Schulin-Zeuthen M, Kebreab E, Gerrits W J J, Lopez S, Fan M Z, Dias R S, France J
Centre for Nutrition Modelling, Department of Animal and Poultry Science, University of Guelph, Ontario, N1G 2W1, Canada.
J Anim Sci. 2007 Aug;85(8):1953-61. doi: 10.2527/jas.2006-715. Epub 2007 Apr 27.
Many studies have highlighted concerns over current methods of determining endogenous P losses and P requirements in growing pigs. Therefore, a database containing observations on 350 pigs was assembled from various studies. Four functions for analyzing P balance data were considered: 1) a straight line, 2) a diminishing returns function (monomolecular), 3) a sigmoidal function with a fixed point of inflection (Gompertz), and 4) a sigmoidal function with a flexible point of inflection (Richards). The nonlinear functions were specifically reparameterized to assign biological meaning to the parameters. Meta-analysis of the data was conducted to estimate endogenous P excretion, maintenance requirement, and efficiency of utilization. Phosphorus retention was regressed against either available P intake or total P intake [all variables scaled by metabolic BW (BW(0.75))]. There was evidence of non-linearity in the data, and the monomolecular function provided the best fit to the data. The Richards equation did not fit the data well and appeared overparameterized. Estimates of endogenous P excretion of 14 and 17 mg/kg of BW(0.75) x d based on available and total P analysis, respectively, were predicted by the monomolecular equation, which were within the range reported in the literature. Maintenance requirement values of 15 mg of available P/kg of BW(0.75) x d and 37 mg of total P/kg of BW(0.75) x d were obtained, based on the monomolecular equation. Average efficiencies of conversion of dietary P to retained P were 65 and 36% for available and total P, respectively, with greater efficiency values calculated for low P intakes. Although the monomolecular equation fitted the data best, more observations at high P intakes/kg of BW(0.75) are required to determine conclusively whether P retention scaled by metabolic BW is linearly related to available or total P intake.
许多研究都强调了对当前测定生长猪内源性磷损失和磷需求量方法的担忧。因此，从各项研究中收集了一个包含350头猪观测数据的数据库。考虑了四种分析磷平衡数据的函数：1）直线函数，2）收益递减函数（单分子函数），3）具有固定拐点的S形函数（冈珀茨函数），4）具有灵活拐点的S形函数（理查兹函数）。对非线性函数进行了专门的重新参数化，以便为参数赋予生物学意义。对数据进行了荟萃分析，以估计内源性磷排泄量、维持需求量和利用率。磷潴留量与可利用磷摄入量或总磷摄入量进行回归分析[所有变量均按代谢体重（BW(0.75)）进行缩放]。数据存在非线性的证据，单分子函数对数据的拟合效果最佳。理查兹方程对数据拟合不佳，且似乎参数过多。单分子方程预测，基于可利用磷和总磷分析，内源性磷排泄量分别为14和17毫克/千克BW(0.75)×天，这在文献报道的范围内。基于单分子方程，可获得维持需求量值分别为15毫克可利用磷/千克BW(0.75)×天和37毫克总磷/千克BW(0.75)×天。日粮磷转化为潴留磷的平均效率，可利用磷和总磷分别为65%和36%，低磷摄入量时计算出的效率值更高。尽管单分子方程对数据拟合最佳，但需要更多每千克BW(0.75)高磷摄入量时的观测数据，才能最终确定按代谢体重缩放的磷潴留量与可利用磷或总磷摄入量是否呈线性相关。
