A sixteen year selection trial in a flock of Perendale sheep selected for either increased (H line) or decreased (L line) wool bulk at yearling (hogget) shearing, was undertaken at Whatawhata, and later Winchmore Research Stations. A total of 2,620 progeny sired by 172 rams joined in single sire matings were measured, with data from an additional 664 fleeces providing direct information on base flock characteristics. A restricted maximum likelihood (REML) animal model adjusting for fixed effects of year, sex, birth date and birth/weaning rank was fitted to the data. Heritability estimates ± standard errors for each of the measured characteristics were; core wool bulk (0.57 ± 0.03), pre-shear live weight (0.35 ± 0.04), greasy fleece weight (0.44 ± 0.04), washing yield (0.42 ± 0.03), clean fleece weight (0.45 ± 0.03), staple length (0.54 ± 0.03), total crimps (0.38 ± 0.03), crimp frequency (0.46 ± 0.03), mean fibre diameter (0.62 ± 0.04), fibre diameter variation (0.58 ± 0.04) and mean fibre curvature (0.67 ± 0.04). At the end of the trial, line divergence (H – L) in core wool bulk and fibre curvature amounted to 2.5 phenotypic standard deviation units. It was associated with a positive divergence in crimp frequency and a negative divergence in staple length, washing yield and clean fleece weight of +2.1, -1.7, -1.4 and –0.8 standard deviation units respectively, and lesser changes in other traits.
Proceedings of the New Zealand Society of Animal Production, Volume 67, Wanaka, 180-186, 2007
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