Vitamin D impacts on the intestinal health, immune status and metabolism in turbot (Scophthalmus maximus L.)

Abstract

Vitamin D (VD) plays a vital role in various physiological processes in addition to its classic functions on maintaining the balance of Ca and P metabolism. However, there still are gaps to understand in depth the issues on the precise requirement, metabolic processes and physiological functions of VD in fish. In this study, we investigated the effects of VD on the growth, intestinal health, host immunity and metabolism in turbot (Scophthalmus maximus L.), one important commercial carnivorous fish in aquaculture, through the supplementation of different doses of dietary VD₃ (0, 200, 400, 800 and 1600 μg VD₃/kg diet). According to our results, the optimal VD₃ level in the feed for turbot growth was estimated to be around 400 IU/kg, whereas VD₃ deficiency or overdose in diets induced the intestinal inflammation, lowered the diversity of gut microbiota and impaired the host resistance to bacterial infection in turbot. Moreover, the level of 1α,25(OH)₂D₃, the active metabolite of VD₃, reached a peak value in the turbot serum in the 400 μg group, although the concentrations of Ca and phosphate in the turbot were stable in all groups. Finally, the deficiency of dietary VD₃ disturbed the nutritional metabolism in turbot, especially the metabolism of lipids and glucose. In conclusion, this study evaluated the optimal dose of dietary VD₃ for turbot and provided the evidence that VD has a significant impact on intestinal health, host immunity and nutritional metabolism in fish, which deepened our understanding on the physiological functions and metabolism of VD₃ in fish.

Keywords: Infection; Inflammation; Metabolism; Microbiota; Vitamin D3.