A Study on the Function of Arginine in the Growth, Immunity, Antioxidant Activity, and Oxygen Carrying-Capacity of Juvenile Gibel Carp (Carassius auratus gibelio)

An eight-week trial was designed to study the effects of arginine (Arg) supplemented diets on the growth, immunity, antioxidant activity, and oxygen-carrying capacity of juvenile Gibel carp (<i>Carassius auratus gibelio</i>). A total of 300 fish (27.53 ± 0.03 g) were randomized into 15 equal groups and fed on diets with graded Arg levels: 0 (control), 0.2%, 0.4%, 0.6%, and 0.8% (<i>w</i>/<i>w</i>). The results showed that final body weight (FBW), weight gain rate (WGR), and specific growth rate (SGR) all increased and then declined with increasing levels of Arg supplementation, while feed conversion ratio (FCR) showed the opposite trend. In addition, the fish's whole-body crude protein and ash content had no remarkable difference at different levels of Arg addition (<i>p</i> > 0.05). Supplementation with 0.6% and 0.8% Arg significantly increased plasma alanine transaminase (ALT) activity (<i>p</i> < 0.05). The malondialdehyde (MDA) levels and superoxide dismutase (SOD) activities of the liver were not significantly different between the different levels of Arg supplementation (<i>p</i> > 0.05), while catalase (CAT) activity was significantly increased with 0.4% Arg supplementation levels (<i>p</i> < 0.05). The 0.8% Arg supplementation greatly increased the expression of hepatic-related genes to the Nrf2 signaling pathway, including <i>sod</i> and <i>gpx</i> (<i>p</i> < 0.05). However, the 0.8% Arg supplementation did not significantly increase the relative expression of genes related to the NF-κB signaling pathway, including <i>il-1β</i>, <i>il-8</i>, and <i>tnf-α</i> (<i>p</i> > 0.05). Similarly, the relative expression of hif-1 signaling pathway-related genes at 0.8% Arg supplementation was significantly elevated, including <i>hif-1α</i>, <i>epo</i>, and <i>vegf</i> (<i>p</i> < 0.05). Hence, Arg supplementation could promote growth and improve immune, antioxidant, and oxygen-carrying capacity in juvenile Gibel carp.