Effects of pea extrusion and enzyme and probiotic supplementation on performance, microbiota activity and biofilm formation in the broiler gastrointestinal tract.

1. The effects of supplementation of broiler chicken diets with pea meal, carbohydrase enzymes and a probiotic were investigated for potential performance improvement. 2. Raw or extruded pea meal (cv Model, grown in Poland) was included in a wheat-soybean meal-based diet at 250 g/kg. The diets were unsupplemented (control) or supplemented with either carbohydrase enzymes (200 U/kg xylanase and 10 U/kg β-glucanase in feed) or a probiotic (Bacillus subtilis), or both. The diets were fed to Ross 308 broilers aged 9-28 days. 3. After two additional days, chick gastrointestinal tracts were excised and analysed for the presence of Bacillus subtilis biofilm; and the ileal and caecal digesta were analysed for bacterial enzyme activities and to determine the concentration of short-chain fatty acids (SCFAs). 4. Feeding the pea-based diet supplemented with the probiotic compromised feed utilisation, due to higher feed intake. The addition of enzymes to the raw, but not the extruded, pea containing diet partially ameliorated this effect (pea form × additives; P < 0.002). 5. In the ileal digesta, interactions between the dietary treatments were observed for the activities of all bacterial glycolytic enzymes and for SCFA concentrations. β-glucosidase, α-galactosidase and β-glucuronidase were highest in birds fed the diet containing extruded pea supplemented with the probiotic and enzymes (pea form x additives; P = 0.018 to P < 0.006). In the caecal digesta, interactions were observed for bacterial enzyme activities, but not for total SCFA concentration. Biofilm formation in the caecum indicated that the probiotic strain was metabolically active in the broiler gut. 6. In conclusion, supplementation of diets containing raw or extruded pea meal with enzymes and a Bacillus subtilis spore-based probiotic modulated microbiota activity but had no clear effects on broiler performance. Probiotic administration did not cause excessive fermentation in the ileum and caecum but enhanced Bacillus subtilis spp. biofilm formation in the caecum, which may be indicative of a beneficial effect on gut health.