Effect of wither malformation on the pre-disposition of sheep to fleece rot and body strike

Abstract

The presence of the conformational fault 'pinch' (narrow depression over the 4th-6th ribs) was examined in relation to fleece rot susceptibility. A field study involving 189 Merino ewes showed that the identification of the fault (incidence was 11%) by 4 independent observers was highly repeatable. Fleeces on the pinch site showed a disorderly staple arrangement with a higher incidence of tangled and narrow staples compared with unaffected sheep. The pinch fault appeared to be associated with excessively sloping front pasterns ( lt; 45¦ from the ground) compared with unaffected sheep (about 70¦). In 2 experiments, it was shown that the 'pinch' fault was associated with a higher incidence of fleece rot and a higher level of moisture penetration and retention in the fleece during fleece rot induction. Staple crimp, staple density and fibre diameter (mean and variability) were associated with the wetting and drying characteristics of the fleece but not specifically with the pinch fault. It is suggested that the mechanical movement of the fleece at the pinch site was responsible for the increased moisture penetration which, in turn, increased the chance of development of fleece rot and fly strike.