Two trials were conducted to study the effectiveness of vaccination of stags against gonadotrophin-releasing hormone (GnRH) for minimising the deleterious effects of the rut on their live weight and body condition. In March 2000, mature red deer stags (n = 10) received a s.c. injection of 1.0 ml of vaccine (Improvac®) or saline solution (controls) and a second injection three weeks later. Liveweight loss in the 10 weeks following the initial injection was not affected by the treatment (mean loss 28.6 ± 4.0 kg and 28.1 ± 4.2 kg for vaccinated and control groups, respectively). Plasma testosterone concentration was lower (P<0.05) in the vaccinated stags but there was no effect on scrotal diameter. In the following year, stags (n = 10) were injected with 2.0 ml of the vaccine or saline on 18 January and 8 February. Mean liveweight loss in 21 weeks was similar for vaccinated and control groups (41.2 ± 8.2 kg and 38.8 ± 7.2 kg, respectively) and there was no treatment effect on the reduction in body condition score. Although vaccinated stags had a lower (P<0.05) mean plasma testosterone concentration than control stags, this effect can be entirely attributed to stags (3 out of 4) that had been vaccinated in the previous year’s trial. It is concluded that vaccination of stags against GnRH does not overcome the loss in live weight which is associated with the rut in these animals.
Proceedings of the New Zealand Society of Animal Production, Volume 62, Palmerston North, 149-151, 2002
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