This study aimed to evaluate the effect of dietary supplementation of α-lipoic acid (LA) in the growth, blood chemistry, and liver antioxidant status of African catfish Clarias gariepinus. This study applied a completely randomised experimental design consisting of five experimental diets (30% protein and 4% lipid) with graded levels of LA, i.e. LA0.0 as the control (0.0 g LA kg⁻¹ feed), LA0.5 (0.5g LA kg⁻¹ feed), LA1.0 (1.0 g LA kg⁻¹ feed), LA1.5 (1.5 g LA kg⁻¹ feed), and LA2.0 (2.0 g kg⁻¹ feed) with three replications. An orthogonal polynomial regression analysis was used to determine the optimum dose of LA for fish growth. Seventy-five catfish juveniles (14.65±0.05 g) were randomly distributed into each fibre tank (600 L in capacity) and maintained in zero water exchange condition for 60 days. The fish were fed twice a day to apparent satiation at 08.00 AM and 05.00 PM (GMT+7). Fish survival was at a range of 93.78–97.78% and was not significantly different amongst the treatments (P>0.05). The final body weight, biomass and specific growth rate of the fish fed with LA supplemented diets were generally higher than those of the control. Higher feed intake and feed protein retention were also higher in LA treatment groups compared to that of the control, but there were no significant differences in the feed conversion ratio. In the present study, visual observation on the liver colour was used to indicate the liver condition. Abnormal coloured fish liver (pale coloured) was found to be higher in lipid and malondialdehyde, and lower in superoxide dismutase (SOD) activity than those of normal coloured (red coloured) liver. The percentage of normal coloured liver (red coloured liver) in the control (28.8 %) was lower than that of the LA treatment groups (46.7–70 %). Antioxidant status of the fish in LA treatment groups was superior than that of the control as indicated by the lower levels of MDA and the higher SOD activities. Regardless of the dose of LA, all fish fed on LA supplemented diets demonstrated significantly lower plasma alanine aminotransferase and aspartate aminotransferase levels than those of the control (P<0.05). The fish in LA0.5, LA1.0, and LA1.5 treatments had significantly lower cholesterol and low-density lipoprotein (LDL) and higher high-density lipoprotein (HDL) levels compared to the control and LA2.0 group (P<0.05). In conclusion, the present study demonstrated that dietary supplementation of LA could enhance the growth, blood chemistry, and liver antioxidant status of African catfish juveniles. Based on the polynomial orthogonal analyses, an LA dietary supplementation level of 1.21 g kg⁻¹ feed can be recommended for optimum growth of African catfish.

本研究旨在评估日粮中添加 α-硫辛酸 (LA) 对非洲鲶鱼Clarias gariepinus的生长、血液化学和肝脏抗氧化状态的影响。本研究采用完全随机的实验设计，由五种实验饮食（30% 蛋白质和 4% 脂质）组成，具有分级的 LA 水平，即 LA0.0 作为对照（0.0 g LA kg ^-1饲料），LA0.5（0.5 g LA kg ^-1饲料）、LA1.0（1.0 g LA kg ^-1饲料）、LA1.5（1.5 g LA kg ^-1饲料）和 LA2.0（2.0 g kg ^-1饲料）饲料）三个重复。正交多项式回归分析用于确定鱼生长的最佳 LA 剂量。将 75 条鲶鱼幼鱼（14.65±0.05 g）随机分配到每个纤维槽（容量 600 L）中，并在零换水条件下保持 60 天。每天早上 8 点和下午 5 点（格林威治标准时间 + 7）喂鱼两次以达到明显的饱腹感。鱼的存活率在 93.78-97.78% 的范围内，并且在处理之间没有显着差异（P>0.05）。饲喂 LA 补充日粮的鱼的最终体重、生物量和比生长率普遍高于对照组。与对照组相比，LA 处理组的采食量和饲料蛋白质保留率也更高，但饲料转化率没有显着差异。在本研究中，通过肉眼观察肝脏颜色来指示肝脏状况。发现异常有色鱼肝（浅色）的脂质和丙二醛含量高于正常有色（红色）肝脏，而超氧化物歧化酶 (SOD) 活性较低。对照组中正常有色肝脏（红色肝脏）的百分比（28.8%）低于 LA 治疗组（46.7-70%）。LA 处理组鱼的抗氧化状态优于对照组，MDA 水平较低，SOD 活性较高。无论 LA 的剂量如何，所有以 LA 补充饲料喂养的鱼的血浆丙氨酸转氨酶和天冬氨酸转氨酶水平均显着低于对照组。P <0.05）。与对照组和LA2.0组相比，LA0.5、LA1.0和LA1.5处理的鱼胆固醇和低密度脂蛋白（LDL）显着降低，高密度脂蛋白（HDL）水平显着升高（P < 0.05）。总之，本研究表明，膳食补充剂 LA 可以增强非洲鲶鱼幼鱼的生长、血液化学和肝脏抗氧化状态。根据多项式正交分析，可以推荐1.21 g kg ^-1饲料的 LA 日粮添加水平以实现非洲鲶鱼的最佳生长。