30 July 2002 Can farmers stop injuries from the rut?

During the breeding season, adult deer stags that are farmed primarily for production of velvet antlers undergo changes in physiology and behaviour which impose a risk to their welfare.

Over this time stags can lose up to 30% of their weight because they don't eat and have increased physical activity such as fighting and fence-pacing etc. Each year, as a result of this activity some deer are injured, with subsequent losses in production.

It can be dangerous for humans to intervene and also pasture management is compromised.

Dr Graham Barrell and other researchers from the Animal and Food Sciences Division at Lincoln University have attempted to modify these breeding season-related changes by using immunocastration to suppress reproductive signals to see if this helps decrease these negative effects.

This trial used adult red deer stags from the Deer Unit at Lincoln University.

"The results from this trial showed stags in the trial had the same weight loss and reduction in body condition score as the control animals even though the levels of testosterone were significantly reduced in the vaccinated stags," said Dr Barrell.

"The vaccinated stags also had a high incidence of short term skin lesions at the treatment site and some lost their antler buttons and grew velvet antlers."

"While these results were not clear-cut they do not, however, rule out immunocastration completely as a way of reducing the deleterious effects of the rut in stags in the future," said Dr Barrell.

"Further research needs to be done using a vaccine that reduces testosterone concentration to a level which may positively influence behaviour and live weight loss, but not the point where it induces regrowth of antler velvet."

These trials took place over two years. In autumn 2000 ten stags were given a first injection of a commercial vaccine (usually used for preventing boar taint in pigs) that was repeated three weeks later. Another ten stags received injections of saline solution at the same times (control animals). The trial was repeated in autumn 2001 with another group of ten stags.

Live weight, body condition and observations of behaviour were taken for each stag. Blood samples were also taken to measure the levels of testosterone in the stags.

These results were recently presented at the New Zealand Society of Animal Production conference held in Palmerston North.

This work had the approval of the Lincoln University Animal Ethics Committee.

Janette Busch, Technical Writer, Animal and Food Sciences Division, Lincoln University, Canterbury, New Zealand.