In an experiment with 33 first-litter sows from day 90 of pregnancy to day 28 of lactation, the influence of a probiotic supplementation on weight performance, feed intake, litter sizes, litter weights, health status and microbiological profile was tested. Enterococcus faecium DSM 7134 was supplemented in a concentration of 5 x 10(8) CFU/kg feed to the gestation and lactation diets of gilts. The supplemented sows showed a significant higher improvement of feed intake (4.16 vs. 3.71 kg/day), litter size (9.2 vs. 7.7 piglets) and weight performance. The average live weight of the probiotic sows at day 28 of lactation was 11 kg higher than of the controls. The bacterial counts/g faeces (lactobacilli, Gram-positive anaerobes, Gram-negative anaerobes, Escherichia coli and enterococci) and the incidence of adhesive and haemolytic E. coli organisms revealed no significant differences between the sows of the two groups or their piglets. While the litter size cannot necessarily be assumed as a primary effect of the probiotic supplementation, the significantly better feed intake and weight performance might be partly due to the probiotic use and can prevent "starvation sterility" of young sows after their first litter caused by reduced feed intake during lactation with high mobilization of body tissue accompanied with lack of energy.