Maternal and direct genetic parameters for production traits and maternal correlations among production and feed efficiency traits in Duroc pigs

Direct and maternal genetic parameters for production traits in 1,642 pigs and maternal genetic correlations among production (1,642 pigs) and feed efficiency (380 boars) traits were estimated in 7 generations of a Duroc population. Traits studied were daily gain (DG), intramuscular fat (IMF), loineye area (LEA), backfat thickness (BF), daily feed intake (FI), feed conversion ratio (FCR) and residual feed intake (RFI). The RFI was calculated as the difference between actual and predicted feed intake. The predicted feed intake was estimated by adjusting the initial test weight, DG and BF. Data for production traits were analyzed using four alternative animal models (including direct, direct+maternal permanent environmental, or direct+maternal genetic+maternal permanent environmental effects). Direct heritability estimates from the model including direct and all maternal effects were 0.41 +/- 0.04 for DG, 0.27 +/- 0.04 for IMF, 0.52 +/- 0.06 for LEA and 0.64 +/- 0.04 for BF. Estimated maternal heritabilities ranged from 0.04 +/- 0.04 to 0.15 +/- 0.05 for production traits. Antagonistic relationships were observed between direct and maternal genetic effects (r(am)) for LEA (421). Maternal genetic correlations of feed efficiency traits with FI (r(g) of FI with FCR and RFI were 0.73 +/- 0.06 and 0.90 +/- 0.05, respectively) and LEA (r(g) of LEA with FCR and RFI were -0.48 +/- 0.05 to -0.61 +/- 0.05, respectively) were favorable. The estimated moderate genetic correlations between direct and maternal genetic effects for IMF and LEA indicated that maternal effects has an important role in these traits, and should be accounted for in the genetic evaluation system.