This study aimed to raise GnRH antibodies in young bulls (immunocastration) and determine the subsequent effect on behaviour, sexual development, carcass characteristics and meat quality. Thirty Friesian bull calves were assigned to one of three groups balanced by liveweight (control bulls, immunocastrates and steers). At nine months of age (Day 0) immunocastrates were vaccinated against GnRH (Vaxstrate) and boosted one month later (Day 31). Following immunisation there was a rise in GnRH antibody titre and a decrease in testosterone. Control animals gained significantly more weight than immunocastrates and steers in the first 157 days. Overall there was no difference in weight gain between controls and immunocastrates. Mean scrotal diameter of immunocastrates decreased from Day 31 to Day 110 and then rose to reach a diameter similar to those of the control bulls by Day 322. Leg wear scores were lower for treated animals compared to controls until Day 230 of the trial, although these differences were not significant. Immunocastrates had a significantly higher mean ultimate pH than both control bulls and steers. Bulls were significantly leaner than immunocastrates, and both groups were leaner than steers.
Proceedings of the New Zealand Society of Animal Production, Volume 55, , 141-144, 1995
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