Arginine (Arg) is an important essential amino acid required for optimum fish growth. However, its role in plant-rich diets on growth and the required level in juvenile Hemibagrus wyckioides are currently unknown. This study evaluated the effects of Arg supplementation in plant-rich diets on growth, feed utilization, whole body composition, blood biochemical indicators and gene expressions of the target of rapamycin (TOR) signaling pathway in juvenile H. wyckioides. A total of 450 fish (6.40 ± 0.06 g) were randomized into six equal groups and fed on diets with graded Arg levels: 0 (control), 3, 6, 9, 12 and 15 g/kg of dry feed for eight weeks. The results revealed that specific growth rate (SGR) and feed conversion ratio of juvenile H. wyckioides were significantly improved and reduced, respectively in fish fed on 9 g/kg of Arg supplementation (p < .05). The optimum amount of dietary Arg content in plant-rich diets for H. wyckioides was 63.77 g/kg diet based on SGR. Feeding fish with dietary Arg supplementation ranging from 9 to 12 g/kg improved significantly (p < .05) whole body protein contents and decreased lipid deposition. The mRNA levels of TOR, eukaryotic translation initiation factor 4E (4EBP) and ribosomal protein S6 kinase 1 (S6K1) in muscle and liver were significantly affected by increasing dietary Arg levels. Meanwhile, the mRNA relative expression levels of TOR and S6K1 in the liver and muscle increased significantly as Arg supplementation increased. On the other hand, the mRNA relative expression levels of 4EBP was significantly higher in fish fed on the 9 g/kg Arg diet compared to those fed on the control and 15 g/kg Arg diets. In conclusion, our current results indicate that dietary Arg supplementation in plant-rich diets, might activate the TOR signaling pathway, which promotes protein synthesis and reduces lipid accumulation of H. wyckioides, resulting in improved growth.

中文翻译：

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植物性日粮中添加精氨酸对亚洲红尾鲇幼鱼（Hemibagrus wyckoiides）生长、饲料利用率、体成分、血液生化指标和雷帕霉素信号通路靶标基因表达的影响

精氨酸 (Arg) 是鱼类最佳生长所需的重要必需氨基酸。然而，目前尚不清楚其在富含植物的饮食中对生长的作用以及幼体Hemibagrus wyckioides所需的水平。本研究评估了在富含植物的日粮中添加 Arg 对Wyckioides幼鱼生长、饲料利用率、全身组成、血液生化指标和雷帕霉素 (TOR) 信号通路靶标基因表达的影响。总共 450 条鱼 (6.40 ± 0.06 g) 被随机分成六个相等的组，并以 Arg 水平分级的饲料喂养：0（对照）、3、6、9、12 和 15 g/kg 干饲料，持续 8 周。研究结果表明，金鱼草幼鱼的比生长率（SGR）和饲料转化率在补充 9 g/kg Arg 的鱼中，鱼的差异分别显着改善和减少 ( p  < .05)。基于 SGR的H. wyckioides富含植物的日粮中 Arg 的最佳含量为63.77 g/kg 日粮。饲料中添加 9 至 12 g/kg 的 Arg 可显着改善鱼（p < .05) 全身蛋白质含量和脂质沉积减少。肌肉和肝脏中 TOR、真核翻译起始因子 4E (4EBP) 和核糖体蛋白 S6 激酶 1 (S6K1) 的 mRNA 水平受到饮食精氨酸水平增加的显着影响。同时，随着Arg补充的增加，肝脏和肌肉中TOR和S6K1的mRNA相对表达水平显着增加。另一方面，与对照组和 15 g/kg Arg 饮食相比，饲喂 9 g/kg Arg 饮食的鱼中 4EBP 的 mRNA 相对表达水平显着更高。总之，我们目前的研究结果表明，在富含植物的饮食中补充精氨酸可能会激活 TOR 信号通路，从而促进蛋白质合成并减少H. wyckioides的脂质积累，从而改善生长。