Can dipping sheep with zinc sulphate reduce wool yellowing?
T.C. REID AND R.A. URQUHART
Wool Research Organisation of New Zealand (Inc.), Private Bag
4749, Christchurch, New Zealand
E-Mail:
NZSAP 2003 Abstract No. 40
Proceedings of the New Zealand Society of Animal Production
63: 164-168
On each of four farms, groups of ewes were either not dipped,
dipped once or dipped twice with zinc sulphate solution (20 g/l). Base
and challenge yellowness were determined on core wool samples collected
at shearing. Dipping with zinc sulphate increased the zinc concentration
of wool at shearing from 154 (range 77-321) to 421 (range 116-1140)
(dipped once) or 806 (range 143-1920) mg/kg (dipped twice). Zinc
sulphate dipping had no effect on the base yellowness of wool on three
farms, but significantly reduced wool base yellowness on the fourth farm
(Tristimulus (YZ) = 9.0 vs. 7.8 vs. 8.5 for control, dipped once and
dipped twice, respectively) (P<0.01). In the laboratory, wool samples
from all farms were significantly less yellow after challenge when
sprayed before challenge with zinc sulphate solution than when sprayed
with water (9.9 vs. 10.9; 7.1 vs. 10.0; 8.3 vs. 10.6; 11.3 vs. 13.1)
(P<0.001). There was a significant relationship (R2 =
83.4%, P<0.001) between the changes in zinc concentration resulting
from zinc dipping and the changes in yellowness of the wool with
challenge. These results indicate that dipping sheep with zinc may
reduce discoloration of greasy wool at shearing under environmental
conditions in which yellowing is maximised.
Keywords: NZSAPAB;
Crossbred wool; yellowing; zinc sulphate; challenge test;
propensity to yellow
Last Updated 8/07/2004
