Effect of type and level of fibre on gastric microbial activity and short-chain fatty acid concentrations in gestating sows

Abstract

The present study was undertaken to study the effect of dietary fibre on gastric microflora, and short-chain fatty acids (SCFA) concentrations at different time after feeding in gestating sows. Three experimental diets consisting of two dietary fibre-rich diets and one concentrated, low dietary fibre diet (C) were used. One fibre-rich diet contained soluble dietary fibre from sugar beet pulp (S) and the other contained insoluble dietary fibre from wheat bran (W). The experiment was carried out as repeated 3×3 Latin squares with six gastric-cannulated gestating sows fed one of the three experimental diets, with experimental periods of 7 days, comprising 3 days of adaptation to each diet, followed by 4 days of collection of gastric digesta. The gastric digesta were evacuated once daily through the gastric cannula in a randomized order 0.5, 1, 2, 3, 5 and 15.5 h after feeding the morning meal. The evacuated gastric digesta were quantified and a representative sample collected for measuring pH, dry matter (DM) content, SCFA, density of various bacterial populations (including coliform bacteria, lactic acid bacteria, lactobacilli, enterococci and yeasts), adenosine 5′-triphosphate (ATP), and adenylate energy charge (AEC). With all three diets, gastric pH was highest at 0.5 h after feeding, and then fell gradually with increasing time (especially between 0.5 and 2 h) after feeding. The changing trend of pH with the three diets was not significantly different. The total counts of coliform bacteria, lactic acid bacteria, lactobacilli, enterococci and yeasts were also highest at 0.5 h after feeding, in agreement with gastric pH values. The population of coliform bacteria with diet S decreased significantly compared with diet C or diet W ( P<0.05). The concentration of gastric ATP was highest at 15.5 h after feeding. The level of acetate had the lowest value at 0.5–1 h with diets S and C, but at 2 h with diet W. In conclusion, gastric pH was unstable at different time after feeding, and was highest at 0.5 h after feeding. The highest populations of various gastric bacteria were found at 0.5 h after feeding, irrespective of type of diet. As gastric pH increased, gastric microbial activity was inhibited. The populations of lactic acid bacteria and lactobacilli with the insoluble dietary fibre were always higher than with the soluble dietary fibre at all times after feeding. Soluble dietary fibre increased the level of acetate.