Monogastric Research Centre, School of Agriculture and Environment, Massey University, Palmerston North 4442, New Zealand.
Monogastric Research Centre, School of Agriculture and Environment, Massey University, Palmerston North 4442, New Zealand.
Poult Sci. 2022 Nov;101(11):102135. doi: 10.1016/j.psj.2022.102135. Epub 2022 Aug 19.
An experiment was conducted to determine the digestible calcium (Ca) and digestible phosphorous (P) requirements of 11 to 24 d old broiler chickens. Eighteen corn-soybean meal-based diets containing 1.80, 2.35, 2.90, 3.45, 4.00, and 4.55 g/kg standardized ileal digestible (SID) Ca and 3.5, 4.5, and 5.5 g/kg SID P were fed to broilers from d 11 to 24. Each experimental diet was randomly allocated to six replicate cages (8 birds per cage). Body weight and feed amount were recorded at the start and end of the experiment and the feed conversion ratio was calculated. On d 24, birds were euthanized to collect ileal digesta, tibia, and carcass for the determination of digestible Ca and P, the concentration of ash, Ca and P in tibia and the retention of Ca and P in the carcass, respectively. Titanium dioxide (5 g/kg) was included in all diets as an indigestible indicator for apparent ileal digestibility measurement. Total excreta output was measured during the last 4 d of the experimental period for the measurement of apparent total tract retention of Ca and P. Fixed effects of the experiment were dietary concentrations of SID Ca and SID P and their interaction. If the interaction or main effect was significant (P < 0.05), the parameter estimate for second-order response surface model was determined using General Linear Model procedure of SAS. The weight gain of broiler growers was optimized at the SID P concentration of 3.5 g/kg and SID Ca concentrations between 2.35 and 4.00 g/kg. At 3.5 g/kg SID P concentration, the required SID Ca for maximum weight gain was determined to be 3.05 g/kg, which corresponded to SID Ca to SID P ratios of 0.87. The concentration of SID Ca that maximized tibia ash at 3.5 g/kg SID P was 3.69 g/kg, which corresponded to SID Ca to SID P ratio of 1.05. Maximizing bone ash requires more Ca than maximizing weight gain. Carcass Ca and P retention were reflective of total tract Ca and P retention values. The estimated SID Ca requirements (at 3.5 g/kg SID P) for both maximized weight gain (3.05 g/kg or 6.11 g/kg total Ca) and bone ash (3.69 g/kg or 7.28 g/kg total Ca) are lower than the current Ca recommendation (8.70 g/kg total Ca equivalent to 4.03 g/kg SID Ca; Ross, 2019) for broiler growers, indicating possible oversupply of Ca in diets formulated based on the current recommendation.
进行了一项实验，以确定 11 至 24 日龄肉鸡的可消化钙（Ca）和可消化磷（P）需求。18 种基于玉米-豆粕的饲粮含有 1.80、2.35、2.90、3.45、4.00 和 4.55 g/kg 标准回肠可消化（SID）Ca 和 3.5、4.5 和 5.5 g/kg SID P，从第 11 天到第 24 天喂给肉鸡。每个实验饲粮随机分配到 6 个重复笼（每个笼 8 只鸡）。在实验开始和结束时记录体重和饲料量，并计算饲料转化率。在第 24 天，对鸟类进行安乐死，以收集回肠内容物、胫骨和胴体，分别用于测定可消化 Ca 和 P、灰分浓度、胫骨中 Ca 和 P 浓度以及胴体中 Ca 和 P 的保留量。所有饲粮中均添加了二氧化钛（5 g/kg）作为不可消化的指示剂，用于测量表观回肠消化率。在实验的最后 4 天测量总排泄物产量，以测量 Ca 和 P 的表观全肠道保留量。实验的固定效应为 SID Ca 和 SID P 的饲粮浓度及其相互作用。如果相互作用或主效应显著（P < 0.05），则使用 SAS 的 General Linear Model 程序确定二阶响应面模型的参数估计值。肉鸡生长者的体重增加在 SID P 浓度为 3.5 g/kg 和 SID Ca 浓度在 2.35 至 4.00 g/kg 之间达到最佳。在 3.5 g/kg SID P 浓度下，确定最大体重增加所需的 SID Ca 为 3.05 g/kg，这对应于 SID Ca 与 SID P 的比例为 0.87。在 3.5 g/kg SID P 浓度下，最大胫骨灰分所需的 SID Ca 为 3.69 g/kg，这对应于 SID Ca 与 SID P 的比例为 1.05。最大限度地增加骨灰分需要比最大限度地增加体重更多的 Ca。胴体 Ca 和 P 保留反映了总肠道 Ca 和 P 保留值。估计的 SID Ca 需求（在 3.5 g/kg SID P 时），同时达到最大体重增加（3.05 g/kg 或 6.11 g/kg 总 Ca）和骨灰分（3.69 g/kg 或 7.28 g/kg 总 Ca），低于当前肉鸡生长者的 Ca 推荐量（8.70 g/kg 总 Ca 相当于 4.03 g/kg SID Ca；Ross，2019），表明基于当前推荐配方的饲粮中可能存在 Ca 供应过剩。
