Genetic parameter estimates for average daily gain and backfat thickness in Pietrain swine breed

Accurate estimates of genetic parameters for desirable economic traits in swine production, such as average daily gain (ADG) and backfat thickness (BFT) are essential for optimizing genetic response to selection. The aim of this study was to estimate genetic parameters using different models for ADG and BFT adjusted to 100 kg in Pietrain pigs. Data on 2,782 and 2,739 animals produced by 137 sires, 342 dams and 112 founders were considered in analyzing ADG and BFT, respectively. Average inbreeding coefficient was 0.01 and mean and standard error for ADG and BFT were 591.38 ? 62.52 g/d and 8.86 ? 1.57 mm, respectively. The significant fixed effects (P<0.01) sex of the animal (male or female), month (from January to December) and year (from 1997 to 2015) of birth of the animal were used to form the contemporary groups (CG). Genetic parameters and standard errors were estimated by the average information restricted maximum likelihood (AIREML) method in single and two-trait analyses performed on Wombat software. Four models were studied in single-trait analyses to define the most fitting to our data. All four models included the fixed effects of CG and different random effects: Model 1 considered additive genetic direct and residual effects; Model 2 included additive genetic direct, maternal genetic and residual effects; Model 3 included additive genetic direct, common litter and residual effects and Model 4 included additive genetic direct, maternal genetic, common litter and residual effects. The likelihood ratio test (LRT<) was verified between all models and Model 3 was the most fitted. The direct heritability estimates were 0.25 ? 0.05 and 0.18 ? 0.05 for ADG and BFT, respectively. The common litter environmental effects were 0.12 ? 0.02 and 0.07 ? 0.02 for ADG and BFT, respectively. The positive genetic correlations between ADG and BFT (0.442 ? 0.16) indicated that selection programs to improve these traits must be based on indirect selection. Results suggest the possibility of obtaining genetic gains for these traits by genetic selection. The common litter effect must be considered for ADG and BFT.