Active immunization of young male calves and post pubertal bulls against lhrh with various conjugate doses

Abstract

In comparison to steers bulls slaughtered at the same age have produced 14% more carcase gain and 20% more lean meat. Immunological castration which is reversible may reduce aggressive behaviour and maintain the performance advantages of bulls. Active immunization against luteinising hormone releasing hormone (LHRH) reduces LH and testosterone production and, therefore, aggression in bulls (Robertson et al. 1982). However, a controlled predictable response to vaccination has not been achieved. This may be due to suboptimal choice of a number of variables in the vaccination programme. This study investigated the effect of conjugate dose and age of the animal on the anti-LHRH antibody response in bulls.Synthetic LHRH (UCB Bioproducts) was conjugated to keyhole limpet haemocyanin (KLH) (Sigma Chemical Company) using a modification of the novel carbodiimide method reported by Deen et al. (1990). New batches of conjugate were prepared for each vaccination. The efficiency of incorporation of radiolabelled LHRH varied between 40 and 45%.