Department of Food and Human Nutritional Sciences, University of Manitoba, Winnipeg, MB, R3T 2N2, Canada.
Department of Animal Science, University of Manitoba, Winnipeg, MB, R3T 2N2, Canada.
Poult Sci. 2018 Jul 1;97(7):2400-2410. doi: 10.3382/ps/pey057.
The oversupply of dietary phosphorus (P) leads to increased feed costs and discharge of excessive P to the environment, thus directly impacting the sustainability of egg production practices. The present study was conducted to better define the minimal available P needs of laying hens. Fifty-six Lohmann white laying hens were individually caged and fed one of 7 diets with graded levels of available P (0.15, 0.20, 0.25, 0.30, 0.35, 0.40, or 0.45%) for 12 weeks. Records were maintained for body weight, feed intake, and egg production during the experimental period. Blood and egg samples were collected and digestibility studies conducted at wk 6 and 12 of the experiment. At the end of the experiment, tibia characteristics and expression of the P transporters in the small intestine and kidney were determined. Lowering dietary available P from 0.45 to 0.15% generally reduced plasma P concentrations (P < 0.01), but hen productive performance, plasma calcium, parathyroid hormone and other constituents, tibia bone mineral density and content, tibia ash percentage, and mRNA abundance of the small intestine, and kidney type II sodium/phosphate cotransporter were not different among treatments. Specific gravity and eggshell thickness tended to increase with reducing dietary P (P < 0.05). Total P intake, excretion, and retention net amount decreased (P < 0.01) with reducing dietary P, but its retention rate (of intake) remained unchanged. Furthermore, changing dietary P did not affect calcium retention rate and net deposition of total P and calcium in eggs. These data indicate that reducing dietary available P up to 0.15% is adequate to maintain health and performance of layers. As such, this minimal available P estimate should serve as a benchmark for the assessment of P contents of commercial laying hen rations, with the goal of enhancing the sustainability of egg production.
日粮中磷（P）的过量供应会增加饲料成本，并将过量的 P 排放到环境中，从而直接影响蛋鸡生产实践的可持续性。本研究旨在更好地确定产蛋鸡最低可利用 P 需要量。将 56 只罗曼白产蛋鸡单独饲养在笼中，饲喂 7 种不同可利用 P 水平（0.15、0.20、0.25、0.30、0.35、0.40 或 0.45%）的日粮 12 周。在实验期间，记录体质量、采食量和产蛋量。在实验的第 6 和第 12 周采集血样和蛋样，并进行消化率研究。实验结束时，测定胫骨特性和小肠及肾脏 P 转运体的表达。与 0.45%可利用 P 日粮相比，降低日粮可利用 P 水平至 0.15%通常会降低血浆 P 浓度（P＜0.01），但母鸡生产性能、血浆钙、甲状旁腺激素和其他成分、胫骨骨密度和含量、胫骨灰分百分比以及小肠和肾脏 2 型钠/磷酸盐协同转运蛋白的 mRNA 丰度在处理间没有差异。比重和蛋壳厚度随着降低日粮 P 而趋于增加（P＜0.05）。随着日粮 P 的降低，总 P 摄入量、排泄量和保留净量减少（P＜0.01），但保留率（摄入量的保留率）保持不变。此外，改变日粮 P 对钙保留率和总 P 和钙在蛋中的净沉积没有影响。这些数据表明，将日粮可利用 P 降低至 0.15%足以维持蛋鸡的健康和生产性能。因此，该最低可利用 P 估计值应作为评估商业产蛋鸡日粮 P 含量的基准，以提高蛋鸡生产的可持续性。
