Abstract

Data from Yorkshire, Landrace, Hampshire and Duroc swine born between 1976 and 1983 in Ontario and raised either on farm or at central test stations were used in a program for prediction of breeding values for growth rate (days to 90 kg) and backfat thickness (mm). The single trait within breed model included fixed herd-year-season (hys), random litter within hys, random pig within litter and residual effects. Year-seasons were based on date of birth, with seasons being (1) January to June and (2) July to December. Relationships among pigs provided genetic ties among herds. The number of mixed model equations was decreased by use of a reduced animal model and by absorption of unneeded hys and litter equations. Equations were solved iteratively by successive over-relaxation with a relaxation factor of 1.25. Equations were updated with new data, rather than regenerating all equations each time evaluations were computed. Information available to producers include predicted breeding values (PBV) of sires and dams in current use, average herd genetic and management values, and within herd genetic trend. Possible use of the program to provide PBV of pigs as they are recorded is discussed.