This study evaluated the effects of high phytase doses and soybean meal ( SBM ) with different CP content on growth performance, ileal nutrient digestibility, digestible energy, plasmatic myo -inositol, phosphate release in vitro, and bone composition of broiler chickens. One thousand two hundred 1-day-old broilers were distributed in a 2 × 2 completely randomized factorial arrangement, with 2 phytase doses (1,000 and 2,500 phytase units [ FYT ]/kg of feed) and 2 SBM with different CP concentrations (45 and 47%), totaling 4 treatments with 12 replicates of 25 birds each. The chickens received feed and water ad libitum. Diets were based on corn and SBM, with different inclusions of soybean hull used to dilute the CP content of SBM according to each treatment. The inclusion of 2,500 FYT increased weight gain from 0 to 21 d ( P < 0.05), whereas growth performance from 22 to 42 d was not affected, and SBM had no effect on growth performance. At day 21, ileal digestibility of dry matter, ash, and P, and digestible energy were greater in diets with 2,500 FYT/kg ( P < 0.05), as well as phosphate in vitro release ( P < 0.01) compared to the lower dose. At day 42, diets with SBM 47% CP and 2,500 FYT/kg promoted greater digestibility of dry matter, ash, CP, Ca, P, and digestible energy ( P < 0.001), and greater phosphate release ( P < 0.05) in comparison to other treatments. myo -inositol level in the plasma at 21 and 42 d was higher with the use of 2,500 FYT compared to 1,000 FYT ( P < 0.05). The higher phytase dose increased tibia ash, toe ash, and Seedor Index ( P < 0.05) at day 21, and the Ca content in tibia was higher with 2,500 FYT and SBM 47% CP at day 42. In conclusion, higher phytase doses for broilers improve weight gain, myo -inositol provision, and bone mineral composition. Nutrient ileal digestibility can be enhanced by higher phytase doses when in combination with SBM of greater nutritional quality.

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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.

Over the past years, turkey meat has gained a prominent position in the global market. As lysine (Lys) is among the main essential amino acids (AA) for protein deposition in the carcass, defining Lys requirements can contribute to improving the performance and carcass yield of turkey for meat production. Thus, the objective of this study was to evaluate if the digestible Lys levels proposed by breeder's guidelines are adequate to achieve the best performance in the used rearing and feed conditions of this study. In each phase, 800 female turkeys of the BUT (British United Turkey) hybrid strain were used. The turkeys were distributed in a completely randomized design in experiment 1 (initial phase: 0-25 d) and in a randomized block design in experiment 2 (growth phase: 26-48 d) and experiment 3 (finishing phase: 49-68 d). The treatments consisted of graded levels of digestible Lys with eight replications of 20 turkeys each. The digestible Lys levels tested were 13.6, 14.5, 15.8, 16.9 and 18.2 g/kg in the initial phase; 12.2, 13.2, 14.4, 15.4 and 16.2 g/kg in the growth phase; and 9.7, 10.4, 11.4, 12.1 and 13.7 g/kg in the finishing phase. The average daily gain (ADG), average daily feed intake (ADFI), feed efficiency (FE) and carcass yield (CY) were evaluated. The ADG, FE and CY data were improved by the digestible Lys levels (P < 0.05), and the data were adjusted to the quadratic and broken line functions. The digestible Lys level was estimated by the first intercept of the quadratic function with the plateau of the broken line function. At the end of experiment 3, the CY was evaluated (at 68 d). The digestible Lys level for better ADG and FE were, respectively, 16.69 g/kg and 16.55 g/kg in the initial phase, 14.25 g/kg and 14.15 g/kg in the growth phase, and 12.23 g/kg and 12.07 g/kg in the finishing phase. The digestible Lys level for CY was 12.32 g/kg. The current study concludes that digestible Lys levels are in the range of the nutritional guidelines for the strain used, except in the initial phase. Due to the difference in the initial recommendation, these levels should be validated in further investigations through performance trials.

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