Article By: Country Wide-Magazine. Source: Country-Wide

AgResearch scientists say cryptorchidism and hormone treatment options used by sheep and beef farmers to modify ram and bull behaviour, are unlikely to be adopted on deer farms.

Experiments in the past two years have shown that induced cryptorchidism and hormone suppressing vaccine treatments will modify stag behaviour during the rut, but won't stop them losing condition.

During the breeding season adult deer stags can lose up to 30% of their liveweight through lost appetite and increased physical activity such as fighting and fence paving.

Lincoln based AgResearch scientist, Alistair Nichol says stags are a danger to themselves and the environment when they are digging holes and pacing fences causing soil erosion.
"The common response is to spread them out and leave them alone but then farmers have trouble building up a pasture wedge to take them through winter."
Nichol was involved in two trials at Lincoln, which he and colleague Graham Barrell presented to the New Zealand Society of Animal Production Conference at Massey University in June.

The first was a behavioural study of entire stags compared to induced cryptorchid stags run over two years, firstly at Lincoln University then on a larger scale on six commercial deer farms. In mid January of the first year 20 mixed-age stags on the Lincoln University deer farm were split into two groups. Induced cryptorchidism was then performed on one group using lamb castration rings. The two groups were then run in adjacent paddocks and behaviour monitored for one hour, twice per week between March 23 and May 15.

These behavioural observations showed up to 50% less roaring, 75% less chasing and 50% less pacing in the cryptorchid group compared with the entire stags. There was a 3kg difference in the total liveweight lost by stags during the rut. The cryptorchid stags averaged 17kg liveweight loss, but the fact that entire stags lost 20kg was not statistically significant.

In the second part of the first experiment liveweight and condition score changes during the rut and subsequent velvet production were compared on 100 entire and 100 cryptorchid stags. These stags, which ranged from 2-8 year old were grouped on farm according to their liveweight and previous velvet weight.

There was no significant difference between the post-rut liveweight, condition score, velveting liveweight and velvet weight and grade of the two groups of stags. Both groups lost the equivalent of 10.7% of their pre-rut liveweight.

Alistair Nichol says because cryptorchidism had no effect on liveweight or condition score over the rut, even though it appeared to modify stag behaviour, it is unlikely to be picked up by farmers.

However heavier red deer stags in the study lost more liveweight during the rut.
"The fact that there was no relationship between liveweight loss over the rut and subsequent velvet production suggests that, if liveweight loss over the rut is repeatable and heritable, it may be possible to select for stags that lose little weight over the rut."

Meanwhile a second trial at Lincoln investigated whether a vaccine against a hormone responsible for antisocial fighting and riding behaviour in bull herds would also lessen the effects of the rut on stag liveweight and condition.

Barrell says clearly these factors would count against using the vaccine in a commercial situation. He says further development of a vaccine would require a product that reduces testosterone concentration to a level which influences behaviour and liveweight loss but not antler re-growth.