Vitamin D3 Supplementation on Antioxidant Capacity and Ferroptosis in Juvenile Gibel Carp (Carassius auratus gibelio var. CAS V) at Different Stocking Densities

• • Dietary VD3 at 5000 IU/kg significantly reduced hepatic LPO and Fe2+ contents (P=0.0448 and P=0.0054, respectively) under high-density stress, mitigating ferroptosis markers. • • High-density rearing (210 fish/tank) significantly decreased hepatic GPT activity (P<0.0001) and increased GPx4 activity (P=0.0446) and GSH content (P=0.0002), indicating compensatory antioxidant responses. • • VD3 supplementation significantly upregulated antioxidant genes nrf2 (P=0.0029), gpx4a (P<0.0001), and prdx6 (P=0.0003), and downregulated pro-ferroptosis gene acsl4a (P<0.0001 for interaction), aligning with transcriptomic trends. • • Transcriptomic analysis revealed enrichment in ferroptosis, cysteine and methionine metabolism, and fatty acid biosynthesis pathways, with RNA-seq mapping rates exceeding 89.8% across all samples, ensuring data reliability.