Effects of dietary supplementation of ferulic acid on growth performance, antioxidant ability, non-specific immunity, hepatic morphology and genes expression related to growth and immunity in juvenile hybrid grouper (Epinephelus fuscoguttatus♀ × Epinephelus polyphekadion♂)

Abstract

The current study was conducted to investigate the influences of ferulic acid (FA) as a dietary addition on growth performance, serum biochemical indices, liver morphology, antioxidant capacity, non-specific immunity, and expression of genes related to growth, immunity, apoptosis, and antioxidation in juvenile hybrid grouper (Epinephelus fuscoguttatus♀ × Epinephelus polyphekadion♂). Seven experimental diets added with 0 (Diet1), 40 (Diet2), 80 (Diet3), 160 (Diet4), 320 (Diet5), 640 (Diet6), and 1280 (Diet7) mg/kg FA, were formulated and fed to triplicate groups of 30 fish (9.51 ± 0.01 g) respectively for 10 weeks. The results exhibited that fish fed the diets with FA supplementation of 80 mg/kg presented the best growth performance and feed utilization, whereas the inclusion of 1280 mg/kg FA was the worst respect to Diet1 (control) (P < 0.05). The levels of serum low-density lipoprotein cholesterol, alanine aminotransferase, aspartate aminotransferase, total cholesterol, triglycerides, and alkaline phosphatase were significantly decreased, and high-density lipoprotein cholesterol level was increased following the FA-containing (80–160 mg/kg) diets (P < 0.05). Meanwhile, dietary 80–160 mg/kg FA administration provided an increase in the contents of complement 3, immunoglobulin M, and lysozyme (P < 0.05). The antioxidant-related parameters of superoxide dismutase, catalase, glutathione peroxidase, and total antioxidant capacity were outstandingly elevated, while malondialdehyde content was significantly reduced in 80–160 mg/kg FA treatment (P < 0.05). Additionally, dietary FA intake of 40–320 mg/kg could ameliorate hepatic morphology. Regarding genes expression, the transcriptional levels of immune-related genes (IL-1β, IL-8, TNF-α, IFN-γ) were considerably upregulated in the liver, head kidney, and spleen of fish fed the diets added with 80–160 mg/kg FA, which also significantly enhanced the expression of hepatic genes related to growth and antioxidation (GH, IGF-1, GHR1, GHR2, Nrf2, Cu/ZnSOD, and MnSOD). In contrast, the genes expression of apoptosis (Caspase-3 and p53) and keap1b were downregulated (P < 0.05). To sum up, dietary supplementation of FA at the optimal dosage (80 mg/kg) could enhance growth, antioxidant status, and immunity, as well as ameliorate liver morphology and health of fish. Interestingly, the high dosage (over 640 mg/kg) of FA had adverse effects on hybrid grouper, particularly for growth performance.