“What did you do at work today?” is always an interesting question to ask a vet. The job is so varied that you can never be quite sure what the answer will be.
At this time of the year a common answer is “We vasectomised a few rams”, to which I normally receive a look of disbelief. Why on earth would we want to be doing that? However, vasectomised animals have an important role on sheep farms.
Most farms will start lambing in late March/early April and aim for a lambing period of around six weeks. This means that rams must be out at the beginning of November and all ewes must be cycling at this time. A ewe will come into oestrus approximately once every 17 days so this gives her less than three chances to conceive.
So why don’t we just have a slightly longer lambing period?
Bacteria and disease can build up in the sheds, leading to sick lambs and lameness and infections in ewes. It is also an extremely exhausting time of year. Farm workers must be on standby at all times to aid any animals in difficulty. Some farms will lamb upwards of 800 ewes and fatigue quickly sets in.
Instead, we look to get all ewes cycling at the same time. For some units this involves hormonal manipulation using drugs, but this is often not cost or time effective.
The presence of a male animal will cause ewes to start cycling and they become synchronised with each other. However, until synchronisation occurs we don’t want any to conceive. By vasectomising the ram he retains his male hormones and characteristics, but is infertile. The ‘teasers’ go in for 10 days before the fertile rams are introduced.
By the time the rams go in the ewes will be cycling together, resulting in quicker conception and a more compact lambing period.