Effects of Dietary Ferroporphyrin Supplementation on Growth Performance, Antioxidant Capacity, Immune Response, and Oxygen-Carrying Capacity in Gibel Carp (Carassius auratus gibelio)

An eight-week experiment was conducted to study the effects of dietary ferroporphyrin (FPR) supplementation on growth performance, antioxidant capacity, immune response, and oxygen-carrying capacity in gibel carp. The results demonstrated that the addition of FPR increased the moisture content of the whole fish body. Supplementation with 0.01% FPR significantly increased the plasma albumin (ALB), total protein (TP), and total cholesterol (TC) contents. The addition of 0.03% and 0.04% FPR significantly increased alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels, respectively, while the glucose (GLU), TC, and total triglyceride (TG) levels showed opposite trends. In terms of antioxidant capacity, the 0.03% and 0.04% dietary FPR supplementation increased malondialdehyde (MDA) levels. The activity of glutathione peroxidase (GPx) exhibited an opposite trend to MDA levels. The supplementation of 0.03% of FPR resulted in a notable reduction in mRNA expression levels of <i>nrf2</i>, <i>keap1</i>, <i>cat</i>, and <i>gpx.</i> Regarding immunity, 0.01% FPR supplementation down-regulated the expression levels of <i>il-1β</i> mRNA, while 0.02% FPR down-regulated <i>il-6</i> and <i>nf-κb</i> expression levels. Furthermore, 0.02% FPR supplementation significantly up-regulated the <i>il-10</i> mRNA expression levels. In terms of oxygen-carrying capacity, high levels of FPR (0.03% and 0.04%) were found to influence the <i>epo</i> and <i>vegf</i> mRNA expression. In conclusion, the incorporation of dietary 0.01-0.02% FPR improved the immune system of gibel carp without affecting their antioxidant and oxygen-carrying capacity. However, supplementation with higher levels of FPR (0.03-0.04%) led to decreased antioxidant and oxygen-carrying capacity.