The Tai Zumu composite line was created in 2001 by the French pig organization GENE+ to produce and select 50% Meishan grand-maternal dams. We studied the genetic components of piglet and sow production in that population bred in 3 nucleus herds. From 2008 to 2012, 25,763 piglets were weighed at birth (T0) and 17,604 piglets were weighed at 3 weeks of age (T3). Sow production traits (age AG, backfat thickness BF) were recorded at 100kg from 19,763 sows. Variance components were estimated using the restricted maximum likelihood methodology applied to animal models. Numbers of piglets born alive (NBA) and weaned by a sow (NW) were recorded. Growth traits included the mean piglet weight (MW), the direct (d) and maternal (m) genetic effects on piglet weight and the standard deviation of weights within the litter (SD). The heritability for MW was higher at T0 than at T3 (0.51 and 0.26). Heritability estimates were lower for NBA and NW (0.20/0.06) and piglet weight SDT0 and SDT3 (0.19/0.15), and were highest for sow production traits (0.67 for BF, 0.38 for AG). Heritability for d and m on piglet weight were similar at T0 (hd²=0.05; hm²=0.16) and T3 (hd²=0.08; hm²=0.14) and a genetic antagonism between the two effects was obtained at T3 (-0.38±0.17). Strong unfavorable genetic correlations were found between NBA and MWT3 (-0.73±0.13); whereas genetic correlations of SDT3 with NBA and MWT3 were lower (0.10±0.20; 0.28±0.20). Genetic correlations of AG and BF were favorable with MWT3 with MWT3 (-0.39±0.09;-0.32±0.09) but unfavorable with SDT3 (-0.35±0.12;-0.39±0.11). The results suggest that selection for NBA might increase NW (rg=0.39±0.19) and that the breeding objective should also include homogeneity of piglet weights and piglet growth during lactation with use of both direct and maternal effects. This strategy will be assessed by analysis of response to selection with comparison of alternative breeding programs.