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Beyond the Bale : Feb - Mar 08
SELECTION SEEKS GOOD ALL-ROUNDERS Katrina says a universal language, like that which has been developed as the Visual Sheep Scores guide, would be of enormous benefit to those trading sheep sight-unseen, as well as those using artificial insemination. "We obviously work to our own visual-trait assessment system, but if we could talk with others in the industry and have them understand exactly what we mean, that would be a huge benefit when it comes to buying and selling sheep." Located in a high-rainfall zone (950 millimetres), Katrina says a long-term priority for the stud has been to eliminate fleece rot. "We've bred our sheep to withstand these wet conditions, and through visual assessment and subsequent selection pressure our sheep are now highly resistant to fleece rot." New genetic research has shown that commercial and stud sheep breeders can boost productivity by up to 30 per cent by incorporating visual assessment criteria into their breeding selection indexes. The research takes a major step toward measuring the economic benefits of selection for structural, conformation and wool-quality traits on meat and wool production. It also highlights the relationships between traits, and the impact of targeted selection strategies on individual traits. Trangie-based NSW Department of Primary Industries livestock research officer Dr Sue Mortimer says real benefit can come from including visual traits with measured traits using an index that ranks animals on how well they meet a particular breeding objective. "It allows greater and more effective use of variation in selection differential for traits of economic value," Dr Mortimer says. "At present, 30 per cent -- or more -- of the effective selection differential is assumed to be directed to visual traits independent of the measured traits." Dr Mortimer says effective selection differential is an indicator of superior performance in selected animals. The selection differential is the variation in the trait between the selected animals and the average of all animals before selection. "By using both visual and measured traits in their selection indexes, sheep breeders should be able to implement more efficient selection strategies, and therefore make greater genetic progress." Dr Mortimer has conducted the research project, funded by AWI, which used data on visually assessed traits collected from the QPLU$ flock at Trangie, as well as Merino Selection Demonstration Flocks managed by SARDI, the CSIRO Fine Wool Project flock and Central Test Sire Evaluation flocks managed by the Australian Merino Sire Evaluation Association (AMSEA). The project demonstrated that many visually assessed traits can be passed from one generation to the next, and began to investigate genetic correlation -- that is, the effect of selecting for one trait and its impact on other traits -- between some visual and production traits. These research findings have led to Dr Mortimer supporting the Visual Sheep Scores guide, launched last month. The first-of-its-kind pocket guide, developed by AWI and Meat and Livestock Australia, in consultation with industry, provides GENETIC BOOST from joining visual and measured traits A new manual outlines 19 visually assessed traits -- wool quality, conformation and breech traits -- that, when used with objectively measured traits, can help increase genetic progress 6GENETICS BEYOND THE BALE Katrina Blomfield: a firm believer in the benefits of visual trait assessment. PHOTO: CURRIE COMMUNICATIONS Combining visual-trait assessment with objective measurement is the key to genetic gain, according to 'Karori' Merino stud's principal, Katrina Blomfield, from Walcha, NSW. Consistently at the top of the superfine Merino wool production game, Katrina says 'Karori' has been lining its own visual-traits assessments up against objective measurements in its selection strategies for years. "Selection decisions are made on both objective and visual assessment data," says Katrina, who runs the stud in the southern New England region with husband Rob. "It can be a complicated process, but it allows us to tailor our selection and ensure we're achieving what is needed." A firm believer in the benefits of visual trait assessment, Katrina classes all sheep on 'Karori' and emphasises the need for quality in conformation as well as wool. "We believe in good-sized, plain-body sheep, with good fleece weights for micron, and soft-handling wool. For many of these attributes, visual measurement is the only way to go." Katrina says all sheep are classed annually in a classing box, body weighed and selected for good hoof and bone structure and constitution, loose skin, soft and free of wrinkle, high fertility, clean open faces with no pigmentation, high-quality bellies, resistance to flystrike and fleece rot, and resistance to worms. "We use these observations to class each sheep as a 'frame' or a 'wool' sheep, and a corrective joining program is used that cross-breeds between the two groups of attributes." Visual Sheep Scores
Feb - Mar 08 Supplement
Apr - May 08