Staple strength of fine, medium and strong wool Merino wethers under drought conditions
M. A. Friend A B D and G. E. Robards A CA Department of Wool and Animal Science, University of New South Wales, Sydney, NSW 2052, Australia.
B Current address: EH Graham Centre for Agricultural Innovation, Charles Sturt University, Wagga Wagga, NSW 2678, Australia.
C Current address: 10 Clarence St, Glenbrook, NSW 2773, Australia.
D Corresponding author. Email: mfriend@csu.edu.au
Australian Journal of Experimental Agriculture 46(9) 1123-1129 https://doi.org/10.1071/EA05085
Submitted: 16 March 2005 Accepted: 2 November 2005 Published: 4 August 2006
Abstract
Fine, medium and strong wool Merino wethers (n = 72, 4 years old) were grazed together on drought-affected pastures in a semi-arid environment. In order to examine the hypothesis that restricting liveweight gains at the break of drought would improve staple strength, sheep were allocated to restricted grazing in a 5-ha paddock (drought group), or unrestricted grazing in a 20-ha paddock (drought-break group) when it was judged that the drought had broken in the region. Wool staples from all sheep broke at a point coinciding with summer rainfall events before allocation to treatment groups, and staple strength did not differ between treatments. Medium wool sheep (22.0 ± 1.6 N/ktex) produced wool of lower (P<0.001) staple strength than fine (30.0 ± 1.6 N/ktex) or strong (30.2 ± 1.6 N/ktex) wool sheep. Restricting the measurement of staple strength to the period when treatments were applied revealed no effect of treatment on staple strength, despite the fact that wethers in the drought-break group experienced a greater (P<0.001) liveweight gain (6.62 ± 0.37 kg) after allocation to their treatment than those in the drought group (–3.24 ± 0.37 kg). Staple strength was most strongly correlated with coefficient of variation of fibre diameter (r = –0.65; P<0.001); a result that was observed for all strains and treatment groups. The results indicate that coefficient of variation of fibre diameter is correlated with staple strength regardless of strain, and that management strategies designed to limit fibre diameter variability during a drought need to be applied not only at the break of a drought.
Additional keywords: fibre diameter variation.
Acknowledgments
The authors wish to thank Messrs Noel Corliss and David Wilson for their care of the sheep and assistance with sampling. The authors also wish to thank Professor John James for his statistical advice and Mr David Petrie for his assistance in wool metrology. Part-funding for the work was supplied by Australian woolgrowers and the Federal Government as the senior author was in receipt of a postgraduate scholarship from the Australian Wool Research and Promotion Organisation (now Australian Wool Innovation).
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