Methods for estimating fibre length and diameter in wool staples

Present techniques to measure the fibre diameter and fibre length of indivi dual fibres are both time consuming and expensive, This has effectively res tricted the use of fibre length measurements in wool growth studies. This p aper describes and evaluates a number of techniques to measure fibre diamet er and fibre length. Sixteen fine wool Merino wethers at pasture were intra -dermally injected with S-35-cysteine and dyebanded on two occasions, 28 da ys apart. Fibre diameter was measured using image analysis and the Optical Fibre Diameter Analyser (OFDA). Fibre length was measured using a dyeband a nd a snippet technique, which both utilised image analysis. Mean fibre leng th and fibre length variations were also predicted using three prediction e quations based on staple characteristics including crimp frequency and OFDA fibre curvature measurements. Techniques that were developed to measure fi bre length growth rate and fibre diameter between dyebands were highly corr elated (r=0.81, P<0.05) with the S-35 estimates of fibre length. Fibre diam eter estimated by the snippet and the dyeband techniques were correlated (r =0.96, P<0.001) and the means did not differ (P>0.05). Mean fibre length wa s not significantly different (P>0.05) between the snippet and dyeband tech niques. The estimates of fibre length variation and fibre diameter variatio n were very different (r<0.47 and r<0.40 respectively) between the three te chniques. Fibre length predicted from staple characteristics was not: signi ficantly different (P>0.05) from, and highly correlated with, fibre length measured from the S-35 technique (r=0.85, P<0.001). Dyeband fibre length wa s best predicted by greasy staple length (r=0.91, P=0.0001) and snippet fib re length using prediction method three (r=0.69, =0.0042) which was estimat ed using a combination of the length of each crimp curve and the number of crimps between dyebands, Fibre length variation was not accurately measured nor predicted by the methods, described in this paper. These results an in dicate that mean fibre length growth of the fibres can be accurately measur ed and predicted without using the traditional autoradiographic techniques.