Dietary supplementation with chitosan at high and low crude protein concentrations promotes Enterobacteriaceae in the caecum and colon and increases manure odour emissions from finisher boars

The hypothesis of this study is that supplementation of a high crude protein (CP), wheat-based diet with chitosan may increase protein-fermenting bacteria in the large intestine at the expense of carbohydrate-fermenting bacteria, resulting in increased manure odour emissions. A 2 × 2 factorial experiment was conducted to investigate the effect of dietary chitosan inclusion (0 vs 20 g/kg) and CP concentration (200 vs 150 g/kg) on intestinal microflora, volatile fatty acid concentrations (VFA) and manure odour from finisher boars. The inclusion of chitosan decreased Lactobacilli and increased Enterobacteriaceae in the caecum (P < 0.05) and colon (P < 0.001) compared with pigs offered unsupplemented diets. Dietary chitosan decreased the molar proportion of butyric acid and increased valeric acid in the caecum (P < 0.05) and colon (P < 0.001) compared with unsupplemented diets. Dietary chitosan increased manure odour emissions (P < 0.05) at 72 h post excretion. In conclusion, dietary chitosan decreased Lactobacilli and increased Enterobacteriaceae in the hind gut and subsequently increased manure odour emissions.