D004958:Estradiol; D015029:Zeranol