Farmed fish are increasingly grown in intensive and semi-intensive systems where most nutrients are provided by formulated feeds. These are formulated to minimise costs and optimise growth, notably the rate of muscle protein synthesis (i.e., fillet). Protein synthesis depends on the availability of amino acids (i.e., protein) and energy. Thus, fish feeds are often formulated to provide a balanced ratio of protein to energy (P:E). Above and below the optimal dietary P:E, absorbed protein and energy are expected to be under-utilised for body protein synthesis, respectively. Estimates of the optimal dietary P:E vary largely for Nile tilapia (Oreochromis niloticus (L., 1758)). Published values range from 13 to 26 g of dietary protein per MJ of energy. Here, we challenge the idea that growth, protein utilisation efficiency and body composition can all be simultaneously optimised, when Nile tilapia are fed an optimal dietary P:E. Through linear and non-linear regression meta-analyses, we quantitatively describe the effects of protein and energy intake on nutrient partitioning, feed efficiency and growth. We find linear relationships between the dietary P:E and protein retention efficiency. The lack of an inflection contradicts the existence of an optimal P:E. Our regressions of protein and energy intake versus protein gain, indicate that protein gain is often simultaneously limited by both protein and energy intake, and may be limited by other factors than protein and energy intake, such as a maximal protein deposition capacity (PD_max). We conclude that there is no physiological basis for an optimal P:E in Nile tilapia feeds.

中文翻译：

---

平衡尼罗罗非鱼饲料中的蛋白质和能量：荟萃分析

养殖鱼类越来越多地在集约化和半集约化系统中种植，其中大部分营养物质由配方饲料提供。这些配方旨在最大限度地降低成本并优化生长，特别是肌肉蛋白质合成速率（即鱼片）。蛋白质合成取决于氨基酸（即蛋白质）和能量的可用性。因此，鱼饲料通常经过配制以提供蛋白质与能量的平衡比例 (P:E)。在最佳膳食 P:E 之上和之下，预计吸收的蛋白质和能量分别未充分用于身体蛋白质合成。尼罗罗非鱼 ( Oreochromis niloticus ) 的最佳膳食 P:E 估计值差异很大（L.，1758 年））。公布的数值范围为每 MJ 能量 13 至 26 g 膳食蛋白质。在这里，我们挑战了当尼罗罗非鱼饲喂最佳膳食 P:E 时，生长、蛋白质利用效率和身体成分都可以同时优化的想法。通过线性和非线性回归荟萃分析，我们定量描述了蛋白质和能量摄入对养分分配、饲料效率和生长的影响。我们发现膳食 P:E 和蛋白质保留效率之间存在线性关系。没有拐点与最优 P:E 的存在相矛盾。我们对蛋白质和能量摄入与蛋白质增益的回归表明，蛋白质增益通常同时受到蛋白质和能量摄入的限制，并且可能受到蛋白质和能量摄入以外的其他因素的限制，_最大）。我们得出结论，尼罗罗非鱼饲料中的最佳 P:E 没有生理基础。