Caecum

Abstract: The present work was undertaken to study the microbial activity in various segments of the gastrointestinal (GI) tract of pigs as influenced by the source and level of wheat and oat dietary fibre (DF). Eight experimental diets were prepared from wheat and oat fractions and studied in a series of two experiments using wheat flour as the DF-depleted control. The diets in Expt 1 were based on wheat flour and three iso-DF enriched diets comprising fractions rich in wheat aleurone, pericarp/testa or bran. In Expt 2, oat bran was added to wheat flour to achieve the same DF intake level as in Expt 1. This series included further diets based on rolled oats and rolled oats plus oat bran. The eight diets were given to thirty-two ileal-cannulated pigs, with sixteen pigs in each experiment. After a total period of 34 d (Expt 1) and 42 d (Expt 2), the pigs were slaughtered 4 h post-feeding and samples taken for adenine nucleotides (adenosine 5'-triphosphate (ATP); adenylate energy charge (AEC)), organic acids (lactic acid (LA); short chain fatty acids (SCFA)) and pH at twelve sites of the GI tract. The microbial activity as measured by the ATP concentration was low in the stomach and the cranial two-thirds of the small intestine, but tended to increase in the distal third. In the caecum a sharp rise in microbial activity was observed; the highest level was found for the diet providing most fermentable substrates. In all the diets but the rolled oats+oat bran diets, microbial activity showed a descending pattern as the digesta moved through the colon. In the large intestine source and level of residues had a marked influence on microbial activity. LA was the chief organic acid in the stomach and small intestine (10–40 mmol/l) while LA relative to SCFA was a minor component in the caecum and colon (10–20 mmol/l). The contribution of SCFA to total organic acids was reciprocal to LA, i. e. low in the stomach and small intestine (<20 mmol/l) and high in the caecum and colon. In the large intestine the concentration of SCFA decreased from 100–140 mmol/l in the caecum and proximal colon to 40–80 mmol/l in the distal colon. The acetic: propionic acid ratio increased from the caecum to the distal colon. With the diets based on oat alone (rolled oats; rolled oats+oat bran) the increase was less significant. DF addition and oats in particular increased the butyric acid molar ratio, from 0.06–0.08 for the wheat flour diet to 0.10–0.12 for the diet based on rolled oats+oat bran. For the same two diets the proportion of isobutyric and isovaleric acids increased more rapidly with the wheat-flour diet compared with the rolled oats+oat bran diet.

Abstract: Using histological and cultural techniques bacteria associated with the intestinal wall of the chick have been demonstrated. The main sites of adhesion were the crop, ileum and caecum. The pattern of attachment was characteristic for each site.

Abstract: 1. The concentrations of volatile fatty acids (VFA) in the rumen and caecum were compared when sheep were given barley or dried grass. The molar proportions of VFA in the caecum resembled those in the rumen except that the proportions of isobutyric and isovaleric acids were higher in caecal than in rumen fluid indicating an extensive breakdown of protein during fermentation in the caecum.2. The capacity for starch digestion in the large intestine was studied in two sheep receiving dried grass. Starch was infused into the caecum, the amount given increasing by daily increments of 20 g until 300 g daily were infused. Infused starch in excess of 138 g daily largely appeared in the faeces, indicating a limited but substantial capacity for starch fermentation in the large intestine. The infusion caused a marked increase in the molar proportion of butyric acid.3. Determinations made with a single sheep showed that the infusion of starch into the caecum caused large changes in the microflora, and species similar to Butyrivibrio became prevalent. The viable count on a starch medium was increased by 83 % by starch infusion.4. The infusions of starch increased the excretion of nitrogen in the faeces from 5.8 to 9.0 g daily. Using a fractionation procedure it was shown that when 100 g of starch were fermented in the large intestine the 'bacterial and endogenous debris' nitrogen increased by about 1.0 g. When starch was given orally to two sheep the increase in this fraction was about 0.4g nitrogen/100 g starch digested.5. It is suggested that dietary factors that cause changes in the site of fermentation from the rumen to the caecum will render less microbial nitrogen available to the host animal per unit of carbohydrate fermented and decrease the apparent digestibility of nitrogen.