Contamination of white wool by melanin-pigmented fibres when pigmented and white sheep graze together.

Abstract

Various densities of black sheep (0, 2%, 9.5%, 21.4% and 50%) were run with white sheep for a period of 10 weeks. The groups were yarded on average once weekly. The number and lengths of melanin-pigmented wool and kemp fibres were measured in carded wool samples from the white fleeces. All groups containing black sheep produced white wool with higher levels of pigmented fibres (an increase of 8- to 64-fold) than the control group (P< 0.05). The extent of contamination of white wool by pigmented fibres increased with the density of black sheep. Both pigmented wool and pigmented kemp fibres occurred frequently in the contaminated wool samples and the fibres mainly had lengths less than 10 mm. The results provide evidence of the risks involved in the practice of including pigmented sheep in white sheep flocks.