GENETIC AND PHENOTYPIC PARAMETERS FOR DAILY GAIN AND BODY WEIGHTS IN SUFFOLK LAMBS

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Abstract
Body weights of 19 400 Suffolk lambs from the Federal-Provincial Canadian Record of Performance program were studied. The paternal half-sib estimate of heritability for daily gain from 50 to 100 days of age was 0.47 ± 0.04. The corresponding estimates for lamb weights at 50 and 100 days of age were 0.46 ± 0.04 and 0.43 ± 0.04, respectively. The moderate levels of heritability and the intermediate (16–25%) coefficient of variation in the Suffolk breed confirm that selection for daily gain and body weights would result in genetic response. Estimates of genetic and phenotypic correlations among daily gain from 50 to 100 days of age and 100-day lamb weight were 0.80 ± 0.02 and 0.73, respectively. Corresponding correlations among lamb weights at 50 and 100 days were 0.89 ± 0.02 and 0.76. Selection for daily gain from 50 to 100 days of age does not offer any advantage over selection based on lamb weight at 100 days when lamb weight at that age is the response criterion. Similarity in the estimates of genetic and phenotypic parameters from 1980 to 1983 indicates the stability of the estimates and their usefulness in selection indexes and predicting breeding values for sheep in the Canadian performance testing program. Key words: Suffolk, lamb weights, heritabilities, genetic correlations