This study was conducted to determine the dietary total aromatic amino acid requirement and tyrosine replacement value for phenylalanine for fingerling Oreochromis niloticus by conducting two 8-week experiments. In experiment I, phenylalanine requirement was determined by feeding test diets (350 g kg^–1 CP; 16.72 kJ g^–1 GE) with graded levels of phenylalanine (4, 6.5, 9, 11.5, 14 and 16.5 g kg^–1 dry diet) at a constant level (10 g kg^–1) of dietary tyrosine to triplicate groups of fish (1.65 ± 0.09 g). Quadratic analyses of absolute weight gain (AWG), protein deposition (PD%) and phenylalanine retention efficiency (PRE%) indicated the requirement at 12.1 g kg^–1 dry diet. In experiment II, six diets with different levels of L-tyrosine (2.0, 4.0, 6.0, 8.0, 10.0 and 12.0 g kg^–1 dry diet) with 12.1 g kg^–1 phenylalanine as determined in experiment I fixed in all the test diets were fed to fish (1.67 ± 0.17 g) to determine the tyrosine requirement under same conditions. Quadratic regression analysis of AWG, PD and PRE demonstrated the tyrosine requirement at 8.5 g kg^–1 dry diet, corresponding to 24.2 g kg^–1 of dietary protein. Based on the above data, the total aromatic amino acid requirement was found to be 20.6 g kg^–1 of dry diet, corresponding to 58.8 g kg^–1 of dietary protein, and tyrosine replacement value for phenylalanine was found to be 37% on a molar basis.

中文翻译：

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Oreochromis niloticus (Linnaeus) 鱼种的膳食总芳香族氨基酸需求和苯丙氨酸的酪氨酸替代值

本研究旨在通过进行两个为期 8 周的实验来确定尼罗罗非鱼鱼种的日粮总芳香族氨基酸需求和苯丙氨酸的酪氨酸替代值。在实验 I 中，苯丙氨酸需要​​量通过饲喂试验日粮（350 g kg ^–1 CP；16.72 kJ g ^–1 GE）和苯丙氨酸分级水平（4、6.5、9、11.5、14 和 16.5 g kg ^–1干日粮）来确定) 以恒定水平 (10 g kg ^–1 ) 的膳食酪氨酸对三组鱼 (1.65 ± 0.09 g) 进行试验。绝对增重 (AWG)、蛋白质沉积 (PD%) 和苯丙氨酸保留效率 (PRE%) 的二次分析表明要求为 12.1 g kg ^–1干饮食。在实验二中，六种含有不同水平 L-酪氨酸的日粮（2.0、4.0、6.0、8.0、10.0 和 12.0 g kg ^–1干日粮）和 12.1 g kg ^–1苯丙氨酸（如试验 I 中确定的）固定在所有试验日粮中被喂给鱼 (1.67 ± 0.17 g) 以确定在相同条件下的酪氨酸需求。AWG、PD 和 PRE 的二次回归分析表明，8.5 g kg ^–1干日粮需要酪氨酸，相当于 24.2 g kg ^–1日粮蛋白质。根据上述数据，发现干粮的总芳香族氨基酸需要量为 20.6 g kg ^–1，相当于 58.8 g kg ^–1 膳食蛋白质的含量，苯丙氨酸的酪氨酸替代值以摩尔计为 37%。