STUDIES ON WESTERN-AUSTRALIAN MERINO SHEEP .2. GENETIC AND PHENOTYPICPARAMETER ESTIMATES FOR OBJECTIVELY MEASURED TRAITS ON RAM AND EWE HOGGETS USING DIFFERENT MODEL TYPES

Data from a Western Australian experimental flock of Merino sheep were used to estimate genetic and phenotypic parameters for clean fleece w eight (CFW), greasy fleece weight (GFW), average fibre diameter (FD), and clean yield (Y) from hogget fleeces as well as liveweights at birt h (BWT), weaning (3WT), 8-9 months (8WT), 11-12 months (11WT) and 14-1 5 months (14WT) of age. The estimates were derived for male and female hoggets using restricted maximum likelihood REML. Simple models were fitted in which most environmental effects were omitted for comparison with results from models containing all recorded significant environm ental effects. There were no significant differences amongst heritabil ity estimates between models or sexes. Genetic correlations were calcu lated between sexes for each trait, with none being significantly diff erent to unity. Ranges of heritability estimates across models and sex es were: GFW, 0.30-0.42; CFW, 0.26-0.44; Y, 0.46-0.59; FD, 0.47-0.59; BWT, 0.16-0.33; 3WT, 0.32-0.39; 8WT, 0.22-0.36; 11WT, 0.27-0.44; 14WT, 0.27-0.50. Estimates of genetic and phenotypic correlations were in r easonable agreement with other literature values. As with the heritabi lity estimates, the model fitted did not result in important differenc es in either genetic or phenotypic correlations.