Skins were compared from 2 groups of 18-month-old Cheviot, Drysdale, and Romney wethers reared under hill country conditions, and offered initial pasture allowances per animal after weaning of either 1.5 or 3.0 kg DWday increasing progressively to 2.0 or 4.0 kg DWday at slaughter. Cheviot skins were more suited to wool-on leather production, whereas Drysdale and Romney pelts were more suited to garment leather production. Cheviot leathers were more resistant to tearing, with a stronger more extensible grain layer, more pinhole, more mottle, and less double-hiding than the other breeds. Drysdale leathers had most cockle, and Romney leathers least pinhole. Improved feeding increased weight, area, and thickness of the leather, occurrence of mottle and neck, resistance to tearing, and the strength and extensibility of the grain layer.
A flock of New Zealand Wiltshire sheep was divided into two lines and selected for increased greasy fleece weight or decreased greasy fleece weight as yearlings. Wiltshires shed their fleece annually, and although these yearlings may have expressed shedding as lambs in the preceding summer, they were shorn in autumn at 5 months and again in spring at 12 months of age to determine fleece weight before the subsequent shedding. A rapid separation in fleece weight was observed within 8 years, with ewe (0.89 kg) and ram yearlings (0.92 kg) selected for increased fleece weight producing significantly more wool (P < 0.001) than ewe (0.43 kg) or ram yearlings (0.39 kg) from the line selected for decreased fleece weight. There was no significant difference between sexes, and the sex × line interaction was not significant. Clearly this was very low wool production, but fleece weight was heritable (h2 = 0.57 ± 0.04).
Shedding was scored from 0 (not shed) to 5 (completely shed) for all animals (n = 2505 records) and was found to be heritable in December (h2 = 0.39 ± 0.04) and again in January (h2 = 0.52 ± 0.05), but less so in September at shearing (h2 = 0.24 ± 0.03). Fleece weight in spring was negatively correlated with shedding score in January, both phenotypically (–0.52 ± 0.02) and genetically (–0.81 ± 0.04). Selecting yearlings for low fleece weight developed a shedding sheep with negligible fleece, which may not require shearing. Selecting for shedding of lambs in January would likely achieve a similar outcome.
An experiment was carried out to study direct and indirect responses to selection in Romney sheep. There were two selection lines, one selected for greasy fleece weight (GFW) and the other for liveweight (LW), maintained alongside a control line (CO). Data from lambs born in 1967-90 were analysed to quantify the correlated responses to selection. By 1990, there had been an average of nine generations of selection with an average generation interval of 2.7 years. The correlated responses analysed included yearling and ewe greasy and clean fleece weights, washing yield, yearling and ewe fleece quality traits (staple length, mean fibre diameter, fibre diameter variation, loose wool bulk, Commission Internationale de l'Eclairange (CIE) Y value (brightness) and CIE Y-Z value (yellowness)), birth weight, weaning weight, yearling liveweight, ewe pre-mating weight, and ewe reproductive rate (fertility, litter size, weaning percentage, and lamb survival). Correlated responses were estimated as the deviation of selection lines from the CO line, and genetic correlations were obtained by restricted maximum likelihood techniques. Direct responses measured in the GFW and LW yearlings were 1.7 and 1.2% per year, respectively. Correlated annual responses were 0.7% in yearling liveweight in the GFW line and 0.2% in yearling fleece weight in the LW line. Corresponding annual changes in ewe performance were 1.5% in greasy fleece weight and 0.5% in pre-mating weight in the GFW line, and 0.0 and 1.2% respectively in the LW line. Mean fibre diameter increased in yearlings and ewes of the GFW line, but did not change in the LW line. There were small but significant increases in staple length in both lines. Loose wool bulk among GFW yearlings was reduced by 0.12% per year but did not change significantly in ewes. Yearlings and ewes of the LW line both showed an increase in bulk (0.15 and 0.43%, respectively). Relative to the CO flock, CIE Y-Z among yearlings increased significantly by 1.35% per annum and 0.25% per annum in the GFW and LW flocks respectively. Among ewes it increased in the GFW line whereas the opposite occurred in the LW line. There was no significant change in percentage ewes lambing as a result of GFW or LW selection. Litter size increased and lamb survival to weaning decreased significantly, but there was a net increase per year in lambs weaned per ewe lambing (0.27% per year for the GFW line and 0.48% per year for the LW line).
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