Effects of dietary oligosaccharides on microbial diversity and fructo-oligosaccharide degrading bacteria in faeces of piglets post-weaning

Newly weaned 4-week-old piglets were fed a semi-synthetic diet supplemented with 40 g fructo-oligosaccharides (FOS) or 40 g transgalacto-oligosaccharides (TOS) per kg replacing 20 g maize starch and 20 g cellulose per kg in the control diet. Faecal samples were collected on days 0, 3, 7, 14 and 28 after weaning and analysed for dry matter, pH, organic acid concentration and distribution, microbial populations and identity of dominant bacterial species able to ferment FOS. The oligosaccharide addition to diets had no effect on growth performance of the piglets. Dietary oligosaccharides and time after weaning did not affect faecal dry matter content. There was no effect of diet on faecal pH and total organic acid concentration, but the pH decreased (P < 0.001) and total organic acid concentration increased (P < 0.001) during the period after weaning. Faecal bacterial populations (total culturable, anaerobic bacteria, lactic acid bacteria, lactobacilli, bifidobacteria, coliforms and lactose-negative enterobacteria) were not affected by diet. The faecal population of yeast was significantly higher in piglets fed the TOS-diet as compared to piglets fed the FOS-diet (P < 0.05) and control diet (P < 0.001). The population of yeast was also higher in piglets fed the FOS-diet as compared to those fed the control diet (P < 0.05). In the faeces of piglets fed the control diet, the level of FOS-degrading bacteria was significantly lower than the level of saccharolytic bacteria (P < 0.01). This difference was not observed in the faeces of piglets fed the FOS-diet, indicating that the microbial population changed in response to the dietary FOS. A 16S rDNA-based identification of the FOS-degrading bacteria indicated that several different species of bacteria present in faeces of piglets are able to ferment FOS. It was concluded that oligosaccharide supplementation in diets to piglets after weaning had no effect on growth performance, and no or little effect on physico-chemical characteristics and bacterial populations of faeces. A strong stimulating effect on the faecal population of yeast was observed and the impact of this on pig performance is discussed. (C) 2003 Elsevier B.V. All rights reserved.