Effects of dietary Sargassum horneri on growth performance, serum biochemical parameters, hepatic antioxidant status, and immune responses of juvenile black sea bream Acanthopagrus schlegelii

Abstract

The black sea bream, Acanthopagrus schlegelii, an important marine species of high economic value and excellent meat quality, has suffered great losses due to disease in high-density aquaculture. The seaweed, Sargassum horneri (SH), which has various biologically active substances beneficial human and animal health, may serve as an immunostimulant in the aquaculture industry. The present study aimed at evaluating the effects of dietary S. horneri on growth performance, serum biochemical parameters, hepatic antioxidant status, and immune responses of juvenile A. schlegelii. Four-hundred and eighty fingerlings with approximate mean body weight 5.6 ± 0.1 g were randomly distributed into four experimental groups in triplicates. Each group was stocked with 40 fish and fed isonitrogenous (42% crude protein) and isolipid (12% crude lipid) experimental diets containing either 0% SH (control), 3% SH, 6% SH, or 9% SH for 8 weeks. Compared with the control group, final body weight, weight gain rate, and specific growth rate were improved significantly with 6% SH supplemented group (P < 0.05). Serum total protein and globulin contents in the S. horneri supplemented groups were significantly higher than those of the control group (P < 0.05). However, the levels of total cholesterol and triglyceride decreased with increasing dietary S. horneri levels, particularly in the 9% group (P < 0.05). Serum lysozyme, acid phosphatase, alkaline phosphatase, complement 3, and complement 4 levels were significantly higher in the 6% SH group with relative to the control group (P < 0.05). Apart from a significant decrease in malondialdehyde, the total antioxidant capacity, superoxide dismutase, and catalase activities in the liver of the S. horneri supplemented groups were significantly higher than those of control group (P < 0.05). The mRNA expression levels of interleukin-1β, interleukin-8, and tumor necrosis factor in the liver of fish significantly increased with S. horneri diets compared with control (P < 0.05), except for interleukin-8 in the 3% SH group. In conclusion, these results indicated that dietary S. horneri supplementation could promote growth performance, improve hepatic antioxidant status, and enhance immune ability of A. schlegelii, with an optimum supplemental level of 6% recommended in this study.