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Beyond the Bale : Dec 08 - Jan 09
14 Genetics Beyond the Bale Gene technology to deliver advanced selection tools Developments in sheep genomic technology are changing sheep breeding, meat and wool quality parameters and farm productivity By Fiona Conroy reproduction are just a few of sheepGenomic’s tools under development, says outgoing program director dr rob forage. dr forage began work with sheepGenomics four- and-a-half years ago and has seen rapid developments in genetic technology, which have been incorporated into the program. sheepGenomics is a $30 million joint initiative of AWi and meat and livestock Australia (mlA), working with 11 leading research organisations from Australia and new Zealand. the program also draws on scientific expertise in the Us and the Uk. “We’ve seen the rate of genetic technology change G rapidly in recent years,” dr forage says. “several technologies that weren’t available when we started are now routinely being used.” While the research team has not mapped the entire sheep genome, it has produced a ‘virtual’ sheep genome using the genomes of the horse, cow, dog and human as guides to align the partial genomes of a number of sheep from different breeds. this has led to the discovery of more than 300,000 gene markers in the sheep genome, of which 60,000 have been selected for evaluation as enetic markers that identify superior animals, feed additives that turn genes on and off, and technology that accelerates genetic commercial production markers. these dnA markers are called snps (single nucleotide polymorphisms). the sheepGenomics team hopes to find links between some of these 60,000 snps and commercially important traits such as growth, reproduction, wool and meat quality, and parasite resistance by testing dnA obtained from the skin or blood samples of 4,000 sheep. these sheep have been measured for multiple production traits at AWi’s falkiner memorial field station in the riverina. dr forage says identifying specific gene markers for commercially valuable traits paves the way for the production of a simpler snp panel containing a few hundred markers. it will be available for use by stud breeders within two years. “snp technology has many advantages in areas such as pedigree testing and in breeding for traits that are expensive, difficult to measure or can be measured only once the animal reaches maturity. “dnA marker information can improve the accuracy of progeny test programs and will give breeders valuable information about animals at birth, speeding up breeding programs and the rate of genetic progress by allowing breeders to identify superior animals earlier.” information on an individual animal’s genetic markers could also be fed into a national database to help produce marker-assisted Australian sheep breeding values (Asbvs), which offer greater accuracy than progeny testing alone. sheepGenomics, dr forage says, is also investigating ‘functional biology’ to determine how genes work and what turns a gene ‘on’, or ‘off’. “sheepGenomics researchers have found that by treating a pregnant ewe at a specific time during pregnancy, we can affect the genes that influence follicle development in the lamb and ultimately influence its lifetime wool productivity and quality. “or in meat production, for example, a single mutation, known as callipyge, can cause a 40 per cent increase in the high-value loin and leg muscle. by studying callipyge animals we are learning which genes affect muscle development, and hope to develop a feed additive that could be given to sheep to switch these existing genes on.” the program is also looking at the genes associated with parasite resistance and, of these, which genes are turned off and on as a result of parasite infestations. proteins or chemicals produced when a gene is activated may offer potential as specific ‘biomarkers’. they could be used in simple on-farm tests to indicate if stock require treatment, as well as the most appropriate treatment to control parasites. More information: www.sheepgenomics.com A fAst-trAck Genetic roAdmAp AvAilAble Merino breeders wishing to boost sheep productivity and reduce susceptibility to flystrike can gain useful knowledge from the recently released report Merino Superior Sires 14. Executive officer of Australian Merino Sire Evaluation Association (AMSEA) Ben Swain says the AMSEA-published report, produced annually since 1994, enables breeders to compare hundreds of top sires evaluated at 14 sites across the major wool-growing regions in Australia. “Using Merino Superior Sires 14 and the more detailed individual site reports available at www.merinosuperiorsires.com.au, breeders can select for plainer, lower-wrinkle sheep as well as for higher productivity,” Ben says. “We have data on all the commercially important measured traits and up to 19 visual traits going back nearly 20 years. “This is a valuable resource for Merino breeders. It allows them to match sire selection to their specific breeding objectives.” The visually evaluated traits include body wrinkle, breech wrinkle, breech cover and crutch cover. Breeding and selecting plainer sheep with reduced wrinkle and crutch cover is a component of the wool industry’s drive to phase-out mulesing and satisfy retail demand for wool from unmulesed sheep. Recent research funded by AWI has confirmed that comparatively rapid change towards plainer sheep with significantly reduced wrinkle and breech cover is achievable and many growers are now pursuing this strategy. Ben, who is also a commercial woolgrower at Gunnedah, NSW, says many growers remain concerned that breeding and selecting for Ben Swain lower wrinkle and crutch cover simultaneously will select for lower productivity. “We now know from data accumulated through Merino Superior Sires (MSS) and from other sources that the correlation between fibre diameter and fleece weight, while negative, is not strong enough to prevent us from successfully selecting for decreased fibre diameter and increased fleece weight. “All the indications are that the correlation between wrinkle and fleece weight is less negative than that between fibre diameter and fleece weight, which means faster gains can be made in the right direction on both traits.” He says breeders can add reducing the incidence of flystrike to their breeding objectives when using MSS to identify suitable sires. “For example, you can select for productivity traits such as fleece weight, fibre diameter and staple strength at the same time as reduced wrinkle. This will get even easier with moves to develop across-flock Australian Sheep Breeding Values (ASBVs) for visual traits, as well as measured traits. “Adding another trait to your breeding objective may slow progress in existing traits, but it certainly won’t send you off-track chasing fads and should increase financial returns in the future.” Ben says genetic change takes time and he urges breeders to move on pursuing change today. MSS has traditionally been published in February, but the latest edition has been brought forward to provide a more timely source of independent information for breeders selecting sires for the 2009 joining season. More information: Merino Superior Sires 14 and the individual site reports can be accessed online at www.merinosuperiorsires.com.au ú ú
February March 2009
Oct - Nov 08