Selection for daily gain, loin-eye area, backfat thickness and intramuscular fat based on desired gains over seven generations of Duroc pigs

To develop an excellent line of Duroc breed in performance traits and meat quality traits, selection of that breed was conducted over seven generations for growth rate (DG), real-time ultrasound loin eye muscle area (EM), backfat thickness (BF), and intramuscular fat content (IMF) based on desired gains. Those performance traits were measured in 1646 pigs. Meat quality traits were measured in 547 pigs. Meat quality traits were IMF and tenderness (TEND) in M. longissimus that was taken two sections above the last rib and measured 24 h after slaughter. Selection was based on a selection index method that included four traits at the first and second generations of selection: DG, EM, BF, and IMF. After the third generation, EBVs for four traits were obtained from analyses of performance and meat quality data. Respective heritability estimates for DG, EM, BF, IMF, and TEND were 0.48, 0.45, 0.72, 0.46, and 0.45. The IMF was correlated positively with DG (genetic correlation r_G: 0.23, phenotypic correlation r_P: 0.07) and BF (r_G: 0.24, r _P: 0.21); it was correlated negatively with EM (r_G: - 0.24, r_P: - 0.24). Selection and correlated responses were estimated from predicted breeding values using genetic parameters derived from multivariate REML analysis. Those responses corresponded well with DG and IMF.