Influence of phytase ormyo-inositol supplements on performance and phytate degradation products in the crop, ileum, and blood of broiler chickens
The objective of this study was to investigate the effects of supplementation with free myo-inositol (MI) or graded levels of phytase on inositol phosphate (InsP) degradation, concentrations of MI in the digestive tract and blood, bone mineralization, and prececal digestibility of amino acids (AA). Ross 308 broiler hatchlings were allocated to 40 pens with 11 birds each and assigned to one of 5 treatments. The birds were fed a starter diet until d 11 and a grower diet from d 11 to d 22. All diets were based on wheat, soybean meal, and corn. Birds were fed a control diet, calculated to contain adequate levels of all nutrients without (C) or with MI supplementation (C+MI), or one of 3 experimental diets that differed in phytase level (modified E. coli-derived 6-phytase; Phy500, Phy1500, or Phy3000 FTU/kg), with P and Ca levels adapted to the recommendations of the phytase supplier for a phytase level of 500 FTU/kg. The gain:feed ratio (G:F) was increased by MI or phytase in the starter+grower phase by 0.02 g/g. Prececal P and Ca digestibility, P and Ca concentration in blood serum, and tibia ash weight did not differ among treatments (P > 0.05). MI supplementation led to the highest MI concentration in the crop, ileum, and blood plasma across treatments. Phytase supplementation increased MI concentrations in the crop and ileum digesta in a dose-dependent manner and in plasma without any dose effect (P > 0.05). Prececal digestibility of some AA was increased by phytase. These outcomes indicate that MI might have been a relevant cause for the increase in G:F. Therefore, it is likely that the release of MI after complete dephosphorylation of phytate is one of the beneficial effects of phytase, along with the release of P and improvement in digestibility of other nutrients. Simultaneously, MI seems to have no diminishing effects on InsP degradation.