The efficacy of 2 phytases on inositol phosphate degradation in different segments of the gastrointestinal tract, calcium and phosphorus digestibility, and bone quality of broilers

The anti-nutritional effects of dietary inositol phosphates (IP(6) through IP(3)) have been recognized in broiler chickens; however, inositol hexaphosphate (IP(6)) is more potent than the lower IP esters. The efficacies of 2 commercial phytases, a Buttiauxella sp. phytase (BSP) and a Citrobacter braakii phytase (CBP) at 500 and 1,000 FTU/kg, were studied on IP(6–3) concentrations in the crop, proventriculus + gizzard, and distal ileum digesta, and ileal IP(6) disappearance in broilers at day 22. Apparent ileal P and Ca digestibility, and bone quality at days 22 and 33 were also measured. Female Ross 308 broilers (n = 1,890; 30 birds × 7 diets × 9 replicates) were fed corn-soy-based crumbled diets. The 7 diets included a primary breeder recommendation-based positive control diet (PC); the PC marginally reduced in available P by 0.146% and Ca by 0.134% of the diet, (NC1) or moderately reduced by 0.174 and 0.159% of the diet, respectively (NC2). Other diets were the NC1 + BSP or CBP at 500 FTU/kg (NC1+500BSP and NC1+500CBP) and the NC2 + BSP or CBP at 1,000 FTU/kg (NC2+1,000BSP and NC2+1,000CBP). Each of the NC1 and NC2 had distal ileum IP(6) disappearance similar to that of PC, but each had lower P digestibility and the majority of measured bone quality parameters than the PC. The ileal IP(6) levels were decreased by 52.0 and 32.7% for NC1+500BSP and NC1+500CBP, respectively, relative to NC1 and by 73.6 and 50.9% for NC2+1,000BSP and NC2+1,000CBP, respectively, relative to NC2 (P < 0.001), with a similar effect for distal ileum IP(6) disappearance. Overall, phytase in the NC diets increased P digestibility, and femur breaking strength and cortical bone mineral density at days 22 and 33. Overall, each of the phytases at each dose degraded IP(6–3) across the gastrointestinal tract segments to increase P digestibility and the P and Ca utilization in bone. However, dietary BSP at 1,000 FTU/kg was most effective. Supplemental phytase degrades phytate to decrease the anti-nutritional effects in a dose- and phytase-dependent manner.