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Beyond the Bale : Feb 07 - Mar 07 Supplement
GENETICS By Fiona Conroy The wool industry has been working for years to put more wool on sheep, but now there is a move to take some of the wool off ... around the breech. Troy Fischer, AWI's program manager for sheep productivity, says the development of naturally bare-breech Merinos could be the key to naturally and permanently reducing the incidence of breech strike. "While the search for alternatives to conventional mulesing has included clips and injectible compounds to create bareness, stretch and lift around breech and tail, another approach is to breed sheep with naturally bare breeches," Dr Fischer says. "The idea gained momentum two years ago when a ram with bare breech and crutch area, named Cojak, was found in a stud flock on the Eyre Peninsula in South Australia. "The ram was the catalyst for a project at the University of Adelaide, which looked at the trait and its heritability. Professor Phil Hynd and his team went through the flock and breech-scored and blood-sampled every animal for parentage determination by DNA technology." The project found that bareness was moderately heritable and that there was scope to select animals that were barer with finer wool. In addition, it was found that the bare-breech sheep also had a greater fleece-to-pieces ratio at shearing, because less skirting was needed. "While all this research focused on one flock in SA, there was a need to look at other sires and environments," Dr Fischer says. "Woolgrowers and stud breeders were asked to look for rams with bare breech and crutch characteristics. The response from the industry was great and we now have a selection of bare-breech rams from different environments across Australia." These rams are now the basis of a five-year breeding trial based at two sites: one run by CSIRO in Armidale, NSW, and the other by the Department of Agriculture and Food, Western Australia, at Mt Barker. The trials are examining whether sheep can be bred for breech-strike resistance and, if so, how long it takes and what the trade-offs are with other commercial characteristics such as fleece weight. Six hundred ewes are involved at each site with three different joining treatments. The joinings include 200 bare-breeched ewes to a selection of bare-breech sires, 200 control ewes joined to a selection of bare-breech sires and a control flock of 200 ewes joined to a group of control sires. Tim Dyall, of CSIRO Livestock Industries at Armidale, NSW, says the project is in its early stages with the first progeny dropped in spring 2006. Of the lambs born, half of each flock has been mulesed and half left untreated. "Every animal has been scored for bareness and wrinkle, and will be monitored to see how the scores change over time," Mr Dyall says. "This will hopefully give us an indication of the best time to breech-score animals. "Throughout the trial we will measure each animal for production traits such as fibre diameter and fleece weight while also monitoring every animal for flystrike. "To date we haven't really identified true bare- breech sires yet, apart maybe from Cojak. COJAK AND THE BARE-BREECH RAMS The progeny of rams selected for their bare breech and crutch areas will be par t of the world's largest sheep gene-mapping project "Our next artificial insemination (AI) program is in April 2007 and we still need industry to identify some new sires for us to use. "Over time we also hope to be able to use sires that we have identified in the progeny we have bred during the trial. "At the end of the five years we're hoping to have an overall picture of the heritability of a variety of breech traits, lifetime productivity and any potential management benefits of bare- breeched sheep." More detailed research into the genetics of Victorian stud breeder Phil Toland is the first to admit that breeding for a bare breech in Merinos is not going to give the wool industry results overnight. The Violet Town producer joins about 2000 Merino ewes a year and has more than 10 years' involvement in the assessment of Merino sires through the National Sire Evaluation Program. When the call went out from AWI for growers to watch out for any rams in their flock with a bare breech, one ram caught Mr Toland's eye.The ram was the result of an outcross sire used in an AI (artificial insemination) program at Toland Merinos and was extremely bare in the breech area. The ram was sent for semen collection and is one of the sires being used by Tim Dyall at CSIRO Livestock Industries in New England, NSW, and by the Department of Agriculture and Food,Western No quick fixes in breeding for bare breech Australia, in Mount Barker, to investigate bare-breech heritability. Mr Toland has been chairman of the local North East Dookie sire evaluation committee for more than 10 years.The ram's semen was also used in the Dookie sire evaluation, effectively linking all three sites. "It seemed like a good opportunity to put the ram in the trial and see what he could do," Mr Toland says. "It also meant we could trial this approach in Victoria alongside NSW and WA." The lambs sired by the ram were born at the various sites during winter and spring 2006, and have since been weaned and scored for bareness in the breech and crutch as well as for wrinkle. The crutch area assessed in the scoring system is the area between the back legs and the back of the udder in ewes, which is subject to urine stain.The 4 BEYOND THE BALE BLOWFLY SUPPLEMENT
Apr 07 - May 07
Feb 07 - Mar 07