Threonine is an essential amino acid in fish nutrition, but no information is available on the dietary threonine requirement in largemouth bass, Micropterus salmoides. Thus, 360 fish (19.0 ± 0.1 g) were randomly divided into six experimental groups (20 fish per cage; three replicates), and offered diets supplemented with crystalline L-threonine at 0 g kg⁻¹ (control), 2.5 g kg⁻¹ (Thr-2.5), 5.0 g kg⁻¹ (Thr-5.0), 7.5 g kg⁻¹ (Thr-7.5), 10.0 g kg⁻¹ (Thr-10.0) and 12.5 g kg⁻¹ (Thr-12.5) for eight weeks to determine the optimum threonine requirement of largemouth bass. The results showed that dietary threonine significantly (P < 0.05) influenced final body weight, weight gain, specific growth rate, feed conversion ratio, protein efficiency ratio, protein retention efficiency and lipid retention efficiency of largemouth bass. Weight gain and specific growth rate increased firstly, then decreased with the increasing threonine supplementation. Thr-5.0 group had the highest weight gain (267%) and the lowest FCR (0.76) among all groups. Body indices such as hepatosomatic index, viscerosomatic index and condition factor were not affected (P > 0.05) by any dietary treatments. Whole-body crude protein and lipid were lower (P < 0.05) in fish fed threonine-supplemented diets than the control group, although those contents were higher in muscle. Monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs) in fish muscle were also significantly (P < 0.05) modulated by threonine supplementation. Overall, threonine had a positive impact on most of the above mentioned parameters of largemouth bass, and the optimum level of supplemental threonine that maximized fish growth and feed utilization was 5.0 g kg⁻¹ (Thr-5.0), corresponding to 14.3 g kg⁻¹ dietary threonine.

苏氨酸是鱼类营养中必不可少的氨基酸，但尚无有关大嘴鲈鱼（Micropterus salmoides）饮食中苏氨酸需求量的信息。在0克公斤，并提供补充有结晶的L-苏氨酸的饮食;因此，鱼360（19.0±0.1克），随机分为6个实验组（三个重复每笼20鱼）^-1（对照），将2.5g公斤^{- 1}（Thr-2.5），5.0 g kg ^-1（Thr-5.0），7.5 g kg ^-1（Thr-7.5），10.0 g kg ^-1（Thr-10.0）和12.5 g kg ^-1（Thr-12.5）持续八周，以确定大嘴鲈的最佳苏氨酸需求量。结果表明，饮食中苏氨酸含量显着（P <0.05）影响了大嘴鲈的最终体重，体重增加，比生长率，饲料转化率，蛋白质效率比，蛋白质保留效率和脂质保留效率。随着苏氨酸的添加，体重增加和比生长率先增加，然后减少。在所有组中，Thr-5.0组的体重增加最高（267％），FCR最低（0.76）。 饮食疗法对人体指标如肝体指数，内脏体指数和条件因子均无影响（P > 0.05）。全身粗蛋白和脂质较低（P 用苏氨酸补充饮食的鱼比对照组中的<0.05），尽管这些含量在肌肉中较高。鱼肉中的单不饱和脂肪酸（MUFAs）和多不饱和脂肪酸（PUFAs）也受到苏氨酸补充的显着调节（P <0.05）。总体而言，苏氨酸具有高于鲈鱼的提到的参数对大多数的积极的影响，和的最佳水平补充苏氨酸，最大限度地鱼的生长和饲料利用率为5.0g千克^-1（THR-5.0），对应于14.3克公斤^{- 1}饮食苏氨酸。