PREDICTING THE RISK OF DARK FIBER CONTAMINATION IN SALE LOTS

Dark fibre contamination remains an important issue for Australian woo l although concern over other contaminants in tops, such as pack mater ial, bale twine and vegetable matter particles, has often overshadowed the issue of dark fibres that originate on sheep. This paper reviews past and current research initiated by CSIRO that deals with the dark fibre problem arising from urine stained and pigmented fibre contamina tion. Australian merino fleece wool is relatively free from melanin pi gmented and urine induced coloured fibre contamination and, as such, i s in demand for white and pastel end uses. There is a need, however, f or a method of quantifying the potential risk from these contaminants in the end product before the greasy wool is sold. It has been demonst rated that sampling for a discrete contaminant such as a few staples o f pigmented or urine-stained wool in a bale is not practical. Therefor e, an alternative approach is to utilise information that predicts the likelihood of dark fibre contamination being present on the sheep at shearing and the relative potential for such contamination in subseque nt sale lots. Results from various studies on consignments, sale lots and experiments in the shearing shed are considered in relation to :- guidelines that can now be given to enable the trade to obtain wool wi th a low risk of dark fibre contamination, the implications for indust ry quality assurance systems and the likelihood of devising a commerci ally robust and reliable predictive scheme for levels of contamination in sale lots and in mill consignments.