Skin folds and Merino breeding. 9. Efficiency of conversion of food to wool

Abstract

This paper reports a study of the efficiency of wool production, liveweight change and ad libitum intake of 60 hogget ewes from flocks selected for 15 years for skin wrinkle (Folds Plus), against skin wrinkle (Folds Minus) and randomly selected as a control (Random). Initially, under restricted feeding ewes from each genetic flock consumed 594, 750, 951 or 1097 g DM day-1 of a lucerne pellet ration. The mean efficiency of clean wool production of Folds Minus ewes (8.47 g CW/kg D.M.I.) was less (P < 0.05) than that of either Random (9.38) or Folds Plus (10.18) ewes, which did not differ significantly. During the following ad libitum feeding period, the Folds Minus ewes again produced less wool than either of the other groups and their wool production was less efficient even though they consumed significantly less feed than either Random or Folds Plus ewes. The significant difference in intake between Random and Folds Minus ewes remained when the n takes were corrected for liveweight (kg), metabolic body size (kg0.73) or surface area based on liveweight alone (kg0.67). However, when fold score (FS) was included in the surface area estimate as LW0.67 + FS0.2 the intake difference between flocks became very small. The experimental results and components analyses of the pre- and post-shearing data showed that selection for skin fold had not changed wool growth rate or efficiency of wool production, but had reduced staple length. On the other hand, the lower wool production of Folds Minus ewes was due to both reduced surface area and lower wool production per unit area.