微生物植酸酶可改善11 ~ 130 kg猪只因低钙日粮导致的骨吸收
本试验旨在验证在11 ~ 130 kg猪只阶段，短期试验中以标准化全肠道可消化（STTD）Ca和STTD P比值来表示钙的需求量在添加或不添加微生物植酸酶的饲粮中是适用的。
试验分5个阶段，选用160头猪（体重：11.2±1.8kg）被随机分配给32栏和4个日粮组中，采用2 × 2因子设计，2种日粮配方本质（总Ca和STTD Ca）和2种植酸酶水平（0或500单位/kg饲料），假设植酸酶释放0.11% STTD P 和0.16% 总Ca。5个阶段中STTD Ca：STTD P分别为1.40：1、1.35：1、1.25：1、1.18：1、1.10：1， STTD P满足需要量；每阶段结束时，记录猪只的体重和剩余饲料量。在第1阶段（24天）结束时，每栏1头猪被实施安乐死，采集血液和右股骨样本。在第2～5阶段结束时，从每个猪圈的同一头猪身上采集血液样本。试验结束时（126天），每栏采集1头猪右股骨，测定其胴体性状。
试验数据显示，在任何阶段，饲粮配方本质和植酸酶添加量对生长性能均未发现相互作用，各处理对整体生长性能也未发现差异。第一阶段结束时血浆钙、磷和骨灰分也不受饲粮处理的影响。试验第126天，以总钙为基础的非植酸酶饲粮的骨灰分高于以STTD Ca为基础的饲粮；但在植酸酶饲粮中，两种钙基础饲粮的骨灰分没有差异（交互作用，P < 0.05）。在第2和3阶段末，不添加植酸酶的饲粮血浆P显著高于添加植酸酶的饲粮（P < 0.05），但在第4和5阶段末无显著差异。在2 ~ 5阶段血浆钙浓度呈负的二次效应（P < 0.05），血浆磷浓度在2～5阶段显著增加（二次方程式关系，P < 0.05）。然而，饲粮配方本质和植酸酶含量对胴体特征无交互作用或影响。
由此可见，STTD Ca：STTD P值可用于生长肥育猪饲粮配方，且不影响生长性能和胴体性状，植酸酶添加可改善低钙、低磷日粮导致的骨吸收。
Formulating diets based on digestible calcium instead of total calcium does not affect growth performance or carcass characteristics, but microbial phytase ameliorates bone resorption caused by low calcium in diets fed to pigs from 11 to 130 kg
An experiment was conducted to test the hypothesis that the requirement for Ca expressed as a ratio between standardized total tract digestible (STTD) Ca and STTD P obtained in short-term experiments may be applied to pigs fed diets without or with microbial phytase from 11 to 130 kg. In a 5-phase program, 160 pigs (body weight: 11.2 ± 1.8 kg) were randomly allotted to 32 pens and 4 corn–soybean meal-based diets in a 2 × 2 factorial design with 2 diet formulation principles (total Ca or STTD Ca), and 2 phytase inclusion levels (0 or 500 units/kg of feed) assuming phytase released 0.11% STTD P and 0.16% total Ca. The STTD Ca:STTD P ratios were 1.40:1, 1.35:1, 1.25:1, 1.18:1, and 1.10:1 for phases 1 to 5, and STTD P was at the requirement. Weights of pigs and feed left in feeders were recorded at the end of each phase. At the conclusion of phase 1 (day 24), 1 pig per pen was euthanized and a blood sample and the right femur were collected. At the end of phases 2 to 5, a blood sample was collected from the same pig in each pen. At the conclusion of the experiment (day 126), the right femur of 1 pig per pen was collected and carcass characteristics from this pig were measured. No interactions were observed between diet formulation principle and phytase inclusion for growth performance in any phase and no differences among treatments were observed for overall growth performance. Plasma Ca and P and bone ash at the end of phase 1 were also not influenced by dietary treatments. However, on day 126, pigs fed nonphytase diets formulated based on total Ca had greater bone ash than pigs fed STTD Ca-based diets, but if phytase was used, no differences were observed between the 2 formulation principles (interaction P < 0.05). At the end of phases 2 and 3, pigs fed diets without phytase had greater (P < 0.05) plasma P than pigs fed diets with phytase, but no differences were observed at the end of phases 4 and 5. A negative quadratic effect (P < 0.05) of phase (2 to 5) on the concentration of plasma Ca was observed, whereas plasma P increased (quadratic; P < 0.05) from phases 2 to 5. However, there was no interaction or effect of diet formulation principle or phytase inclusion on any carcass characteristics measured. In conclusion, STTD Ca to STTD P ratios can be used in diet formulation for growing-finishing pigs without affecting growth performance or carcass characteristics and phytase inclusion ameliorates bone resorption caused by low dietary Ca and P.