The effect of cereal-derived beta-glucans and exogenous enzyme supplementation on intestinal microflora, nutrient digestibility, mineral metabolism and volatile fatty acid concentrations in finisher pigs

Two experiments were conducted to investigate the effects of cereal type, β-glucan type and exogenous enzyme supplementation (ES) on microbial populations, volatile fatty acid (VFA) concentrations, nutrient digestibility, indole and skatole levels in the digesta and mineral metabolism in pigs. In Experiment 1, 28 boars (59 ± 2 kg; 119 ± 2 days of age) were used in a 2 × 2 factorial arrangement and were assigned to one of 4 dietary treatments (n = 7): T1) barley-based diet; T2) barley-based diet plus ES; T3) oat-based diet and T4) oat-based diet plus ES. The ES used in both experiments contained endo-1,3-β-glucanase and endo-1,4-β-xylanase. In Experiment 2, 28 boars (60 ± 1.9 kg; 119 ± 2 days of age) were assigned to one of 4 dietary treatments (n = 7): T1) oat-based diet containing endogenous (non-purified) β-glucans; T2) oat-based diet containing endogenous β-glucans plus ES; T3) wheat-based diet and exogenous (laboratory purified) β-glucans and T4) wheat-based diet and exogenous β-glucans plus ES. The laboratory purified exogenous β-glucans used in Experiment 2 were oat-derived β-glucans. The diets were equalised to have similar amount of total β-glucan and arabinoxylan. In Experiment 1, pigs offered barley-based diets had higher (P<0.001) coefficient of total tract apparent digestibility (CTTAD) of organic matter (OM) and gross energy (GE) and lower CTTAD (P<0.05) of nitrogen compared to oat-based diets. Pigs offered barley-based diets had higher (P<0.001) molar proportions of butyric and propionic acids and higher total VFA concentrations in the caecum (P<0.01) and colon (P<0.001) than pigs fed oat-based diets. Pigs offered oat-based diets had higher populations of Bifidobacteria in the ileum (P<0.05) and colon (P<0.01), and Lactobacilli in the colon (P<0.05) compared with pigs fed barley-based diets. In Experiment 2, pigs offered diets containing endogenous β-glucans without ES had higher populations of Bifidobacteria (P<0.01) compared to pigs offered diets supplemented with exogenous β-glucans without ES. Diets containing endogenous β-glucans without ES had a lower (P<0.001) CTTAD of OM and GE compared to diets supplemented with exogenous β-glucans without ES. In conclusion, barley-based diets have more beneficial effects on parameters related to gut health than oat-based diets; however oat-based diets exhibit higher potential to enhance beneficial microbial populations. Endogenous β-glucans show better prebiotic properties than exogenous β-glucans.