Dietary α-lipoic acid supplementation to improve growth, blood chemistry, and liver antioxidant status of African catfish Clarias gariepinus

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.