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The best time for shearing

[ Research Review 0906 : Veterinary Science ]

Janine Sim-Jones

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 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.

In the past, Australian wool farmers 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.

“The idea behind this is that wool gets thinner in autumn and that if you shear 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,’’ Angus said.

However, his research, conducted over a five-year period on two farms west of Geelong containing 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 said.

“This shows there is not one annual shearing time which will consistently improve wool strength.’’

For his research Angus 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 the weight of the fleece produced.

This involved getting the fleece in the woolshed before it was weighed and thrown into a collective pile, taking a sample, then reading the sheep’s ear tag to determine from which sheep the wool had come.

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.

Angus said the research also uncovered important factors in improving the mortality rates of lambs over the summer months.

“This has largely been a hidden problem on many Merino farms,’’ he said. “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.’’

Angus said 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,’’ he said.

“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.”

Angus, who has completed a veterinary science degree, is now writing the final results of his research for his PhD, which is to be submitted later this year. His PhD is being supervised by Dr John Larsen and Associate Professor Andrew Vizard from the MacKinnon Project.

Several of his findings have been made available to farmers through the Mackinnon Project’s newsletter.

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