Battle against black fibres in Merino fleeces stepped up

29 Nov, 2008 05:38 AM
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The DNA-based Agouti test follows the identification by CSIRO Livestock Industries of the Agouti gene variants causing white and black sheep.
The DNA-based Agouti test follows the identification by CSIRO Livestock Industries of the Agouti gene variants causing white and black sheep.

Ram breeders are being urged to take part in a new initiative to help detect one of the genes responsible for recessive black pigmentation in sheep.

Australian Wool Innovation (AWI) says pigmented fibre is seen as a major contaminant of white fleece and pelts, which AWI says costs the sheep industry millions of dollars a year in lost revenue.

Studs are being sought to participate in the online survey, run by SheepGenomics (AWI and MLA), to provide data for the next stage of the development of an Agouti DNA test.

The DNA-based Agouti test follows the identification by CSIRO Livestock Industries (CLI) project leader Dr Belinda Norris of the Agouti gene variants causing white and black sheep.

This research project was co-funded by the former Sheep CRC, AWI and MLA through the SheepGenomics program.

CLI have applied this knowledge in the development of a DNA-based test capable of identifying the majority of Agouti carriers. During the last 12 months CLI researcher Dr John Henshall has shown that by using pedigree data as well as the test, the majority of white sheep that do not carry an Agouti pigment-causing allele can be distinguished from those that do.

“The Agouti gene is a significant discovery that will save the wool industry millions of dollars,” said CLI’s Dr Belinda Norris.

The Agouti test does not cover all forms of pigmented-fibre expression in sheep, as the other forms are controlled by different genetic mechanisms.

The test has undergone a first phase of validation in industry flocks and a commercialisation plan is being developed through SheepGenomics for delivery to industry.

Estimates of Agouti pigmentation frequency in the Australian sheep populations indicate that simple culling of pigmented sheep has little effect on eliminating these unwanted alleles from flocks.

While breeders have assiduously culled pigmented sheep out of the national flock for many decades, it is estimated that up to 15pc of the sheep population still carry the Agouti gene.

“This is not surprising given that the majority of pigmentation alleles are recessive and hence, white carrier animals don’t display the pigmented phenotype,” said Dr Graham Cam, AWI’s Project Manager Molecular Genetics.

“A highly prized ram unknowingly carrying the Agouti recessive allele can pass it on to 50pc of its progeny and produce pigmented offspring if mated to Agouti-carrier ewes in the breeding flock.

“Commercialising the Agouti test will provide woolgrowers and Merino breeders with an important tool for eliminating pigmented fibre from the clip,” said Dr Cam.

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