Different phytase levels and energy densities in broiler diets on performance, nutrient digestibility, and bone integrity from 28 to 35 days of age

ABSTRACT The study was carried out with the objective of evaluating the effects of using phytase levels at different energy densities in the diet of broilers, from 28 to 35 days of age. The experimental diets contained increasing levels of apparent metabolizable energy corrected for nitrogen balance and different levels of phytase. Growth performance variables, nutrient digestibility, as well as variables related to bone integrity were examined. Diets containing 500 FTU/kg in combination with 3150kcal.kg-1 of AMEn resulted in better growth performance. Supplementation with 500 and 1000 FTU/kg in the diets provide better coefficients of apparent and ileal digestibility of calcium and phosphorus, but negatively influence the deposition of calcium, phosphorus, dry matter, and ash in the tibia, in addition to adversely affecting the breakage and area of these bones in broilers. Bone length and the levels of magnesium and zinc present in the tibias were not influenced by the energy and phytase levels of the diets. There is no interaction between the different energetic densities and the phytase doses in the variables analyzed in the studied period. Increasing the energy density of diets resulted in improved apparent and ileal digestibility for most nutrients.

摘要
本研究旨在评估28至35日龄肉仔鸡日粮中，不同植酸酶水平与不同能量密度配伍的应用效果。试验日粮设置了梯度递增的氮平衡校正表观代谢能（AMEn）水平，并搭配不同剂量的植酸酶。本研究测定了生长性能指标、养分消化率及骨骼完整性相关参数。
当日粮添加500植酸酶单位（FTU）/千克且AMEn水平为3150 kcal·kg⁻¹时，肉仔鸡的生长性能表现最优。日粮中添加500与1000 FTU/kg植酸酶可提升钙与磷的表观消化率与回肠消化率，但会对胫骨中钙、磷、干物质及灰分的沉积产生负面影响，同时对肉仔鸡胫骨的断裂强度与横截面积造成不利影响。日粮能量密度与植酸酶水平对胫骨长度、胫骨中镁与锌的含量无显著影响。在本试验周期内分析的所有变量中，不同能量密度与植酸酶添加剂量之间不存在交互效应。提升日粮能量密度可改善绝大多数养分的表观消化率与回肠消化率。