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Abortion in ewes, it's the 'silent killer' of lambs and the quiet nightmare for sheep producers.
Not only does it leave behind profitable losses before producers even know it has happened, multiple possible causes often make a definitive diagnosis difficult.
According to veterinarian and sheep production advisor, Dr Paul Nilon of Nilon Animal health, Tasmania, while the industry is fully aware of perinatal losses, there is still a number of gaping holes in what we know about fetal abortion and loss.
But according to the veterinarian increased use of scanning has bought the issue to the forefront.
"Until scanning was widespread, background losses were rarely noticed," Dr Nilon said.
"But now, more and more farmers are becoming aware of fetal loses in sheep."
He said farmers who may have scanned 90 per cent of ewes in lamb, when it came to marking, there were ewes that had never lambed at all.
"The things to look out for are the higher than expected scanned in lamb, but didn't lamb and the difference between what is scanned and what is actually marked," he said.
He suggested, in particular for high rainfall areas, they should be at least scanning higher than 93pc in lamb from adult ewes, but said maidens are more variable, providing they are not droughted or otherwise compromised.
He recommended working on greater than 75pc for one-year-olds and 85pc for two-year-olds.
If you're experiencing frank abortions of more than one per cent in one mob or more than 10 or 12pc across the whole enterprise, investigate them. Act early, you may be able to stave off a disaster.
"After the first three weeks pregnancies should be fairly robust, so there should only be a small variation of what is scanned in lamb and what actually lambs," Dr Nilon said.
"Look for obvious empty ewes at pre-lamb treatments, isolate and get information about serological tests."
Unfortunately though, often the surprise comes at the time of marking.
Dr Nilon recommended allowing for 17 to 22pc twin losses and 9-13pc for singles around birth.
"This is dependent on breed, weather and body condition, but if you are outside these figures, look for a reason," he said.
"If you're experiencing frank abortions of more than one per cent in one mob or more than 10 or 12pc across the whole enterprise, investigate them. Act early, you may be able to stave off a disaster."
Campylobacter is an issue that is in the forefront of Dr Nilon's mind, and said it is far more prevalent than some may realise.
Extensive blood sampling confirms two thirds of farms tested are affected by the main abortion causing strain.
An outbreak can be costly, it is highly contagious and can spread through flocks like wildfire. Any breed of sheep is susceptible and higher rainfall regions are at greater risk of the bacteria spreading.
The infection affects ewes in late pregnancy and is transmitted through contaminated food or water and can be spread between flocks and properties by carrion-eating birds and scavengers.
Dr Nilon said it is often wrongly assumed Campylobacter only occurs in maiden ewes.
"There is no doubt that maidens are the most likely to get absolutely slaughtered by the bacteria, but we have seen enough cases where there background losses and abortion storms are in older age group ewes as well," he said.
"It's not uncommon for some producers to experience 'abortion storms', which lead to lamb losses of between 25 and 50 per cent.
"These storms occur two to six weeks before lambing, and the earlier they start, the greater the damage.
"It is increasingly associated with scanned in lamb, but did not lamb - anything from a few percent to 60pc."
Dr Nilon said a flock is at a higher risk when they're in a highly congested area.
"If your running them in a tightly controlled grazing pattern or if you're drought lotting them, the best way to reduce the risk is to vaccinate," he said.
"More to the point, solid data indicates that vaccinated flocks have higher birth rates than those that are not.
"Our Kiwi friends tell us they see five to eight per cent increases in scanning rates between vaccinated and non-vaccinated flocks. At that level of reproductive performance, it's a no-brainer."
The vaccine Coopers Ovilis CampyVax is on the shelves costing roughly $1.40 per shot. It requires two shots in the first year, and an annual booster pre-joining.
When producers identify an outbreak has occurred, Dr Nilon recommended picking up all foetuses and membranes, isolating aborted ewes and spreading sheep out, if possible.
When it comes to the use of antibiotics, oxytetracycline and erythromycin are the two choices, but warned there wasn't a lot of evidence supporting their success, but said the further out from lambing, the more likely they are to work.
So, what should producers do with their aborted ewes?
According to Dr Nilon, part of the issue is the risk of the repeatability of rearing failure.
But in the case of Campylobacter he said they rarely, if ever, have infection in the uterus after the problem.
"The chances of them not getting in lamb due to residual infection is low," Dr Nilon said.
"And once you have had an abortion storm, chances are you are going to be fairly immune to it."
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