Abstract:
This study aimed to improve the prediction of genetic differences in staple strength (SS) by defining factors that affect differences in SS among progeny groups in 2 sire test trials. The SS was related to mean fibre diameter (FD) and the standard deviation in fibre diameter (SDfd) in both trials (P<0.001), and to staple length in one trial. Sire contributed independently to SS in both trials (P<0.001). Detailed measurements on wools from Flock 2 showed that the relative importance of different components of SS differed among sires (P<0.01); for example, FD had a greater effect on SS in animals with a relatively low SDfd. An equation involving SDfd and FD accounted for only 26% of the variation in SS, but this was increased to 50% of the variation in SS by also incorporating the proportion of fibres greater than 30 m and the amount of unevenness in FD (blobs) measured on clean staples with an OFDA2000. If these findings are robust, they offer a means by which breeders who wish to avoid the expenseof direct measurement of SS may improve the efficiency of their selection for this characteristic.