Effect of Dietary Marine Red Yeast Rhodotorula mucilaginosa on the Growth Performance, and also Non-Specific Immune Responses of Juvenile Golden Pompano Trachinotus Ovatus when Challenged with Vibrio Harveyi

The present study was conducted to investigate the effects of dietary marine red yeast Rhodotorula mucilaginosa supplementation on the growth performance, non-specific immune responses, and resistance to the pathogen Vibrio harveyi in Golden Pompano Trachinotus ovatus. A basal diet was supplemented with R. mucilaginosa at 0‰ (control), 1‰, 2‰, 3‰, 4‰, and 5‰ for 8 weeks. After the 8-week feeding trial, weight gain (WG) and specific growth rate (SGR) were significantly affected by the R. mucilaginosa levels, with the highest WG and SGR occurring at the 1‰ R. mucilaginosa level (P<0.05). Compared to the control, the 4 and 5‰ R. mucilaginosa groups had significantly increased lysozyme (LYZ) and alkaline phosphatase (AKP) activity, but a decrease in nitric oxide synthase (NOS) was noted (P<0.05). Compared to the control, the 2, 3 and 4‰ R. mucilaginosa groups had significantly increased hepatic superoxide dismutase (SOD) activity (P<0.05), while hepatic malondialdehyde (MDA) content decreased significantly (P<0.05). After challenge with V. harveyi, the group supplemented with 1‰ R. mucilaginosa had 100% survival rate. In addition, compared to the control group prior to challenge, the serum C3 level significantly increased in the group supplemented with 2‰ R. Mucilaginosa (P < 0.05). Compared to the control 12 h and 48h after challenge, serum C4 levels in the 4‰ R. Mucilaginosa group increased significantly (P<0.05). Our results suggest that ingestion of a basal diet supplemented with 1-3‰ R. mucilaginosa in T. ovatus could enhance resistance against the pathogen Vibrio harveyi.