The influence of specific farm management practices and environmental factors on the staple strength of merino wool

Wool of lowered staple strength (SS) is a major problem affecting the Australian wool industry. The problem has been estimated to cost the industry up to approximately ninety million dollars per year, with lowered SS being a major disadvantage for wool within the world textile market. The aim of this study was to investigate some specific farm management practices and environmental factors and to determine the influence of these on the SS of wool from merino sheep. A survey of additionally measured lines of wool from the region of the study (located in the Great Southern region of Western Australia) confirmed the importance of the autumn period in influencing SS and thus position of break (FOB). Subsequent trials investigated factors that might influence SS during autumn. Two experiments investigated the effects of different supplementary feeding regimes on the SS of wool from young merino sheep. Supplementary feeding with lupin grain, commencing at different times during the summer-autumn, did not result in consistent effects on SS. Different fodder crop grazing management regimes showed effects on the SS of wool from young merino sheep. For example, rationing access to an unharvested oat crop adversely affected the SS of wool from sheep at two sites. The fodder crop work also highlighted clinical alpha-tocopherol deficiency as a potential influence on SS. A field experiment designed to investigate the effect of alpha-tocopherol deficiency, failed to detect clinical disease in sheep at either of two sites. However, the results supported findings of other workers that subclinical alpha-tocopherol deficiency and associated myopathy is not likely to be a major influence on the SS of wool from sheep in the field. The impact of summer-autumn rainfall events on SS was investigated in four field experiments and one pen-based experiment. Field trials highlighted the importance of sheep dietary changes following a rainfall event on dry pasture in affecting SS. The pen trial and a trial with sheep protected by plastic coats at the time of the ‘break’ of the season also suggested that the rainfall itself and other climatic factors associated with it, were less significant as components of a summer-autumn rainfall event in affecting SS. A large-scale field experiment confirmed the significance of the ‘break’ of season as the critical period in determining SS and FOB. Factors associated with the dietary change experienced by sheep after wetting of the dry pasture on offer at this time require further investigation