Merino wool contamination from rearing of Damara crossbred lambs

Abstract

Recent importations and promotion of Damara sheep has raised concerns and debate about potential for Merino wool contamination. This project examined Merino ewe wool contamination arising from the mating of Damara rams and rearing of Damara crossbred lambs. Shirley-blended core samples from 3 commercial greasy wool sale lots known to involve Merino ewes shorn with Damara crossbred lambs at foot (2 lots), or shorn 3 weeks after weaning, were assessed. Contaminant fibres were above commercial expectations for Merino wool and present in every core sample measured. There was no significant difference found between these sale lots. From an experimental flock, composites of fleece samples were carded and the effects of mating or rearing alone assessed. No detectable increase of pigmented or heavily medullated fibres, above very low background levels, were detected among the Merino ewes mated to Damara rams (1 ram per 65 ewes). However, high concentrations of contaminant fibres were found in the Merino ewe wool at weaning of their Damara crossbred lambs and also 3.5 months after weaning; with reduced levels post-weaning. The management strategy of restricting wool exposure to mating effects alone may offer advantage but delaying shearing of ewes after weaning to reduce the contaminant fibre burden was, in this case, not sufficient to overcome potential concerns for wool processing. However, in view of the many potential contributing factors, actual contamination may vary widely between cases and require the advancement of presale measurement to gain buyer confidence and accurate appraisals.