Neuroendocrine Unit, Medizinische Klinik Innenstadt, Ludwig-Maximilians University, Munich, Germany.
Br J Nutr. 2010 May;103(10):1525-33. doi: 10.1017/S000711450999345X. Epub 2010 Jan 5.
Knowledge about metabolisable energy (ME) intake is crucial for various experimental settings in rodent studies. ME considers faecal and renal energy losses. In particular, faecal energy excretion can vary considerably between differentially composed diets. Thus determination of faecal energy losses, i.e. apparent energy digestibility, is the most important experimental approach to determine ME. Predictive equations for ME such as Atwater factors or an equation for pigs, which are frequently employed for rodent feed, consider an average energy digestibility for nutrients and average renal losses for protein. Both equations, however, were never validated for rat feed. We therefore determined experimentally the digestibility of energy (experimentally determined digestible energy - 5.2 kJ/g digestible protein) and nutrients of eleven natural and five purified rat diets and compared the present results with the predicted values. Compared with natural diets, digestibility of gross energy (GE) and nutrients was higher by about 20 % in the purified diets (P < 0.0001). Mean GE digestibility in natural diets amounted to 71.4 % (range 53.3-83.5 %; n 11). Atwater factors predicted ME with satisfactory accuracy in purified diets. In contrast, for natural diets, only the equation for pig feed gave acceptable estimates of ME. Choosing an inappropriate predictive equation for ME resulted in considerable error. For prediction of ME in mixed rat feed, we propose to use the equation for pig feed for natural diets and Atwater factors for purified diets. If the equation for pig feed cannot be applied we suggest using the lower modified Atwater factors instead of the 'original' Atwater factors to estimate the ME of a diet.
关于代谢能（ME）摄入量的知识对于啮齿动物研究中的各种实验设置至关重要。ME 考虑了粪便和肾脏的能量损失。特别是，不同组成的饮食之间粪便能量排泄量可能有很大差异。因此，确定粪便能量损失，即表观能量消化率，是确定 ME 的最重要的实验方法。常用于啮齿动物饲料的 ME 预测方程，如阿特沃特因子或猪的方程，考虑了营养素的平均能量消化率和蛋白质的平均肾脏损失。然而，这两个方程都从未在大鼠饲料中得到验证。因此，我们通过实验确定了 11 种天然和 5 种纯化大鼠饲料的能量（实验确定的可消化能量-5.2 kJ/g 可消化蛋白）和营养素的消化率，并将目前的结果与预测值进行了比较。与天然饮食相比，纯化饮食中总能量（GE）和营养素的消化率高约 20%（P < 0.0001）。天然饮食中 GE 的平均消化率为 71.4%（范围 53.3-83.5%；n=11）。阿特沃特因子在纯化饮食中对 ME 的预测具有令人满意的准确性。相比之下，对于天然饮食，只有猪饲料方程才能给出 ME 的可接受估计。选择不适当的 ME 预测方程会导致相当大的误差。对于混合大鼠饲料的 ME 预测，我们建议对天然饮食使用猪饲料方程，对纯化饮食使用阿特沃特因子。如果不能应用猪饲料方程，我们建议使用修改后的较低阿特沃特因子代替“原始”阿特沃特因子来估计饮食的 ME。
