Testis function, carcass traits, and aggressive behavior of beef bulls actively immunized against gonadotropin-releasing hormone.
We assessed testis function, aggressive behavior, and carcass traits in beef bulls actively immunized against GnRH at 1, 4, or 6 mo of age. In addition, we examined the effect of combining immunization with insertion of estrogen-containing implants (Synovex C) at 1 mo of age. Unimmunized bulls and steers were included as control animals. All immunized calves received a secondary immunization at 12 mo of age. Anti-GnRH titer was evident at slaughter in all immunized animals. Neither age at primary immunization nor implant status affected (P > .05) anti-GnRH titer at slaughter. Immunization, but not implant status, reduced (P < .05) serum concentration of testosterone and testis weight at slaughter. The final live weight and feedlot gain of immunized and unimmunized bulls were comparable (P > .05). In contrast, aggressive behavior was reduced (P < .05) and carcass quality was improved (P < .05) by immunization. These data suggest that active immunization against GnRH is a practical, noninvasive alternative to physical castration in the management of bull calves.
Department of Animal Science, University of California, Davis 95616, USA.
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D000374:Aggression; D000818:Animals; D000906:Antibodies / Q000097:blood; D001522:Behavior, Animal; D002417:Cattle / Q000276:immunology / Q000502:physiology* / Q000523:psychology; D004338:Drug Combinations; D004343:Drug Implants; D004958:Estradiol / Q000008:administration & dosage / Q000031:analogs & derivatives; D007987:Gonadotropin-Releasing Hormone / Q000276:immunology*; D007117:Immunization, Secondary / Q000662:veterinary; D008297:Male; D008460:Meat / Q000592:standards*; D011374:Progesterone / Q000008:administration & dosage; D013737:Testis / Q000254:growth & development / Q000502:physiology*; D013739:Testosterone / Q000097:blood; D014611:Vaccination / Q000662:veterinary*; D015430:Weight Gain
D000906:Antibodies; D004338:Drug Combinations; D004343:Drug Implants; D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone; D011374:Progesterone; D004958:Estradiol; C025370:estradiol benzoate, progesterone drug combination