Veterinary Centre Oamaru veterinarian Dave Robertson was the final speaker at a Beef + Lamb field day on Simon and Kirstin Engelbrecht’s farm in East Otago last week.
Conditions for growing feed in East Otago had been good in autumn, so there was potential for some animal health issues, he said.
"Ewes are gaining weight at the moment, so it is probably going to be a bearing year."
A study revealed a ewe was more at risk of a vaginal prolapse in spring if it gained weight between mating and scanning.
"We are in that space now."
Ewes putting on weight at this time of the year were most likely laying down fat in their abdomen.
A study showed shearing ewes in the middle of winter reduced the risk of bearings.
Theories for this included the ewes burning abdominal fat for heat production by running around after shearing.
He believed it was more to do with the ewes having more exposure to the sun and absorbing more vitamin D through their skin.
The nature of the bearings meant there was never just one thing which caused the condition.
"Meaning there will not be one thing that fixes it."
A vaginal prolapse was a function of internal pressure and vaginal wall integrity, Dr Robertson said.
The internal pressure changes in the abdomen came from the rumen, bladder, uterus, abdominal fat and gravity.
"There is only so much room in a sheep’s gut and the more things you put in, the more pressure."
A ewe carrying triplets was 11 times more likely to prolapse than a ewe carrying a single lamb.
A ewe carrying twins had five times the risk of a bearing than a ewe with a single lamb.
If the feed of a ewe was changed, or it was bulk feeding, the risk of a bearing increased because its rumen expanded rapidly and produced more methane gas until it was fully adjusted to the feed.
A study showed ewes on single-day breaks of feed had more bearings than ewes on four-day shifts.
Ewes sitting down for long periods and eating feed with high water content, such as fodder beet and swedes, could be at a higher risk of a prolapse.
A reason for this was probably a combination of increased rumen pressure and a full bladder.
Mr Engelbrecht said to combat this he got his huntaway to run through the ewes laying down on a crop to get them to stand up.
"The next minute they are all peeing and the bearings plummeted, just because I made the lazy huas stand up and have a pee."
