Dietary Vitamin D3 Requirement and Its Effects on Growth and Bone Mineralization in Large Yellow Croaker (Larimichthys crocea)

Vitamin D3 (VD3) plays a critical role in bone mineralization and growth in fish, yet its dietary requirement for large yellow croaker (Larimichthys crocea) remains unclear. This study aimed to determine the optimal VD3 level for growth performance and bone health in large yellow croaker. A 9-week feeding trial was conducted with juvenile large yellow croaker (6.16 ± 0.19 g) using six isonitrogenous and isoenergetic diets containing graded VD3 levels (measured: 32.7, 216.8, 392.5, 773.2, 1524.5, and 3071.6 IU kg−1). Growth indices (weight gain, specific growth rate, feed efficiency ratio, protein efficiency ratio) increased significantly (p < 0.05) when dietary VD3 rose from 32.7 to 392.5 IU kg−1, then plateaued. VD3 supplementation significantly affected hepatic VD3 content, whole-body ash, calcium, and phosphorus levels, and mineralization of vertebrae, opercula, and scales, as well as serum alkaline phosphatase, hydroxyproline, calcium, and inorganic phosphorus (p < 0.05). Based on a broken-line model using weight gain, the dietary VD3 requirement was estimated at 426.5 IU kg−1; using a quadratic model with hepatic VD3 content, the estimate was 2388.9 IU kg−1. Overall, appropriate dietary VD3 supplementation is essential to support optimal growth and bone mineralization of juvenile large yellow croaker. This finding provides a scientific basis for dietary VD3 recommendations to optimize growth and bone health in large yellow croaker, contributing to improved aquaculture productivity.