Heritabilities and Genetic Correlations for Backfat and Age at 90 kg in Performance-Tested Pigs

Abstract

Performance test records for backfat depth and age at 90 kg made in breeder herds and a test station in Ontario between 1977 and 1984 were used for the study. After editing, numbers of records by breed were: 74,661 Yorkshire, 46,347 Landrace, 16,860 Duroc and 13,697 Hampshire. Numbers of litters were: 22,240 Yorkshire, 13,872 Landrace, 5,171 Duroc and 4,421 Hampshire. Numbers of sires represented were: 2,570 Yorkshire, 1,500 Landrace, 703 Duroc and 615 Hampshire. Variances and covariances were estimated by iterating on Henderson's new method. Analysis was within breed according to a model that included fixed herd (station)-year-season, sex, year of birth of sire and year of birth of dam effects and random sire, litter and error effects. Data were preadjusted for differences in weight at probe. Heritabilities were .44, .61, .44 and .40 for backfat and .36, .40, .27 and .46 for days to 90 kg for Yorkshire, Landrace, Duroc and Hampshire, respectively. Genetic correlations between backfat and days to 90 kg were –.11, –.05, –.17 and –.43 for Yorkshire, Landrace, Duroc and Hampshire. Respective phenotypic correlations were –.09, –.07, –.08 and –.08. Litter variances were large, particularly for days to 90 kg. Common environmental (c2) effects were .12, .10, .13 and .17 for backfat and .31, .31, .37 and .31 for days to 90 kg for Yorkshire, Landrace, Duroc and Hampshire.