Experts claim genetics hold the key to worm resistance

Headshot of Bob Garnant
Bob GarnantThe West Australian
Industry experts Tony Schlink, John Karlsson, Graeme Martin (front) and Johan Greeff at DAFWA’s open day.
Camera IconIndustry experts Tony Schlink, John Karlsson, Graeme Martin (front) and Johan Greeff at DAFWA’s open day. Credit: Bob Garnant

Clean, green and ethical sheep meat and wool production is a win-win for WA sheep producers who strive for a flock that has genetic resistance to worms.

University of WA Professor Graeme Martin said sheep that were genetically resistant to worms used less chemicals, including drench treatment, produced less methane and did not require mulesing.

“The Australian sheep industry loses $600 million annually because gastrointestinal worms reduce productivity and also cause diarrhoea that attracts blowflies, leading to flystrike,” he said.

“To make matters worse, the worms develop resistance to drenches and the use of mulesing to avoid flystrike is no longer socially acceptable.”

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Professor Martin said Department of Agriculture and Food WA geneticist Johan Greeff and former senior research officer John Karlsson had tackled the worm-fly problem by breeding sheep that were resistant to flystrike and worms.

“Worm-resistant sheep are very effective but some resistant animals still develop diarrhoea because they have an allergic reaction to the small numbers of worms that persist in their gut,” Professor Martin said.

“We will be looking at the immune system of the sheep and find the cells, molecules and genes that cause the hypersensitive animals early in their life and breed for resistance to both worms and diarrhoea.”

Also involved in flystrike research, The Breeding for Breech Strike Project’s Tony Schlink said there were large differences between sire progeny groups and that some sires’ progeny were naturally very resistant to breech strike.

“Although wrinkle is an important indicator trait of breech strike, our research expelled the general myth that breeding plain-bodied sheep can be more susceptible to breech strike than normal Merinos,” he said.

“Dags and urine stain are more important than wrinkles or breech cover in uncrutched sheep, but under crutching regime, wrinkles are the most important factor making sheep susceptible to being struck.

“Odour from sheep also plays an important role in attracting or repelling blowflies.”

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