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.

RMW, Sumner, JN Clarke, and NG Cullen

Proceedings of the New Zealand Society of Animal Production, Volume 67, Wanaka, 180-186, 2007
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