Functional interactions of manno-oligosaccharides with dietary threonine in chicken gastrointestinal tract: III. Feed passage rate

1. A 3 x 2 factorial experimental design was used to investigate the interaction between threonine concentration (0·70, 1·0 and 1·3 of National Research Council (NRC), 1994, recommendations) and manno-oligosaccharides (0 and 2 g/kg) on feed passage rate in relation to intestinal microbial activities and crude mucin turnover. 2. There was no interaction between the effects of manno-oligosaccharides (MOS) and dietary threonine on total tract transit time. However, an interaction between MOS and threonine was apparent where increasing threonine in the absence of MOS led to a reduction in the mean retention time, but a trend in the opposite direction in the presence of MOS. The ileal mean retention time at deficient and adequate concentrations of threonine was also significantly shorter in the presence of MOS. 3. In the jejunum, dietary MOS interacted with threonine to increase the villus-to-crypt ratio with deficient and adequate concentrations of threonine but not with an excess. In the ileum, MOS had no effect on the villus-to-crypt ratio at the deficient and adequate concentrations of threonine but significantly increased the ileal villus-to-crypt ratio with an excess. 4. There were significant interactions between MOS and dietary threonine in their effects on ileal flow of crude mucin, with MOS supplementation increasing mucin concentration and output when threonine was adequate but not when deficient or in excess. 5. Neither MOS nor threonine affected volatile fatty acids and intestinal musculature. No effects of gut microflora or voluntary feed intake on feed passage rate was attributable to dietary threonine or MOS supplementation.