Hormonal and wool fibre responses to maintenance or submaintenance feeding in Merino sheep with different staple strength

Abstract

This study examined whether sheep that produce sound wool have an ability to partition more nutrients to wool, during periods of under-nutrition. Groups of 12 low and 12 high staple strength sheep (SS) were fed to maintain or to lose 8% of liveweight over a 67-day period, fasted for 3-days and then re-fed above maintenance for 70 days. The SS groups had similar clean fleece weights, mean fibre diameters, SS, and staple lengths. Sub-maintenance feeding reduced fibre diameter at the point of break by 1.2 micron and SS by 16.1 N/ktex, compared to maintenance fed sheep. Over both feeding periods, cortisol and thyroxine concentrations were higher in the high SS group, while insulin concentration tended to be lower. It is concluded that SS groups differed in a number of metabolic hormones.