A newly recognised condition in lambs has researchers on their toes as they try to get to the bottom of an increasing number of reports of fainting lambs.
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As part of work into the behaviour, the NSW Department of Primary Industries and sheep industry consultancy, Sheep Metrix, are urging sheep producers to contact them if they suspect they have had sheep or lambs that appear to be fainting.
A key thing for us is to be able to identify those lambs when they are seen, so we can take a DNA sample. Whether it's at the time, or at least if the lamb can be identified, so we can go back and get a sample at some point.
- Sally Martin, Sheep Metrix
The condition, known as Myotonia congenita, is characterised by the involuntary contraction of muscles when an animal is startled or excited.
It was brought to the attention of Dr Brendon O'Rourke, team leader of biotechnology at NSW DPI, after a breeder in North West NSW made contact with an LLS district vet about the condition in 2020.
Dr O'Rourke said the condition was known in goats and commonly known as fainting goat syndrome.
"It is caused by an abnormal chloride ion transfer in the muscle which causes delayed relaxation after contraction," they said.
"When animals with the condition are startled or excited, the muscle involuntarily contracts, becomes stiff and they may fall over temporarily. The animal doesn't faint or become unconscious."
After collecting samples and testing, Dr O'Rourke said the DPI found what was thought to be the contributing factor of the condition.
However, researchers were unaware of how prevalent the condition was within the Australian sheep population.
"Our research is only really on a single flock at this stage," he said.
That led Dr O'Rourke to sheep consultant Sally Martin, Young, and her team at Sheep Metrix.
Sheep Metrix had been looking for producers who had seen the condition in their sheep.
Ms Martin said the condition landed on her radar three years ago, with the main focus for her team being what the family tree pedigree was for the affected animals.
"My understanding is the animals grow out of it," Ms Martin said.
"It's more something we will see in young animals, particularly if they are being brought in for lamb marking or weaning.
"But in our cases we're not seeing it later on.
"We're not seeing that it's creating any major issues with productivity at the moment."
She said an ear notch sample was adequate for submission for testing if producers suspected they had lambs presented with this behaviour.
However, for the research component with the NSW DPI, Dr O'Rourke also was keen to be able to visit the farm and conduct post mortems on the affected animals, along with electromyography (EMG) to measure electrical currents to try and understand what could be happening within the affected muscles.
"We've only observed this in Merinos," Dr O'Rourke said.
"These were older sheep that we were working with."
Ms Martin said, like NSW DPI, her team have seen it in Merinos but prominent in one particular area.
"A key thing for us is to be able to identify those lambs when they are seen, so we can take a DNA sample," Ms Martin said.
"Whether it's at the time, or at least if the lamb can be identified, so we can go back and get a sample at some point.
"Then it's just really a matter of us starting to piece things together."
Dr O'Rourke said the reaction generally happened when the sheep were put under stress or were frightened in any way, with not all of them falling all at once, but a number of them.
"It was important that we observed the phenotype of the sheep to know we had samples from an affected individual that was displaying the condition," he said.
While the condition itself isn't lethal, Dr O'Rourke said, there was some concern with animals dying due to misadventure.
"Say if they were in a situation where there were 1000 other animals around them or on the move and they had a seizure, there would be the potential for them to get trampled," he said.
"So from an animal welfare perspective, they were some of the concerns."
Dr O'Rourke said the team hadn't found any cases where animals being trampled is evident but the condition is an undesirable trait.
"The animal recovers quite quickly," he said.
"The key information is now that we know what the DNA variant is that is responsible, it creates an effective management tool through DNA testing.
"So I would be more than happy for implicated breeders to reach out to us, should they need assistance to manage affected animals within their flock."
