An in vitro experiment was conducted to assess the microbial activity of faeces from unweaned and weaned piglets. Diets of weaned piglets were supplemented with various fructans. Weaned piglets received a corn¿soy based basal diet supplemented with either corn starch (control; CON), oligofructose (OF), chicory root (CHR), a mixture of chicory pulp and oligofructose (MIX; 60:40) or corn starch and antibiotic (CONAB). Faecal inocula collected from unweaned (5 kg body weight (BW)) and weaned piglets (15 kg BW) were introduced in airtight 100-mL bottles containing 0.5 g of substrate (basal or mix) in pre-warmed buffered medium. The organic matter cumulative volume (OMCV) was measured for 48 h, and a mono-phasic model was fitted to the data. The concentration of volatile fatty acids (VFA) and ammonia (NH3) was determined after fermentation. Incubation of substrate mix with the different inocula gave a significant higher OMCV compared to substrate basal, except for the inoculum from piglets of the CONAB group. In addition, substrate mix gave a higher Rmax and a lower Tmax compared to substrate basal. With the exception of inoculum obtained from chicory root supplemented animals (CHR) no substrate effects were observed in fermentation end-products (VFA and NH3). However, the proportions of acetic acid were significantly higher and those of butyric acid lower when inocula were incubated with substrate mix. Inocula from weaned pigs tended to show higher proportions of propionic acid when incubated with substrate mix, whilst inocula from unweaned piglets showed the opposite. The differences in fermentation kinetics between substrates after incubation with inocula from weaned and unweaned piglets in combination with an altered composition in VFA, points to a modified faecal microflora following weaning.