Fig. 1

Litter proportion distribution of gilts at different production level. The proportion distribution peaks of litter production in HP farms were shifted about two more than those in LP groups, respectively; and the proportion of low litter production (eight per litter or less) was lower than that in LP groups. Values represent Mean ± SEM. (HP farms, n = 11,833; LP-Total groups, n = 24,014; LP-BP groups, n = 10,952; LP-CP groups, n = 13,062). a,b,c,dBars with different letters differ significantly (P < 0.05)