The detection of pigmented and medullated fibre in core samples of commercial sale lots from Merino ewes mated to Damara fat tail rams
Abstract
During the 1990’s a minority of Australian Merino wool producers diversified into fleece shedding breeds including the Damara fat tail breed. Some promoters of this breed had argued potential wool contamination was minimal or avoidable by farm management, but recent results/trials (Fleet et al. 2001) provide evidence to the contrary. In recognition of their concern about contamination from medullated and dark fibres, AWEX has introduced variations to clip preparation and marketing procedures, including the Woolclasser Development Program, that reinforce the risk of such wool contamination in certain crossbreeding situations. Indeed, they now require identification of affected lots in the marketplace (AWEX 2001).
There is no presale test or check currently available for dark or pigmented and medullated fibre. Diversification from entirely Merino production in Australia makes this deficiency more critical.
A trial was initiated by AWTA Ltd as a response to client inquiries to become involved in defining this contamination problem and in assessing the potential for presale testing using core samples of suspect wool lots. This report involves a limited survey of 25 sale lots to assess effects of crossbreeding Merino ewes to Damara fat tail rams as tested by 3 methods in 2 laboratories.
Core samples from bales of fleece wool from Merino ewes known to have reared Merino lambs (5 lots), or to have reared Damara crossbred lambs (14 lots), or to have been mated to Damara rams but failed to rear a lamb (6 lots), were tested for pigmented and for medullated fibres by 3 laboratory methods. The tests were performed at AWTA Ltd and SARDI. The wool from the 3 different farm management practices had significantly different (P<0.005) concentrations of pigmented and medullated fibre.
The ewes rearing the Merino lambs showed the lowest contamination, those rearing the Damara crossbred lambs showed the greatest contamination, and the remaining 6 lots showed intermediate concentrations of pigmented and medullated fibre. The 2 laboratories were not significantly different (P≥0.05) in their reported concentrations of medullated fibres and of the darkest (CSIRO darkness levels 6 to 8) pigmented fibres. However, for the pale-pigmented fibres (CSIRO darkness levels 4 and 5) and the total pigmented fibre concentration there were differences between the laboratories.
A trial has provided further evidence of wool contamination arising from crossbreeding Merinos with Damara fat tail rams. The trial has also highlighted limitations of the CSIRO Dark Fibre Detector for this purpose in terms of both its subjectivity and the operator time required for a test.
Citation
"The detection of pigmented and medullated fibre in core samples of commercial sale lots from Merino ewes mated to Damara fat tail rams", M.R. Fleet, T.J. Mahar and S.I. Denney, Report CTF 02, Commercial Technology Forum, IWTO, Nice Meeting, November 2001