Effect of fitting sheep covers and injection of a mineral supplement on the brightness, clean colour and photostability of wool grown by grazing Merino sheep

Abstract

Wethers sourced from a Merino genetic resource flock, selected on the basis of their measured wool clean colour at 2 years of age, were stratified on the basis of clean colour and allocated to one of four treatment groups in a 2 × 2 factorial design. The aim was to investigate the effect of coating the fleece and administration of a commercial mineral supplement on brightness, clean colour and photostability over a 12-month period when run on the Central Tablelands of New South Wales. Coating the fleece significantly improved both the brightness and clean colour of the fleece (P<0.001, by 4 and 0.5 T units, respectively), but had no effect on the photostability of the two traits. The mineral supplement had no significant impact on the colour or photostability traits and there was no evidence of an interaction between coating the fleece and the mineral supplement. Although the improvements in brightness and colour arising from coating the fleece complemented the predicted responses to genetic selection for these two traits, the combined effect would not be sufficient to replace the routine use of oxidative bleaching during processing.