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The effects of selenium supplementation in Tachysurus fulvidraco (T. fulvidraco) on low-temperature stress are not known. In this study, 280 healthy T. fulvidraco were divided into two groups, the G0 group (a control group) and the T0 group (a selenium treatment group on a 0.22 mg/kg diet), for a 6-week feeding time. Then, low-temperature stress (water temperature dropped from 26 to 13 °C, with a rate of 1 °C/h) was administered after that. The feeding results showed that selenium increased the percent weight gain (PWG), specific growth rate (SGR), and survival rate (SR) of T. fulvidraco and decreased the feed conversion rate (FCR), but these differences were not significant (p > 0.05). Under low temperatures, selenium still has no significant effects on antioxidant indexes such as glutathione peroxidase (GSH-Px) activity, superoxide dismutase (SOD) activity, and malondialdehyde (MDA) content in serum (p > 0.05). However, metabolomic analysis revealed that selenium caused changes in lipids and lipid-like molles, organic acids and their derivatives, and fatty acyls. Choline, linoleic acid, and glycerophospholipid metabolism pathways; d-arginine and d-ornithine metabolism; valine, leucine, and isoleucine degradation; and biosynthesis pathways, as well as pyrimidine metabolism pathways, were activated to produce these metabolites to combat against this stress. In addition, selenium increased the diversity of intestinal microbes in T. fulvidraco and decreased the relative abundance of Plesiomonas. However, the combined analysis showed the intestinal microbe changes did not affect metabolite production. In summary, selenium activated lipid, carbohydrate, and amino acid metabolism for energy substance provision, reduced the oxidation and production of other harmful substances, and increased the intestinal microbe diversity of T. fulvidraco to improve resistance to low-temperature stress. [ABSTRACT FROM AUTHOR]

The effects of vitamin B1 on growth, blood metabolites, body composition, intestinal enzyme activities and morphometric parameters were evaluated by a 63‐day feeding trial in Pelteobagrus fulvidraco fed diets containing vitamin B1 with 4.29, 6.02, 7.86, 11.94 and 19.05 mg/kg, respectively. Results showed that 7.86 mg/kg vitamin B1 resulted in significantly higher weight gain (WG), specific growth rate (SGR) and protein efficiency ratio (PER) (p <.05). Serum triglyceride, cholesterol and whole‐body lipid were observed in 11.94 mg/kg vitamin B1 group significantly higher than those in 4.29 mg/kg group, accompanied by the lower serum glucose content in the same group (p <.05). Significantly higher values of whole‐body protein, serum total protein, relative intestinal length, fold height, intestinal trypsin, amylase, alkaline phosphatase, Na+/K+‐ATPase, γ‐glutamyl transpeptidase, creatine kinase, muscular layer thickness and intestosomatic index were observed in 7.86 mg/kg vitamin B1 group compared with those in 4.29 mg/kg group (p <.05). These results suggested that diets supplemented with vitamin B1 improved growth performance, feed utilization, intestinal digestive and absorption capacity of juvenile yellow catfish. The optimal dietary vitamin B1 requirements estimated using a two‐slope broken‐line model based on WG and PER of yellow catfish were 7.42 and 6.01 mg/kg, respectively. [ABSTRACT FROM AUTHOR]

The effects of N‐carbamylglutamate (NCG) on growth, intestinal enzyme activities, immunological and antioxidant parameters were evaluated by a 56‐d feeding trial in Pelteobagrus fulvidraco fed diets containing NCG with 0, 250, 500, 1,000 or 2,000 mg/kg, respectively. The results showed that 250 mg/kg of NCG resulted in significantly higher weight gain, intestine fold height, intestine lipase, serum lysozyme, glutathione peroxidase and total antioxidant capacity than control (p < 0.05). However, higher intestine trypsin, arginase, arginine decarboxylase, ornithine decarboxylase, diamine oxidase activities and serum nitric oxide content were observed in 500 mg/kg NCG group compared to control or 2,000 mg/kg (p < 0.05). The survival rate, intestine muscular layer thickness, serum lysozyme and superoxide dismutase activities in 2,000 mg/kg NCG group were significantly lower than those in control and 250 mg/kg group, accompanied by the higher feed conversion ratio in the same group (p < 0.05). Together, dietary NCG level at 250 or 500 mg/kg improved growth, intestinal enzyme activities, immunological and antioxidant abilities, while high NCG level of 2,000 mg/kg had a negative effect. Quadratic regression analysis on weigh growth, diamine oxidase and lysozyme activities indicated that the recommended optimum dietary NCG level was 213.48–314.50 mg/kg of the dry diet. [ABSTRACT FROM AUTHOR]

The effects of nucleotides on growth, and physiological and antioxidant parameters were evaluated by feeding Pelteobagrus fulvidraco diets supplemented with 0, 0.2, 0.4, 0.6, 1.0 or 1.5 g kg−1 of nucleotides respectively. All nucleotide groups showed higher specific growth rate, feed efficiency, protein efficiency ratio, whole-body lipid content and serum cholesterol concentrations than the control group, but the significant difference was seen only between fish from the 1.5 g kg−1 nucleotide group and fish from the control group. Whole-body ash content in fish from the 0.6 g kg−1 nucleotide group, and liver superoxide dismutase and catalase in fish from the 0.4 g kg−1 nucleotide group were significantly higher than those in fish from the control group. Respiratory burst activity was significantly higher in fish from the 0.6, 1.0 and 1.5 g kg−1 nucleotide groups than in fish from the control. This finding was accompanied by lower liver concentrations of thiobarbituric acid-reacting substances in fish from the same groups compared to those from the control group. The results indicate that dietary nucleotides could improve growth and antioxidant responses in juvenile yellow catfish. [ABSTRACT FROM AUTHOR]

The effects of dietary sodium butyrate (SB) on serum metabolic parameters, intestinal antioxidant status, immune response and resistance to ammonia stress in Pelteobagrus fulvidraco were investigated. The fish were fed with diets containing 0, 250, 500, 1000 or 2000 mg/kg SB for 56 days followed by a 72-h ammonia challenge (2.65 mg/L unionized ammonia-N). The results showed that 500 and 1000 mg/kg SB groups showed significantly higher weight gain rate than control. Dietary SB significantly decreased cumulative mortality after 72 h ammonia nitrogen stress (P < 0.05). Ammonia challenge significantly increased serum total protein, cortisol, glucose, BUN, ALT and AST and decreased serum triglyceride. SB, especially at 1000 mg/kg, significantly decreased serum cortisol, glucose and BUN, ALT, AST and increased serum total protein lactate and triglyceride. Ammonia had no effects on ALP activity but SB at 1000 mg/kg significantly increased the enzyme activity. Fish fed the diet containing 500 or 1000 mg/kg SB supplementation had higher activities of intestinal SOD, CAT and GPx than that fed the control diet (P < 0.05). The highest MDA was occurred at the fish fed the control diet among all groups (P < 0.05). Compared with the control group, the relative expressions of cu/Zn-SOD, CAT and GPx were significantly increased and the relative expressions of IL-1, IL-8, TNF-α, p53 and Bax were significantly decreased in fish fed with 1000 mg/kg SB group after ammonia stress (P < 0.05). Dietary SB improved the resistance to ammonia stress in juvenile yellow catfish (Pelteobagrus fulvidraco) though influencing serum metabolite, intestinal antioxidant status and immune response • Sodium butyrate (SB) supplement significantly reduced the mortality caused by ammonia stress. • SB can modulate serum metabolic parameters under ammonia stress. • SB supplement significantly improved the antioxidant status and immune response of Pelteobagrus fulvidraco. [ABSTRACT FROM AUTHOR]