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In the present study, we aimed to evaluate the effects of dietary thymol on growth, antioxidant status, liver health, immune response and disease resistance of snakehead fish (Channa argus) (initial weight, 11.86 ± 0.15 g). The fish were fed for 56 days with a basal diet supplemented with thymol at 0, 150, 300, 450, 600 and 750 mg/kg, leading to six experimental diets. The final body weight (FBW), weight gain (WG), protein efficiency ratio (PER) and specific growth rate (SGR) were increased as dietary thymol level increased, arriving a summit value at 450 mg/kg dietary thymol level, and then, values of these indices started to decrease when dietary thymol level further rose, and feed conversion ratio (FCR) is the opposite state. Our results showed a significant increase (p <.05) in the superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH‐Px) activities in liver, spleen, head kidney and intestine with diets supplemented with 300 and 450 mg/kg thymol compared to the control and significantly decrease (p <.05) in the malondialdehyde (MDA) activity. Results showed that dietary supplementation with 300 and 450 mg/kg thymol significantly increased (p <.05) the serum acid phosphatase (ACP), alkaline phosphatase (AKP), lysozyme (LZM) activities and immunoglobulin M (IgM), complement 3 (C3), complement 4 (C4) concentrations of C. argus compared to the control, and decreased (p <.05) the serum glutamic‐pyruvic transaminase (ALT) and glutamic‐oxaloacetic transaminase (AST) activities. Moreover, the expression of HSP70, TNF‐α, IL‐1β and IL‐8 were down‐regulated in liver, head kidney and intestine by dietary supplementation with 300 and 450 mg/kg thymol, and the expression of IL‐10 and TGF‐β was up‐regulated. After challenge with Aeromonas veronii, survival rates in all thymol treatment groups were significantly increased (p <.05). Consequently, our results indicate that adequate dietary supplementation thymol can effectively enhance the growth, antioxidant status, immune response and disease resistance of C. argus, and the optimum dietary thymol requirement for maximum WG of C. argus was estimated to be 356 mg/kg. [ABSTRACT FROM AUTHOR]

The present study investigated the effects of dietary astaxanthin on the growth, blood biochemical, antioxidant, immune and inflammatory response in lipopolysaccharide‐challenged Channa argus. A total of 0, 50, 100 and 200 mg/kg of astaxanthin were added to the basal die for 56 days. After the feeding experiment, each group was subjected to a lipopolysaccharide challenge (except for the Control group). The results showed that adding astaxanthin to the diet can significantly increase the weight gain and specific growth rate and decrease the feed conversion ratio of C. argus; the highest weight gain, specific growth rate and minimum feed conversion ratio occurred in the 100 mg/kg group. Furthermore, dietary astaxanthin supplementation can alleviate the negative effects of lipopolysaccharides by increasing the levels of alkaline phosphatase, lysozyme, complement 3, complement 4, total serum protein, albumin, globulin, superoxide dismutase, catalase and glutathione peroxidase and decrease the serum cortisol, aspartate aminotransferase, alanine aminotransferase, glutathione peroxidase, and malondialdehyde. Dietary astaxanthin supplementation also can decrease the relative expression of inflammatory genes (nuclear factor κB, interleukin‐1, interleukin‐8 and tumour necrosis factor‐α) in the liver, spleen, kidney and intestine. To summarise, dietary astaxanthin addition can improve the growth performance and attenuate the negative effects of lipopolysaccharide challenge in C. argus. The optimal amount of astaxanthin is 100 mg/kg. [ABSTRACT FROM AUTHOR]

The present study investigated the effects of dietary Astragalus Propinquus schischkin polysaccharides on growth, immune responses, antioxidants responses and inflammation-related genes expression in Channa argus. Channa argus were randomly divided into 5 groups and fed 5 levels diets of A. propinquus schischkin polysaccharides (0, 250, 500, 1000 and 2000 mg/kg) for 56 days. The results showed, dietary A. propinquus schischkin polysaccharides addition can increase the final body weight, weight gain and specific growth rate, decrease the feed conversion ratio of Channa argus. And dietary A. propinquus schischkin polysaccharides supplementation can increase the levels of serum superoxide dismutase, catalase, glutathione peroxidase, lysozyme, complement 3, complement 4, immunoglobulin M and alkaline phosphatase, decrease the levels of serum malondialdehyde, cortisol, aspartate aminotransferase and glutamic-pyruvic transaminase. Furthermore, dietary A. propinquus schischkin polysaccharides can decrease the gene expression levels of interleukin-1β, interleukin-, tumor necrosis factor-α and nuclear factor-κB, increase the gene expression levels of glucocorticoid receptor in liver, spleen, kidney, intestine. To sum up, dietary A. propinquus schischkin polysaccharides can accelerate growth, enhance immune responses and antioxidants responses, regulate inflammation-related genes expression in Channa argus and the optimum amount is 1000 mg/kg. [Display omitted] • Astragalus Propinquus Schischkin polysaccharides accelerated growth in Channa argus. • Astragalus Propinquus Schischkin polysaccharides improved antioxidant and immune response in Channa argus. • Astragalus Propinquus Schischkin polysaccharides regulated serum biochemistry in Channa argus. • Astragalus Propinquus Schischkin polysaccharides regulated inflammation-related gene expression in Channa argus. [ABSTRACT FROM AUTHOR]