To determine the effect of Vaxstrate®, an anti-GnRH vaccine, on the development of bull behaviour, 90 Friesian bull calves were either castrated at 2 months of age (steers, S), immunised against GnRH at 2, 2.5, 4 and 7.5 months of age (immunocastrates, I2), at 4, 4.5 and 7.5 months of age (I4), at 7.5 and 8 months of age (I7.5), or left intact (bulls, B). Immunocastration delayed the prepubertal increase in testosterone. There were no differences in behaviour between immunocastration treatments. Mounting behaviour and paddock damage for immunocastrates and steers were lower than for bulls until 13 months of age, after which there was no difference between immunocastrates and bulls, and both were higher than steers. Bulls had a higher frequency of agonistic behaviour than both immunocastrates and steers; there was no difference between immunocastrates and steers until 16 months of age, when immunocastrates scored higher than steers. Immunisation against GnRH before puberty temporarily delayed the development of sexual and agonistic behaviour of young bulls and could provide a practical alternative to traditional methods used to control bull behaviour.
Proceedings of the New Zealand Society of Animal Production, Volume 57, , 91-95, 1997
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