Increasing the liveweights of weaner sheep before summer can bring significant gains to the wool cheque, according to recent research conducted through the Cooperative Research Centre (CRC) for Premium Quality Wool.
Dr David Masters of CSIRO Animal Production says that in a recent trial a group of weaners averaging 33 kg liveweight grew nearly 2 g more wool a day than lighter weaners averaging 25 kg. The wool had greater staple strength and only slightly higher fibre diameter.
"Despite slightly lower values per kilogram for broader wool, the advantage in returns in 1997 wool prices from the heavier weaners would have been at least $1.50 per sheep," he says.
Dr Masters says that weaners experience considerable stress over their first summer through a combination of weaning and the transition from abundant green feed to limited dry feed. They frequently lose weight over the summer-autumn period and fibre diameter can decline by 8 microns along the fibre, leading to low staple strength.
"If it comes to a choice of keeping the weaner weights up or more supplementary feeding during summer, the higher early weight will bring a greater dividend."
"The maintenance of weight through supplementary feeding will increase wool growth and staple strength, but is not usually cost effective," he says.
"Even when sheep in our trial were losing weight over summer, the heavier individuals appeared to put their nutrients into growing more wool, while the lighter ones were using feed mainly for body requirements.
"Larger weaner sheep which were losing weight tended to have a higher conversion of feed to wool than lighter weaners eating to maintain weight.
This means supplementary feed will be more efficiently used by larger weaners, and feeding costs over summer-autumn can be reduced."
Dr Masters says these findings are based on two groups of 32 weaners fed a hay-based diet under carefully controlled conditions for three months in the animal house at Floreat, then returned to the field for two and a half months before shearing.
Another experiment involving much larger numbers of weaners under farm conditions is being undertaken by Dr Steve Gherardi of Agriculture WA, at Badgingarra. Results should be available towards the end of the year and should provide further important information.
This project is supported by funding from the International Wool Secretariat through the CRC for Premium Quality Wool.
More information:
David Masters, CSIRO Animal Production (08) 9333 6691
Stephen Gherardi, Agriculture WA (08) 9368 3572
Georgina Wilson, Agriculture WA (08) 9368 3889