Levels of dark fibre contamination were determined on 49 core samples of scoured wool, representing 30 export consignments of crossbred wool received from three exporting companies. The concentrations of dark fibres ranged from 0 to over 3300/kg. Only four consignments contained less than 100 dark fibres/kg, twelve contained less than 500/kg, while four contained more than 2000/kg. The two highest levels of contamination (>2300/kg) were found in consignments containing lambs wool, although other consignments with lambs wool contained relatively low levels (<500/kg). Some fleece blends also contained relatively high levels of contamination (>1000/kg). All consignments containing down fleece wool were contaminated with dark fibres to levels which were highly correlated with the proportions of down fleece wool. Overall, 53% (range 7-100%) of the dark fibres found were melanin pigmented, 14 % (range 4-33%) were urine stained and 25% (range 5-63%) were of foreign origin. The results indicate that there is a considerable degree of dark fibre contamination in some export consignments of New Zealand crossbred wool. The one single factor consistently associated with increased levels of contamination was the presence of down fleece wool in the blend. The presence of lambs wool was associated with high levels of contamination in some consignments, but not in others. This suggests that only some lines of lambs wool contain high levels of dark fibre contamination.

TC, Reid, and RA Urquhart

Proceedings of the New Zealand Society of Animal Production, Volume 64, Hamilton, 282-285, 2004
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