SHEEP with diarrhoea are under the microscope of Western Australian and Chinese researchers exploring new ways to reduce the risk of fly strike.
A pair of Chinese scholars has been assisting the WA researchers to distinguish between types of diarrhoea in sheep at the laboratories of the Department of Agriculture and Food and the University of Western Australia as part of the breech strike project funded by Australian Wool Innovation.
DAFWA said associate Professor Dr Mengzhi Wang and Dr Zhongquan Zhao have been supervised by department senior veterinary immunologist Dieter Palmer to help develop a test to determine the difference between diarrhoea caused by high worm burdens and hypersensitivity diarrhoea caused by an immune response.
Project leader Johan Greeff said it was important to identify the difference between the two types of diarrhoea to assist sheep selection to breed sheep that were resistant to fly strike.
“We currently have Australian Standard Breeding Values (ASBVs) to select sheep with low worm burdens to reduce the risk of diarrhoea due to gut damage, which attracts flies.
“But that selection process may increase diarrhoea, due to a hypersensitivity to immature worm larvae,” Dr Greeff said.
“If we can determine the underlying immunological causes of hypersensitivity diarrhoea, a test can be developed to identify these sheep and then develop an ASBV to select against them.”
Dr Zhongquan Zhao has returned to China, but associate Professor Dr Mengzhi Wang will continue his work until October.
Dr Greeff said that hypersensitivity diarrhoea was not a significant problem for sheep in China. However, it was an issue for WA sheep producers in winter rainfall areas.
“Sheep producers can minimise the risk of diarrhoea and breech fly strike by crutching and jetting with an insecticide and drenching worms.
“However, drenching will not help sheep with hypersensitivity diarrhoea, as the condition is due to an immune or allergic response and will continue regardless of treatment,” he said.
“This research is a long term investment that aims to eventually develop a test to identify sheep with hypersensitivity diarrhoea, which could be automated to make the selection process more accurate, easier and quicker.”
Australian Wool Innovation productivity and animal welfare program manager, Geoff Lindon, commended the researchers’ work.
“The project investigating breeding for breech strike resistance has shown the importance of breeding for both reduced worms and reduced dags, which will generate far reaching benefits for both the welfare of the animal, as well as its commercial value,” he said.
For more information visit agric.wa.gov.au and search for ‘genetic selection’ or ‘fly strike’ or consult the Sheep Genetics website.
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