In vitro fermentation if fructo-oligosaccharides and trans galacto-oligosaccharides by adapted and unadapted bacterial populations for the gastrointestinal tract of piglets

Abstract

An in vitro study was performed to investigate the fermentation of fructo-oligosaccharides (FOS) and transgalacto-oligosaccharides (TOS) by bacteria harvested from the gastrointestinal tract of piglets. In addition, the apparent ileal digestibility of FOS and TOS was measured. Thirty piglets were fed either a semi-synthetic control diet or the control diet supplemented with 40 g FOS or 40 g TOS per kg (n = 10). After 29 days, the piglets were killed and the gastrointestinal contents collected for the in vitro experiment and chemical analysis. The results demonstrated that bacteria from the stomach were nearly incapable of degrading FOS and TOS, whereas bacteria from the distal small intestine to some extend fermented FOS and TOS. Fermentation of FOS and TOS with bacteria from the stomach and distal small intestine was not affected by the dietary treatment of the piglets. Bacteria from the caecum and mid colon of the piglets showed the highest capacity to degrade FOS and TOS in vitro and the microbiota seemed to adapt to the dietary FOS. Caecal bacteria from piglets fed the FOS diet had tendencies to increased production rate of organic acids (P < 0.1), propionic acid (P < 0.1) and valeric acid (P < 0.1) and significantly higher production rate of butyric acid (P < 0.05) from FOS as compared with bacteria from piglets fed the control and TOS diet. Colonic bacteria from piglets fed the FOS diet also had significantly higher production rates of butyric acid (P < 0.05) and capronic acid (P < 0.01). In addition, significantly lower molar proportions of acetic acid (P < 0.05) and propionic acid (P < 0.05), and a significantly higher molar proportion of capronic acid (P < 0.05) were observed for colonic bacteria from piglets fed the FOS diet as compared with the control diet. Fermentation of TOS by bacteria from the caecum and mid colon was generally not affected by the dietary treatment of the piglets. It was estimated that the capacity for microbial degradation of the dietary FOS and TOS during passage of the stomach and small intestine of the piglets was approximately a proportion of 0.20 for FOS and 0.16 for TOS. The coefficient of apparent ileal digestibility (CAID) was 0.57 (range 0.39–0.89) for FOS and 0.56 (range 0.31–0.82) for TOS. In conclusion, a proportion between 0.20 and 0.60 of FOS and TOS are degraded by the microbiota in the small intestine of piglets and the microbiota of the large intestine adapt to the administration of FOS in the feed.