Study on Schizochytrium sp. improving the growth performance and non-specific immunity of golden pompano (Trachinotus ovatus) while not affecting the antioxidant capacity

A feeding experiment was conducted to determine the effects of Schizochytrium sp. on growth performance, antioxidant capacity and non-specific immunity in golden pompano (Trachinotus ovatus).Two diets were formulated with or without Schizochytrium sp. supplemented (D1:0% and D2: 3%) to feed fish for 8 weeks. Results showed that growth performance, feed intake and survival rate increased significantly with Schizochytrium sp. supplemented (P 0.05). Feed coefficient rate (FCR) of golden pompano fed the diet supplemented with Schizochytrium sp. was significantly lower than that of fish fed the control diet (P 0.05). No significant differences were found in antioxidant capacity both in transcriptional level, including nclear factor erythroid-2-related factor-2 (Nrf2), Kelch-like-ECH-associated protein (keap1), catalase (CAT), glutathione peroxidase (GSH-PX) and heme oxygenase 1 (HO-1) and enzyme activity, such as total antioxidant capacity (T-AOC), malondialdehyde (MDA) and superoxide dismutase (SOD) (P 0.05). Gut amylase and lipase were significantly higher in dietary Schizochytrium sp. supplemented treatment than that in control group (P 0.05). The relative peroxisome proliferator-activated receptor-α (PPARα) expression level in liver was significantly higher in Schizochytrium sp supplemented treatment than that in control one (P 0.05). The mRNA expression of myeloid differentiation factor 88 (MyD88), IL-1R-associated kinases 4 (IRAK4), interferon regulating Factor 3 (IRF3), interferon regulating Factor 3(IRF7) and heat shock protein 70 (HSP70) were significantly lower in Schizochytrium sp. supplemented treatment than that in control one (P 0.05). In Schizochytrium sp. supplemented diet, golden pompano had significantly longer villi length than that in control diet (P 0.05); muscle thickness in Schizochytrium sp. supplemented diet was thicker than that in control one (P 0.05) and there were more goblet cells in Schizochytrium sp. treatment (P 0.05). After the rearing trial, an air exposure trial was conducted. Results showed that the air-exposure mortality (AEM) and mRNA expression level of Nrf2, keap1, CAT, GSH-PX and HO-1 showed no significant difference (P 0.05). These results indicated that dietary Schizochytrium sp. improved the growth performance and non-specific immunity of golden pompano while made no difference to antioxidant capacity.