High doses of phytase on growth performance, bone mineralization, diet utilization, and plasmatic myo-inositol of turkey poults

An experiment was conducted to evaluate the growth performance, bone mineral composition, diet utilization, and plasmatic concentration of myo-inositol (MYO) in turkeys fed different phytase doses from 1 to 28 d. A total of three hundred and twenty 1-day-old turkeys were distributed in a completely randomized design with 4 treatments and 8 replicates of 10 birds each. Treatments included a basal diet without phytase; reduced diet (reduced −0.15% available P and −0.18% Ca) without phytase; reduced diet + 2,000 units of phytase (FYT)/kg; and reduced diet + 4,000 FYT/kg. From day 26 to 28, partial excreta collection was conducted, and on day 28, 7 birds per replicate were euthanized for collection of ileal content and left tibia bones were removed from 2 of the same euthanized birds. Feed, excreta, and ileal digesta samples were analyzed to determine nutrient digestibility and metabolizability, ileal digestible energy, and AME. Tibia bones were analyzed for ash, Ca, and P content, and calculation of Seedor index. On day 28, blood samples were collected from 2 turkeys per replicate to analyze plasmatic MYO concentration. Feed conversion ratio was not affected, but phytase supplementation resulted in higher feed intake and body weight gain compared to turkeys fed the reduced diet (P < 0.05), and both doses were similar to the basal diet. Increasing the phytase dose had a linear effect (P < 0.05) on ileal digestibility of P and metabolizability of DM, CP, Ca, and Na, and also on AME. P content in the tibia bone increased linearly (P < 0.05) with phytase supplementation, and the same linear increase (P < 0.05) was observed for plasmatic MYO. In conclusion, the supplementation of turkey poult's diets with high levels of phytase up to 4,000 FYT/kg improves diet utilization by increasing P digestibility and dietary metabolizability, leading to higher P content in the bone and enhancing MYO provision and absorption.