UNMULESED sheep treated with a long-acting insecticide are protected from breech-strike but mulesed sheep are far easier to manage, a study by University of Melbourne’s Mackinnon Project has found.
And as a result, mulesing is still the most cost-effective form of long-term flystrike prevention.
Mulesing has been thrust back into the spotlight so far in 2013 following a fresh push by Animal Liberation to ban the practice, calling on Ermenegildo Zegna to abandon use of mulesed wool in its garments from 2014.
There have also been reports in metropolitan media this week that farmers were turning back to the practice because they were not receiving premiums for unmulesed wool.
Mackinnon Project director John Larsen said it was understandable that farmers would return to mulesing if there was no financial incentive in wool price or there was no effective and cheaper alternative.
“No farmer enjoys mulesing, it’s an unpleasant task but it’s so effective,” he said.
“Certainly breeding for less wrinkle and wool on the breech is quite clearly the way to go and that’s where the industry should be going aggressively. But knowing the wool industry, this will take some time to filter down to commercial flocks.
“In the past decade, use of pain relief at mulesing has increased from about 20 per cent to 70pc of flocks.
“The current product used for pain relief has only a relatively short lived effect on reducing pain. But it appears to provide some longer term benefit by assisting wound healing.”
Dr Larsen said results from the first 20 months of work in the trial – funded by Australian Wool Innovation – had been presented in July last year but had not been widely publicised, except through workshops conducted by the Mackinnon Project.
The three-year study ran from 2008 to mid-2011. It involved more than 6000 sheep in three self-replacing Merino flocks in Victoria.
It compared mulesing to breech clips and application of long-acting insecticide (Clik) to unmulesed sheep.
Dr Larsen said, on a scale of one to five, clips reduced breech wrinkle score in lambs by only 0.3 to 0.5, whereas mulesing reduced it by about 1.5 units to a score of about 1.5. These were typical wrinkly Merinos with an average breech wrinkle score at marking and weaning of 2.5-3.
He said when it came to the proportion of sheep that became struck in the high risk period before Christmas, unmulesed sheep treated with dicyclanil (Clik) had no or very little breech strike, which was equal to or better than the untreated mulesed group which had 1-10pc strikes.
The untreated clipped sheep were the most susceptible, with 3-18pc of animals getting breech strike.
“That didn’t surprise us with what we already knew from clinical experience with the clips,” he said.
“Clips provided little protection from strike during spring and early summer.
“There was no difference in the prevalence of breech strike between the mulesed and unmulesed groups but once protection from the chemical expired after Christmas, the unmulesed sheep were at greater risk of breech strike compared to both the clipped and mulesed ones.”
Dr Larsen said dag was the most significant risk factor for breech-strike in the trial. Unmulesed sheep consistently had the highest dag scores, with clipped sheep between the mulesed and unmulesed groups.
This increased flystrike risk and made crutching longer and more difficult, costing 15 cents more on average for crutching unmulesed sheep, plus there were more cuts to the breech in the unmulesed sheep.
“I would not be recommending clips for sheep in high rainfall zones," he said.
"Dags are a big risk factor for getting struck so the increased dag on the unmulesed sheep put them at far greater risk when not protected by insecticide.
"There was far less dag on the mulesed sheep and slightly less on the clipped ones.
“The strategic application of a long-acting insecticide early in the blowfly season, September or October, is a management strategy that producers could use to reduce blowfly populations and prevent breech-strike in both unmulesed and clipped sheep.
“As a sustainable strategy, you’d be reluctant to suggest solely relying on chemical for control.”
Dr Larsen said an economic analysis of the treatments on a 3000 ewe self-replacing Merino ewe flock found the clips were the least cost-effective option, at 80 cents to buy and 60c to put on. At $1.40 a head, the clips cost as much or more than a mulesing contractor. Running the unmulesed and clipped sheep increased the sheep enterprise costs by around 7pc and 9pc, respectively, compared with mulesed sheep.
The cost of clips could be reduced by reusing them, but only a proportion could be reused, they had to be collected and in some cases could only be reused once.