Abstract

On one farm dipping sheep once or twice with zinc sulphate had no effect on the yellowness of wool at shearing. When data from this farm were combined with data reported earlier, the reduction in yellowness was linearly related to the yellowness of the control group (P = 0.091, 0.032 for dipped once or twice, respectively). On another farm, groups of 20 rising two-tooth New Zealand Halfbred ewes were treated in February by either dipping with zinc sulphate solution (2.45 g Zn/l) or dosing with a zinc bolus. Both treatments reduced the yellowness of belly wool at crutching (May) (Y-Z = 4.31, 2.13 and 1.87 for control, bolus and dipped sheep, respectively, P<0.01), but had no effect on the yellowness of the flank wool (Y-Z = -0.16, -0.27, -0.06). Zinc concentrations in clean wool (initial concentration = 78.5 mg/kg) were increased in all three groups at crutching but the differences were significant for the dipped group only (zinc concentrations = 160, 211, 340 mg/kg for control, bolus and dip, respectively, P<0.001). Thus, in some cases, increasing the concentrations of zinc in wool can reduce yellow discolorations at shearing. The effect will be greatest where wool from untreated sheep is yellowest. This could prove to be a useful method to improve wool quality on some farms.

TC, Reid, and RA Urquhart

Proceedings of the New Zealand Society of Animal Production, Volume 64, Hamilton, 277-281, 2004