Effect of fleece weight selection on reproduction, live weight and wool characteristics in mature Romney ewes

This paper presents the analysis of 3525 production records of mixed age Romney ewes in a fleece weight selected (HF) or random control (RC) flock over 11 years. HF ewes were significantly (P < 0.001) heavier than RC ewes for autumn live weight (8%), winter live weight (9%), summer live weight (7%), greasy fleece weight (20%) and clean fleece weight (19%). Small but significant (P < 0.01) flock differences were also found for wool fibre diameter and wool yellowness. HF flock fleeces were coarser (1.0 m) and more yellow (0.8 unit) than RC fleeces. The HF flock was significantly (P < 0.01) higher than RC for ovulation rate (1.80 vs. 1.73 SED 0.03), number of lambs born/ewes lambed (1.63 vs. 1.56 SED 0.02), and number of multiple births/ewes lambed (60% vs. 54% SED 2%), but lower (P < 0.01) for number of lambs weaned/lambs born (0.84 vs. 0.88 SED 0.01). The results indicate that single trait selection for fleece weight enhances greasy and clean fleece weights, live weight and ovulation rate, with an associated increase in fibre diameter and yellowness of their fleeces