This study aimed to evaluate the genetic relationship between faecal microbial composition and five feed efficiency (FE) and production traits, residual feed intake (RFI), feed conversion ratio (FCR), daily feed intake (DFI), average daily gain (ADG) and backfat thickness (BFT). A total of 588 samples from two experimental pig lines developed by divergent selection for RFI were sequenced for the 16 rRNA hypervariable V3-V4 region. The 75 genera with less than 20% zero values (97% of the counts) and two alpha-diversity indexes were analysed. Line comparison of the microbiota traits and estimations of heritability (h(2)) and genetic correlations (r(g)) were analysed. A non-metric multidimensional scaling showed line differences between genera. The alpha-diversity indexes were higher in the LRFI line than in the HRFI line (p < .01), with h(2) estimates of 0.19 +/- 0.08 (Shannon) and 0.12 +/- 0.06 (Simpson). Forty-eight genera had a significant h(2) (>0.125). The r(g) of the alpha-diversities indexes with production traits were negative. Some r(g) of genera belonging to the Lachnospiraceae, Ruminococcaceae, Prevotellaceae, Lactobacillaceae, Streptococcaceae, Rikenellaceae and Desulfovibrionaceae families significantly differed from zero (p < .05) with FE traits, RFI (3), DFI (7) and BFT (11). These results suggest that a sizable part of the variability of the gut microbial community is under genetic control and has genetic relationships with FE, including diversity indicators. It offers promising perspectives for selection for feed efficiency using gut microbiome composition in pigs.