Introduction
Coenzyme Q10 (CoQ10), known as ubiquinone, is a coenzyme that functions as an electron transporter in the ATP production. CoQ10 acts as an antioxidant with sparing effect for vitamin C and E. Micelle structures possess an interface between hydrophilic and hydrophobic area, which can protect feed additives and facilitate their absorption in the body . Olive flounder (P. olivaceus ) is the main aquaculture species in South Korea. This study was conducted to evaluate dietary CoQ10 and micelle form C oQ10 (MCoQ10) supplementations in diet for olive flounder feed.
Materials and methods
A basal diet (Con) was formulated to contain 600 g/kg fish meal and 120 g/kg soybean meal as main protein sources. Seven o ther diets were prepared adding 20 and 40 mg CoQ10/kg (CQ2 and CQ4, respectively), and 10, 20, 40, 80 and 160 mg MCoQ10/kg (MQ1, MQ2, MQ4, MQ8 and MQ16, respectively). Experimental fish ( initial mean body weight: 24.1 g) were randomly distributed into 24 tanks (300 L), with 30 fish per tank in triplicates , and fed the diets twice daily for a 66-day feeding trial. At the e nd of feeding trial , all fish were individually counted . To test the disease resistance against Edwardsiella tarda , the remaining fish were re-distributed into 24 acrylic tanks (120 L) with 12 fish per tank in triplicates. Each fish was injected with 100 μL of 1.0×107 CFU/mL E. tarda suspension (5.0×104 CFU/fish). Mortality was monitored at 6- h intervals for 8 days (186 h).
Results
The final mean body weight and protein efficiency ratio were significantly higher in MQ4 and MQ8 groups compared to those in Con group. Ig level and lysozyme activity were significantly enhanced in all CQ and MQ groups. Anti-protease and phagocytic activities in MQ2, MQ4, MQ8 and MQ16 groups were significantly higher than in Con group. Antioxidant capacities (superoxide dismutase, glutathione peroxidase and catalase) were significantly improved in fish fed MQ2, MQ4 and MQ8 diets than in fish fed Con diet. Lipase activity was significantly increased in all CQ and MQ supplemented groups. Chymotrypsin and trypsin activities were significantly improved in CQ4, MQ8 and MQ16 groups compared to Con group. Intestine villi length, villi width and goblet cell counts were significantly increased in all CQ and MQ groups compared to Con group. Expression of inflammation-related genes were upregulated in CQ2, MQ1, MQ2, MQ4, MQ8 and MQ16 groups than in Con group. CoQ10 levels in l iver and muscle were significantly higher in CQ4, MQ4, MQ8 and MQ16 groups than that in Con group. Vitamin C levels in liver and muscle were increased in MQ2 and MQ4 groups. Vitamin E levels in l iver and m uscle were the highest in MQ4 group. For intestinal microbiota, MQ8 and MQ16 groups showed significantly higher proportion of lactic acid bacteria, while all CQ and MQ groups exhibited lower proportions of Vibrio bacteria compared to Con group . Following the 186-h E. tarda challenge test, cumulative survival of all CQ and MQ groups were significantly higher than that of Con group.
Conclusion
This study suggests that MCoQ10 supplementation could enhance growth performance, immune response , antioxidant capacity, intestinal microbiota and disease resistance against E. tarda . T he optimal dietary supplementation level of MCoQ10 in diet for olive flounder is likely to be 40-80 mg/kg.