A five-year study at the University of Melbourne has debunked the belief that shearing sheep in autumn produces stronger wool.

The study, conducted by Veterinary Science PhD research student Angus Campbell from the Mackinnon Project at the University’s Faculty of Veterinary Science, also finds that there are significant animal welfare issues caused by shearing in autumn rather than spring.

Australian wool farmers once traditionally sheared their sheep in spring but, over the past 20 years, this practice has changed with most farms shearing in autumn – driven by the belief that stronger wool fibres are obtained at this time of the year.

Mr Campbell says the idea behind this belief is that wool gets thinner in autumn and that if shorn at that time the strength of the wool will be greater because it will be thin on the ends but thicker and stronger in the middle.

However, his research, conducted over a five-year period on two farms west of Geelong with more than 3000 ewes and lambs, shows there is no improvement in the strength of wool when compared with a spring shearing.

“The research found that in ewes there are two times when the wool thins out, in autumn and when the ewes are pregnant in spring,” he reports. “This shows there is not one annual shearing time which will consistently improve wool strength.”

For his research Mr Campbell tested the wool of 1000 sheep, one third shorn in December, one third in March and another third in May.

It was an extensive project which involved taking wool samples from 5000 shearings, measuring fibre diameter and strength, and recording the weight of each fleece and the ear-tag ID of the sheep from which it came.

The sheep were also weighed and measured, and the health of their fleece assessed and checked for dags and grass seed infestation.

The researchers found that although the fleece produced in March gained the farmer about $5 or three per cent more ($160 compared to $155) over the lifetime of the sheep, there were extra animal health and welfare problems which ended up costing the farmer more to manage.

Mr Campbell says the research also uncovered important factors in improving the mortality rates of lambs over the summer months.

“This has been largely a hidden problem on many Merino farms but because every sheep in the project was identified by an ear tag we were able to assess the risk of death of lambs and identify the factors which caused deaths.’’

He says a major finding was that giving young sheep slightly extra feed supplements over summer dramatically reduced death rates.

“We have shown that if you can increase the growth rate of sheep from a quarter to half a kilo per month over the summer months, you will decrease the death rates of lambs by two-thirds.

“There are computer programs which show farmers how much to feed their flocks for a certain weight gain. Our results now show them exactly how much that weight gain should be to save lives.

“We have found that by providing an extra 1.5 kilos per head per week – which costs 25 cents – you can really save a lot of sheep lives.

“This is a major finding that will be a really powerful tool for improving the welfare of sheep,” he says.

Mr Campbell’s PhD research supervisors are Dr John Larsen and Associate Professor Andrew Vizard of the University’s MacKinnon Project.