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Abstract
Genetic parameters for weaning and yearling (14-15 months) traits were estimated using 3313 half-sib records from 62 sires and 1720 daughter-dam pairs. The estimates of heritability by paternal half-sib and daughter-dam regression analyses were respectively: weaning weight (WW) 0.20 and 0.16, hogget body weight (BW) 0.27 and 0.44, greasy fleece weight (FW) 0.32 and 0.30, quality number (ON) 0.26 and 0.13, fibre diameter (FD) 0.54 and 0.47, staple length (SL) 0.49 and 0.35, and fleece character (FC) 0.23 and 0.23. Estimates of genetic correlations were in the following ranges: Medium negative (−0.4 to −0.6) BW × FC, ON × SL; Low negative (−0.2 to −0.4) WW × ON, FD × FC, ON × FW, ON × FD; Low positive (0.2 to 0.4) BW × WW, BW × ON, SL × FC; Medium positive (0.4 to 0.6) FW × FD, FW × FC; High positive (0.6 and over) FW × SL.
Phenotypic correlations generally agreed with the genetic correlations. Important exceptions were BW × FW and BW × FD. Among the environmental factors studied, age-of-dam and rearing-rank effects on the wool traits were generally small. These factors had a marked influence on weaning weight and hogget body weight. At weaning, singles were 4.2 kg heavier than twins, and at 14 months this difference had been reduced to 2.1 kg. The progeny of 2- year-old dams were 1.44 kg lighter at weaning and 1.11 kg lighter at 14 months than animals reared by mature dams.