Speaker Notes

Written by: Dr. Tony Schlink, CSIRO Animal Production.

Adapted from Schlink, A.C. and Dollin, A.E. (1995) Wool Technology and Sheep Breeding 43, 268-284.

This graph shows the relationship between staple strength and the proportion of shed fibres in the staple. There is a an exponential decline as shedding decrease, staple strength increases. If there are more that 10% shed fibres in the staple, the staples would be considered tender, however, if there are less than 10% shed fibres in the staple, staple strength can vary from rotten to very sound. This suggests that shedding does affect staple strength but it is not the only cause. Changes in fibre diameter along the staple is usually the major component of staple strength change.

In Merino sheep, the incidence of shedding under normal grazing conditions is generally low (<1%) and linked more to seasonal changes in feed, physiological condition and stress. However, Schlink and Dollin (1995) found the incidence to range from 0 to 30% in adult Merino wethers in the Mediterranean environment of WA, under conditions resulting in body weight loss during late summer. Those wethers with high levels of shed fibres produced the lowest staple strengths. But note that at levels <5% shed fibres, staple strength still ranged from as low as 20 to as high as 60 N/ktex. So obviously other causal factors are involved.

(adapted from Crook B, 1999, Wool Production, CRC for Premium Quality Wool Lecture Series).