Abstract

Mid-pregnancy shearing has been promoted as a technique to increase both lamb birth weight and survival in multiple-born lambs. Mid-pregnancy shearing has also been shown to increase dam wool quantity and quality and, in some instances, increase lamb growth rates until weaning. It has also been suggested that shearing of the dam during pregnancy results in a change in the lamb’s fleece characteristics. The aim of this study was to further investigate the effect of dam shearing treatment on lamb fleece characteristics. Thirty-one singleton and 29 twin-born lambs were born to either mid-pregnancy shorn or unshorn Romney ewes. At 6 months of age the lambs were midside sampled (to allow measurement of staple length (SL), washing yield, loose wool bulk, colour and mean fibre diameter (MFD)). A skin biopsy was taken from the midside to measure the ratio of secondary to primary follicles. The lambs were shorn three weeks later and a fleeceweight was obtained. Lambs born to shorn dams had a higher MFD (32.9 vs. 31.3mm, P<0.05) and had slightly whiter wool (0.1 vs. 0.3, P=0.07) than their counterparts born to unshorn ewes but did not differ for yield, SL or bulk. The higher MFD found in the lambs born to shorn ewes was associated with a decrease in the number of secondary follicles (P<0.05) without a significant decrease in the number of primary fibres. There was a significant interaction (P=0.05) between birth rank and shearing treatment on fleeceweight such that twin-born lambs born to shorn dams tended to have heavier fleeces (by 170g) than those born to unshorn dams, this relationship was not observed in singleton lambs. This study suggests that for singleton lambs, mid-pregnancy shearing of the dam will have no appreciable effect on wool value. However in twin-born lambs an increase in fleece weight may offset any decreased value due to higher MFD.

RG, Sherlock, PR Kenyon, and ST Morris

Proceedings of the New Zealand Society of Animal Production, Volume 62, Palmerston North, 57-60, 2002