Synergism of Dietary Co-Supplementation with Lutein and Bile Salts Improved the Growth Performance, Carotenoid Content, Antioxidant Capacity, Lipid Metabolism, and Lipase Activity of the Marbled Spinefoot Rabbitfish, Siganus rivulatus

SIMPLE SUMMARY: In the natural aquatic environment, fish obtain their carotenoid requirements from the natural food web. Meanwhile, under aquaculture conditions, especially intensive culture, fish are deprived in terms of their carotenoids requirements from the environment. Accordingly, the artificial diet formula must consider the carotenoids accessibility and maintain its efficient utilization. Moreover, in fish larvae, the absorption of carotenoids as lutein (LTN) is not efficient. Therefore, as LTN is fat-soluble carotenoid, the improvement of fat digestion and absorption could improve LTN utilization. The present work evaluated the effect of individual or co-supplementation of LTN and bile salts (BS) in the diets of rabbitfish (Siganus rivulatus) larvae. The results revealed an improvement of growth performance and survival (%) with dietary supplementation with LTN and BS, which could enhance the cost–benefit of farming rabbitfish. Also, the carotenoid deposition, antioxidant status, lipase activity, and lipid metabolism improved with co-supplementation of LTN and BS than its individual supplementation. ABSTRACT: A 60-day feeding trial was conducted to assess the effects of dietary supplementation with bile salts (BS), lutein (LTN), and their combination on growth, survival, carotenoid content, and antioxidant status of rabbitfish (Siganus rivulatus) larvae. Fish were fed four isonitrogenous (34.39% protein) and isoenergetic (20.57 kJ/g) diets supplemented with BS (0.15 g kg(−1)), LTN (0.1 g kg(−1)), BS+LTN (0.15 and 0.1 g kg(−1), respectively), and a non-supplemented control diet. The results revealed that fish fed BS+LTN had the highest significant specific growth rate (4.37% day(−1)), feed efficiency (46.55%), and survival (97.78%). Lutein supplementation improved whole-body protein content, meanwhile, fish fed a BS-supplemented diet had a higher lipid content. The carotenoid deposition was significantly increased with LTN and BS+LTN in skin, muscle, and whole body compared to the control and BS treatment. All dietary supplementation of BS and LTN showed significant improvement in total antioxidant capacity, catalase, and glutathione peroxidase activities. Additionally, LTN alone or BS+LTN significantly reduced malondialdehyde levels by 5.30 and 29.91%, respectively compared to the control. BS supplementation modulated aminopeptidases activities, triglycerides, cholesterol, and increased the activity of pancreatic lipase. Therefore, it could be inferred that dietary supplementation with LTN in combination with BS could improve the growth performance, carotenoid deposition, antioxidant status, lipid digestion, and metabolism of S. rivulatus.