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Beyond the Bale : Feb - Mar 08
The 19 visually assessed traits included in Visual Sheep Scores, each with a scoring scale of 1 to 5, are broken down as: ú wool-quality traits -- wool colour and character, fleece rot, dust penetration, staple weathering, staple structure, fibre pigmentation and non-fibre pigmentation; ú conformation traits -- jaw, legs/feet, shoulder/back, face cover and body wrinkle; and ú breech traits -- breech wrinkle, breech cover, dag and crutch cover. Substantial research has taken place through a number of organisations and groups that investigated the heritability of and correlation between visual traits and their relationships to production traits such as fleece weight, fibre diameter, growth rate and body weight, Dr Mortimer says. The information collected as a result of Visual Sheep Scores will be used to validate and enhance these studies. Dr Mortimer says heritability is high among many visually assessed traits, although fleece rot and front leg traits were only lowly heritable, and classer grade and back leg were moderately heritable. "Following that, most genetic correlations among the visual traits tended to be negligible to low in size but generally positive. However, there were exceptions, with a stronger relationship demonstrated between neck and body wrinkle scores, classer grade and wool handle, classer grade and wool colour, and wool handle and wool colour." In general, selection based on any of the visual traits will result in a favourable correlation or negligible response in the remaining traits, Dr Mortimer says. "There are real benefits to understanding these visual traits -- the dairy industry has been doing it for years. "It is important to consider the functionality aspects of the animal that enable it to produce, and keep producing in a sustainable way, and where integrating visual traits in a selection index plays its part." ú More information: Visual Sheep Scores is printed on waterproof paper and is available free from the AWI Helpline, 1800 070 099 sheep and wool producers with a set of standardised visual scores -- a new national language -- to consistently describe, record and class sheep for subjective traits. Dr Mortimer says the guide is a quick and simple visual assessment scoring system for the consistent description of important phenotypic traits of all breeds of sheep. It is designed to enable sheep breeders and classers to record and submit visual-score data and genetic information to Sheep Genetics, which has commenced development of across- flock Australian Sheep Breeding Values (ASBVs) for visually assessed traits. "We've needed information on visually assessed traits captured in a standard way so that we can evaluate animals and formulate breeding values to produce indexes that combine visual and objective measured traits," Dr Mortimer says. "From there we can tailor individual breeding and selection programs to meet various goals. There is huge scope for this." A particular benefit of the universal language that Visual Sheep Scores produces is when ram buyers are unable to inspect firsthand sale rams or semen sires, they can be provided with their Visual Sheep Scores performance to aid the selection process. "This guide is a real tool -- for classers, stud masters and commercial producers. It is a step forward for the industry and will provide a bridge between visual and objectively measured traits," Dr Mortimer adds. 7 GENETICS BEYOND THE BALE Bruce Lefroy: increasing recent emphasis on objective measurement has reduced genetic gains. Bruce Lefroy of 'Cranmore Park' says selection based on visual traits is crucial when breeding top-quality commercial sheep. The WA sheep breeder has been using objective measurement on the 5700-hectare 'Cranmore Park', 32 kilometres east of Moora, for many years, but says that recently visual assessment of sheep has again come to the fore. "In recent years, with increasing emphasis on objective measurement, I feel that the genetic gains have slowed," Bruce says. "Maybe it's because we're in a closed flock and we need to bring in a little variation, but I also think integrating visual traits into the selection process allows more scope for improvement." 'Cranmore Park' has five main breeding objectives. Bruce, who farms in partnership with sons Kristin and Andrew, aims to breed easy-care sheep, moving toward plain-bodied sheep with low fecal-egg counts and a sound structure. In selection he aims to reduce fibre diameter, increase clean fleece weight and reduce co-efficient of variation of fibre diameter, and to breed pre-potent rams that throw progeny with the same traits. Ultimately, 'Cranmore Park' is also looking for uniformity of wool type and fleece rot resistance, which are traits that form part of the Visual Sheep Scores guide. And for the past two years rams with bare breech areas have been specially selected. "These rams are the ultimate in easy-care -- with a bare breech and reduced risk of flystrike and other disease issues -- so we've made selection decisions based on the potential for this trait." Bruce says the attraction of a bare-breech 'Cranmore Park' Merino ram is that wool production has not been compromised in selection of bare breech.The cut on his bare breech rams is 3.01 kilograms clean per head averaged over the 38 rams with this trait. By comparison, in 2006 the wool produced by the rams had an average fibre diameter of 17.7 microns.The average fleece weight for 510 rams was 3.02 kilograms clean per head. The bare-breech trait is exciting for the industry, Bruce says. "Ultimately, sheep of this type will not require mulesing." 'Cranmore Park' is a member of MERINOSELECT. More information: www.cranmore.com.au Frame sheep typically weigh five kilograms above the average sheep in any age group, are sound in constitution and structure, as well as being robust and fertile. Frame sheep should exhibit at least three of the following five characteristics: softness, deep crimp, lustre, fibre bundles and rich white nourishment.Wool sheep are sound for frame, constitution and bone structure and should exhibit at least four out of the same five characteristics. "The aim of this corrective joining program is to eventually have all our sheep excellent in both body and wool and excelling in all characteristics. It is really about paying attention to detail." The total ewe flock of 2500 on 'Karori' is drawn on for replacement stud ewes. All hogget rams and ewes are side- sampled and fleece-weighed during shearing in September. Classing notes are made at shearing on length, handle, colour and style. Bellies are also graded.This information is used together with fibre diameter (FD) data, including co-efficient of variation, standard deviation of FD and curvature and fleece weight. Katrina says that since 1995 'Karori' has selected sheep carrying wools with genetically fine primary and secondary follicles with a high ratio of secondary to primary follicles, high fibre alignment and high follicle density. Over the past five years, 'Karori' has produced an average adult micron of 17.4 and an average hogget micron of 15.5. "We also look for small fibre bundles, good fibre length, rich white nourished and soft silky wool.We're really after that softness, in deeply crimping wools." 'Karori' aims to cut an average of 4.5 kilograms per adult ewe of 17.5 micron wool by 2010.The stud is a member of MERINOSELECT, the national genetic information and evaluation service for Merino ram breeders and commercial wool producers. More information: www.karori.com.au VISUAL ASSESSMENT HELPS GENETIC VARIATION PHOTO: CURRIE COMMUNICATIONS Score 1 Score 2 Score 3 Score 4 Score 5 Breech Wrinkle -- Lambs Score 1 Score 2 Score 3 Score 4 Score 5 Wool colour Jaw Score 1 Score 3 Score 5 The new Visual Sheep Scores guide covers wool traits (colour for example), breech traits (for example, wrinkle) and conformation traits (for example, jaw).
Feb - Mar 08 Supplement
Apr - May 08