The estimation of fibre diameter profile characteristics using reduced profiling techniques

Alternative snippet sampling methods for rapidly estimating fibre diameter profiles (FDPs) are investigated in this paper using sheep grazing in two e nvironments. FDPs were measured using staples from 40 Merino ewes from Chis wick in a temperate environment (n=20) and Bakers Hill in a Mediterranean e nvironment (n=20). These ewes were the progeny of two sires within each of two bloodlines grazed at the two environments. Technique 1 was a simple red uced profiling technique, which generated profiles based on a subset of the original snippets. The FDP characteristics of maximum fibre diameter (Max) , minimum fibre diameter (Min), difference between the maximum and minimum fibre diameter (Diff), fibre diameter variation along the profile (AstCV), average fibre diameter of the FDP (Profmean) and position of the Max estima ted by technique I were highly correlated with those calculated from the fu ll profile (r > 0.96). The correlations for the positions of Min were high( r> 0.83) while the correlations for the rates of fibre diameter change betw een the Max and the Min were lower, ranging from 0.65 to 0.90. This techniq ue did not allow for the shape of the FDP and as a result often calculated a rate of change that was not significantly related to the original FDP. A profile prediction technique was evaluated which utilised cubic spline fu nctions to generate predicted profiles based on reduced profiles. This tech nique utilised more FDP characteristics and allowed for the calculation of two rates of fibre diameter change for each FDP. The actual fibre diameter values of the predicted profiles were all not significantly different (P>0. 05) and highly correlated (r> 0.91) with the original full profile at all l evels of snippet inclusion. The measures of absolute fibre diameter and alo ng-staple variation in fibre diameter within the FDP were accurately estima ted (r> 0.80) using only 1 in 10 snippets ton average approximately 13% of original snippets). Using approximately 27% of the original snippets all FD P characteristics can be estimated with acceptable accuracy (r > 0.80). Env ironment, bloodline and sire had significant effects on most FDP characteri stics. These differences did not adversely affect the accuracy of the reduc ed profiling procedure.