The repeatability of textural wool handle

Abstract

Merino breeders use textural greasy wool handle in ram buying and breeding decisions. The effectiveness of the current wool handle scoring system has not been objectively evaluated. The assessor repeatability of textural wool handle was quantified using three different methods of assessment (on the live animal, as a greasy wool mid-side sample, and as a clean (scoured) wool mid-side sample). The aim of the study was to determine which method of assessment is the most repeatable. Three separately defined repeatability estimates were calculated based on knowledge about the operator. The first estimate was based on the assessor repeatability from the operators used in this study. The second estimate was calculated using replicate values obtained from the same random assessor and the third estimate was based on two results from independent random assessors. The results demonstrated that the assessor repeatability was the greatest when handle was assessed on the clean wool mid-side method, followed by the greasy wool mid-side assessment, and least in the live-animal assessment. However, there was significant variation in the repeatability estimates between the four assessors used in the study. Accounting for fixed effects such as sex, sire group, birth type and rearing type, decreased the variation observed and thus had a negative impact on the assessor repeatability of textural wool handle. The results in this study indicate that non-wool constituents negatively impact on the ability of an assessor to consistently assign a score for textual handle in the greasy wool mid-side method. It is likely that the added cost and time required for scouring to assess handle in the clean state may not be economically viable in most situations. However, the increase in repeatability by assessing handle in greasy wool mid-side method compared with the live-animal assessment indicates that sheep producers should use this strategy when evaluating the trait on-farm.