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A review of genetic parameters for visual traits in Australian Merino genetic resource flocks

Suzanne Mortimer


The visually assessed traits recorded in seven Australian Merino genetic resource flocks have been reviewed, together with published genetic parameters derived from these data sets. The visually assessed traits were categorised into traits which could be assessed using either standard scoring systems or non-standard scoring systems, as prescribed by the Australian Merino Sire Evaluation Association (AMSEA). For traits which could be assessed using standard scoring systems, genetic parameter estimates are available from the resource flocks for classer grade, wool character, fleece colour, fleece rot resistance, neck and body development, face cover and feet/legs (through front legs and back legs traits). For traits with non-standard scoring systems, genetic parameter estimates are available only for handle, nourishment (through wool condition traits), staple structure (through wool lock traits) and density. The visually assessed wool and conformation traits reviewed appear to be at least moderately heritable. The visually assessed traits generally have small or negligible genetic correlations with clean fleece weight, fibre diameter and body weight. However, the genetic parameters were often estimated with low accuracy and/or derived from data that were based on non-standard scoring systems. Accurate genetic parameter estimates, derived from data based on approved standard scoring systems, are needed to support the services and operations in genetic evaluation provided by Sheep Genetics Australia and AMSEA through Central Test Sire Evaluation. Attention needs to be given to wider implementation of approved standard scoring systems, which are practical to use and cover a greater range of visual traits. This will allow an expansion in the recording of visual traits and subsequent genetic parameter estimation based on the data generated. Important visually assessed traits then will be able to be incorporated into across flock genetic evaluation leading to improved genetic progress in the sheep industry.

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