Production of genetically identical swine: Uses for families with reduced phenotypic variation

Recent advances in reproductive technology hold promise for future production of nearly unlimited numbers of swine with identical genotypes through the use of nuclear transfer. Potential benefits of use of these animals in the swine industry and in research are examined in the present study. Variability of litter size, days to slaughter and backfat thickness are predicted for clones, full-siblings and unrelated animals. One hundred simulation runs of 100 unrelated animals and 25 families of 4 full-siblings and clones were completed for each trait. Expected phenotypic standard deviations were 2.5 pigs for litter size, 12 d for days to slaughter and 2 mm for backfat thickness. Between family variances were expected to include 50% additive genetic variance, 25% dominance variance and 100% common environmental variance for full-siblings and 100% of all 3 components for clones. Substantial advantages of clones over unrelated animals and smaller advantages of clones over full-siblings were found for variability of days to slaughter and backfat thickness, but little difference was found for litter size. Ratios of error mean squares from analyses of variance suggest that use of clones rather than unrelated animals could reduce the number of animals needed for experiments by 67 and 65% for days to slaughter and backfat thickness, respectively, but only by 12% for litter size. These results suggest that the first use of cloned swine would be to reduce the numbers of research animals needed for intensive studies.