Cojak and the bare-breech rams
The progeny of rams selected for their bare breech and crutch areas will be part of the world's largest sheep gene-mapping project
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.
"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 the bare-breech trait is under way at the Falkiner Research Station, NSW, as part of the sheep gene mapping project. Cojak is one of 20 rams being used to generate 5000 progeny for the project, all of which are being measured for more than 100 traits including breech score, wool and meat characteristics and parasite resistance.
"The project is the largest sheep gene-mapping project in the world," Dr Fischer says. "Every lamb in the project has been blood-sampled and will be genotyped to help identify which DNA markers explain variation in which traits.
"Ultimately this could result in information that would allow breeders to blood-test their animals to identify which ones were carrying genes for characteristics such as bareness, which may not express themselves until later in the animal's life."
This technology could speed up sheep breeding where progress has traditionally been slow.
"Genetics is a long-term approach, but it could offer the wool industry a long-term solution," Dr Fischer says. "In the future, woolgrowers will be able to select rams using Australian Sheep Breeding Values for resistance to breech strike."
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