Genetics of wool colour in the South Australia selection demonstration flocks

A wide range of objectively measured and subjectively assessed characters were recorded in the South Australian Selection Demonstration Flocks between 1997 and 2005. These data provided an opportunity to study the genetics of wool colour and relationships with other traits, as part of a wider study by the Sheep CRC. In 2000, 2001 and 2002 clean wool colour was objectively measured by the Australian Wool Testing Authority on wool samples from 1,116 hogget rams. Clean colour was highly heritable (0.45). For assessed greasy colour the heritability was even higher (0.53), with a favourable negative genetic correlation (-0.38) between the two traits. There was a strong (0.57) positive genetic correlation between mean fibre diameter and clean wool colour and similarly a moderate negative genetic correlation with greasy wool colour. There was also a positive genetic correlation between clean colour and greasy fleece weight (0.34), dust penetration (0.35), and the standard deviation of fibre diameter (0.33). This indicates that selecting animals with heavier fleece weights tends to lead to progeny with wool that is more yellow in clean colour and that selecting animals with lower fibre diameter tends to lead to progeny that have whiter, more lustrous wool. The implications of these findings are discussed.M. L. Hebart and F. D. Brie