A Bacillus probiotic administered to sows was evaluated to determine the effect on their litters and subsequent pig growth response during the nursery phase. The study included 500 sows (250 sows/trt) fed a control or treatment diet with two Bacillus subtilis strains administered at 3.7x105 CFU/g of feed beginning three days after mating. Pigs (n=1,100) weaned from the sow phase were divided into 44 pens (22 pens/trt) and fed a common diet to determine the effect of sow treatment on post-weaning growth performance. Fecal samples were collected from a subset of sows (25/trt) at d112 of gestation and d19 of lactation, and from two pigs/pen in the nursery on d3 post-weaning for microbial enumeration. A blood sample was obtained from two pigs/pen on d3 and serum cytokines and the acute phase protein, α-1-acid glycoprotein (AGP) were quantified. Data were analyzed using the MIXED procedure of SAS; sow/litter and pen served as the experimental unit. Litter weaning weights did not differ, but Escherichia coli counts were lower (P≤0.05) on d112 in fecal samples from sows fed Bacillus compared to control sows. Lactic acid bacteria counts were greater (P≤0.01) on d3 post-weaning in pigs weaned from sows fed Bacillus compared to control pigs. Nursery pigs weaned from sows fed the Bacillus probiotic had greater (P≤0.01) ADG and G/F during Phase1 (d 0-11), greater (P≤0.01) ADG and ADFI during Phase3 (d 23-37) and were 0.91 kg heavier (P≤0.01) at the end of the nursery phase (d 51) compared to pigs from control sows. The administration of Bacillus to sows resulted in lower AGP (P≤0.05) and greater tumor necrosis factor-α (P=0.08) serum concentrations on d3 post-weaning and reduced (P≤0.05) the percentage of nursery pigs removed from the trial and placed in invalid pens compared to pigs from control sows. These data indicate that a Bacillus probiotic improves sow health and the lactation environment and has a substantial impact on the subsequent productivity of their progeny.