Does selection for RFI affect the sensitivity to environmental variation in pigs ?

Data were recorded in two lines divergently selected for residual feed intake (RFI) for eight generations (G0 to G7). First, an animal mixed model was applied to the full dataset to estimate least square means (LsCG) of contemporary group (CG) effects for average daily gain (ADG, 3189 pigs, 80 CG) and backfat thickness (BFT, 1668 pigs, 44 CG). Second, LsCG were used as covariates in linear models on these traits to estimate line specific regression coefficients in the later generations of selection (G6 and G7). The low RFI line showed lower regression coefficients for ADG than the high RFI line (0.05≤P<0.11), indicating lower sensitivity to environmental variations. No difference was evidenced for BFT. Contrary to the literature, increased sensitivity to environmental variability was observed for higher RFI pigs, not for lower RFI, challenging the understanding of RFI as a buffer to face stresses.