Response to selection in Australian Merino sheep. V.* Inheritance of abnormal staple crimp: Crimp abnormalities in groups of breeding ewes selected for high and low values of clean wool weight and its components

Abstract

Correlated responses in crimp abnormality in wool (i.e. irregularity of staple crimp frequency, to which the term "doggy" wool or "rough fleece" is applied when the crimp frequency is markedly reduced) are reported for two groups of Peppin Merino sheep selected for high clean wool weight, and for eight pairs of groups under selection for high and low values of the following single characters: clean wool weight per head, clean wool weight per unit area of skin, body weight, wrinkle score, fibre number per unit area of skin, fibre diameter, staple length, and percentage clean yield. In the first two groups the correlated responses in crimp abnormality were small and for practical purposes negligible. However. there appeared to be slight increases in crimp abnormality following changes in selection criteria, although this period coincided with adverse seasonal conditions. In the eight pairs of groups selected for single characters, correlated increases in crimp abnormality occurred in the groups selected for high clean wool weight per head, high and low fibre number per unit area of skin, high fibre diameter, and low percentage clean yield, and correlated decreases occurred in the groups selected for low clean wool weight per head, low fibre diameter, and high percentage clean yield. The responses were due mainly to the initial, intense selection of the foundation animals, and the responses to continuing selection were small. Environmental factors (year of fleece growth, maternal handicap, and lambing performance) did not have large effects on crimp abnormality. Crimp abnormality increased with age, and the rate of change was altered by selection in each of the single character groups in which correlated responses in crimp abnormality occurred, the responses being more pronounced at older ages.