Cereal dietary fibres influence retention time of digesta solid and liquid phases along the gastrointestinal tract

Abstract Nutrient digestion kinetics are determined by gastric emptying (GE) in the stomach and apparent mean retention time (aMRT) along the small and large intestine. This study aimed to evaluate the effects of cereal dietary fibres (DF), either as intrinsic components of plant foods or added ingredients, on the retention of solid and liquid phases of digesta along the gastrointestinal (GI) tract. Thirty pigs were fed one of five diets containing whole wheat (WW), wheat starch (WS) or wheat starch partially replaced by wheat arabinoxylan (AX) or oat β-glucan (βG), or in combination (WSAXβG). Indigestible solid and liquid phase markers were added to each diet and fed at i) constant and ii) pulse dose intervals. Constant markers (acid insoluble ash and chromium) provided aMRT along 11 sections of the GI tract, while pulse dose markers (cerium, ytterbium and cobalt), fed 2–6 h before anaesthesia, provided a GE time. aMRT was slowest in the caecum and large intestine (LI, 15.4h), followed by the small intestine (SI, 3.4h) and stomach (2.6h) with liquid phases moving faster compared to solid phases. Between DF, AX but not βG, delayed GE of solid and liquid contents and showed longer retention time in SI and LI. In the absence of isolated soluble fibres, WS and WW diets showed similar flow characteristics of solid and liquid phases. The aMRT was shown to be dependent on the structure and swellability of added DF.