Effect of dietary calcium concentration and exogenous phytase on inositol phosphate degradation, mineral digestibility, and gut microbiota in growing pigs. undefined

Variation in dietary Ca concentration may affect inositol phosphate (InsP) degradation and thereby P digestibility in pigs. The present study assessed effects of dietary Ca concentration and exogenous phytase on InsP degradation, nutrient digestion and retention, blood metabolites, and microbiota composition of ileal-cannulated growing pigs. In a completely randomized row column design with 4 periods, 8 ileal-cannulated barrows (initial bodyweight 27 kg) were fed 4 corn-soybean-and rapeseed meal-based diets containing 5.5 or 8.5 g Ca/kg dry matter (DM) without or with 1,500 FTU of an exogenous hybrid-6-phytase/kg diet. No mineral P was added, and the P concentration was 4.8 g P/kg DM. The prececal InsP6 disappearance in pigs fed diets with exogenous phytase was lower (P = 0.022) with additional Ca. Concentrations of InsP2-4 isomers and myo-inositol in distal ileum digesta and prececal P digestibility were greater (P 0.05). In conclusion, additional Ca reduced the exogenous phytase effect on prececal InsP6 degradation. Endogenous InsP degradation was impaired by additional Ca only in the hindgut, which may be related to the greater microbial diversity in feces compared to ileal digesta.