The effect of immunocastration 7 weeks before slaughter on the behaviour, growth and meat quality of post-pubertal bulls

Active immunization against gonadotropin-releasing hormone (GnRH), commonly known as immunocastration, has been proposed as an alternative to traditio nal methods of castrating bulls. This study evaluated the effects of immuno castration on growth, behaviour and meat quality of post-pubertal bulls. Bu lls mere either vaccinated against GnRH (no. = 30, I) or left intact (no. = 30, B). A third treatment consisted of steers (no. = 20, S) that had been castrated pre-pubertally. The animals were run in eight single treatment gr oups (no. = 10 per group), three of each of B and I and two groups of S. An ti-GnRH antibodies developed and plasma testosterone concentrations decline d in I following immunization. Aggressive behaviour of I declined to be low er (P < 0.05) than B and no different from S, 5 weeks after primary immuniz ation. Seven weeks after immunocastration all animals were slaughtered. The hot carcass weight of I was between that of B and S but not significantly different from either. There were no effects of treatment on pH(u) or meat colour measurements. Taste panel assessment rated I higher than B, but lowe r than S for tenderness, juiciness and overall palatability. These results demonstrate that immunocastration of post-pubertal bulls 7 weeks before sla ughter is a potential means of reducing problematic bull behaviour and impr oving meat quality although this is likely to be at the cost of reduced wei ght gain.