The effects of dietary Nano selenium (Se) and garlic extract on the performance of grass carp under different stocking densities were examined. Fish (2.10 ± 0.09 g) were stocked into 18 tanks: fish were fed a diet supplemented with 1 mg Nano Se and 1 g garlic kg⁻¹ diet (Diet1) or a diet supplemented with 2 mg Nano Se and 2 g garlic kg⁻¹ diet (Diet2) and reared at low (LD, 24 fish per tank), medium (MD, 48 fish per tank), and high (HD, 96 fish per tank) stocking densities. After 60 days, growth was highest in Diet2-LD and Diet2-MD groups and lowest in Diet1-HD group. Results showed an extreme low or high density induced stress responses. At all densities, serum cortisol and glucose levels were significantly lower and amylase and lipase activities were higher in fish fed diet 2. The protease, catalase, and GPx activities were highest in the Diet2-MD group. The highest SOD activity was observed in medium-density groups. The serum malondialdehyde level was lowest in Diet2-LD and Diet2-MD groups. Thus, higher dietary levels of Nano Se and garlic are recommended to suppress stress and improve growth, digestive activity, and antioxidant capacity in grass carp. In addition, farming fish at medium density is the most optimal aquaculture practice.

中文翻译：

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饲养密度和日粮添加纳米硒和大蒜提取物对草鱼生长、饲料利用、消化酶、应激反应和抗氧化能力的交互作用

研究了日粮纳米硒 (Se) 和大蒜提取物对不同放养密度下草鱼性能的影响。将鱼 (2.10 ± 0.09 g) 放入 18 个鱼缸：饲喂添加了 1 mg Nano Se 和 1 g 大蒜 kg ^{-1 的}日粮（Diet1）或添加了 2 mg Nano Se 和 2 g 大蒜 kg ^-的日粮^{。 1}饮食 (Diet2) 并以低（LD，每箱 24 条鱼）、中（MD，每箱 48 条鱼）和高（HD，每箱 96 条鱼）放养密度饲养。60 天后，Diet2-LD 和 Diet2-MD 组的生长最高，Diet1-HD 组的生长最低。结果显示极低或高密度引起的应力反应。在所有密度下，饲喂饮食 2 的鱼的血清皮质醇和葡萄糖水平显着降低，淀粉酶和脂肪酶活性更高。饮食 2-MD 组的蛋白酶、过氧化氢酶和 GPx 活性最高。在中等密度组中观察到最高的 SOD 活性。血清丙二醛水平在 Diet2-LD 和 Diet2-MD 组中最低。因此，建议在饲料中添加更高水平的纳米硒和大蒜，以抑制草鱼的压力并改善其生长、消化活动和抗氧化能力。此外，