Phenotypic and Genetic Change for Lean Growth Rate and its Components in U.S. Landrace Pigs
Records on 65,536 Landrace pigs collected between 1985 and 1999 in herds on the National Swine Registry STAGES program were used to estimate genetic change in lean growth rate, days to 250 lb, backfat, and loin eye area. Genetic change was measured as the change in average estimated breeding value (EBV) over years. Analysis was by a multitrait best linear unbiased prediction (BLUP) animal model with fixed effects of contemporary group and sex, and random effects of animal, litter, and residual error. The annual phenotypic trends from 1990 to 1999 were 0.008 lb, -0.85 d, -0.019 in., and 0.12 in. 2 for lean growth rate, days to 250 lb, backfat, and loin eye area. The overall genetic trends from 1990 to 1999 were 0.85, 0.28, 2.1, 0.95% of their means, respectively. The current rate of genetic improvement in the U.S. Landrace pigs is significant and offers the potential for considerable economic benefit.