Modulation of digestive enzyme activities during ontogeny of Labeo rohita larvae fed ascorbic acid enriched zooplankton

Effects of dietary sodium butyrate on growth, digestive enzymes, body composition and nutrient retention-related gene expression of juvenile yellow catfish (Pelteobagrus fulvidraco)

An 8-week feeding trial was conducted to evaluate the effects of sodium butyrate (SB) on growth, digestive enzymes, body composition and nutrient retention-related gene expression of juvenile yellow catfish (Pelteobagrus fulvidraco). Five isonitrogenous and isolipidic diets (420 g/kg protein and 90 g/kg lipid) were formulated to contain 0 (control), 250, 500, 1,000 or 2,000 mg/kg SB. Triplicate groups of 40 fish (BW = 1.26 ± 0.01 g) per tank (300-L cylindrical fiberglass tanks) for each diet were fed to apparent satiation twice daily. Stomach, hepatopancreas and intestine samples were obtained for digestive enzymes activities analyses. A real-time quantitative PCR analysis was performed to determine the relative expression of target of rapamycin (TOR) and lipoprotein lipase (LPL) in the hepatopancreas and intestine. Fish fed the diets supplemented with SB at 500 and 1,000 mg/kg showed significantly higher specific growth rate and significantly lower feed conversion ratio compared to the control (P < 0.05). Dietary SB inclusion did not alter activities of intestinal amylase, creatine kinase and sodium–potassium adenosine triphosphatase (Na⁺/K⁺-ATPase), but increased activities of hepatic trypsin, stomachic lipase, intestinal lipase, alkaline phosphatase and γ-glutamyl transpeptidase for fish fed 1,000 mg/kg SB compared to the control (P < 0.05). Intestine length index, intestine somatic index, fold height and muscular thickness of distal intestine were significantly higher in 1,000 mg/kg SB groups compared to the control (P < 0.05). Significantly higher levels of whole-body crude protein, ash, calcium, phosphorus, nutrition retention and relative mRNA of intestinal TOR were observed in 1,000 mg/kg SB group (P < 0.05). Whole-body lipid content and hepatopancreas LPL mRNA expression in 2,000 mg/kg SB group were significantly higher than the control (P < 0.05). Relative mRNA levels of intestinal LPL and hepatopancreas TOR were significantly higher in the 500 mg/kg SB group compared to those in other groups (P < 0.05). The increased growth performance, digestive enzymes and nutrient retention in fish fed the diets supplemented with SB at 500 and 1,000 mg/kg suggests that SB can be a desirable growth promoter as an antibiotic alternative in diets.

Cinnamaldehyde improves the growth performance and digestion and absorption capacity in grass carp (Ctenopharyngodon idella)

The present study evaluated the effect of cinnamaldehyde (CIN) on the growth performance and digestion and absorption capacity of grass carp (Ctenopharyngodon idella). Fish were fed five diets including graded levels of CIN for 60 days. The results indicated that (1) appropriate CIN supplementation increased the growth performance and promoted the intestine growth of grass carp; (2) dietary appropriate CIN supplementation increased the digestion and absorption capacity by increasing the activities of intestinal and hepatopancreas digestive enzymes (lipase, chymotrypsin, trypsin, and amylase) and intestinal brush border enzymes (creatine kinase (CK), Na⁺/K⁺-ATPase, γ-glutamyl transpeptidase (γ-GT), and alkaline phosphatase (AKP)); (3) dietary CIN increased the absorption capacity which may be associated with the upregulated messenger RNA (mRNA) abundances of their amino acid transporters (AATs) in the intestine, which might be associated with activating the target of rapamycin (TOR) signaling pathway. The best CIN supplementation in the diets of grass carp was estimated to be 76.40 mg kg^-1 diet based on the best percent weight gain (PWG). In general, CIN increased the digestion and absorption capacity of grass carp and raised the mRNA abundances of AATs which may be partly related to activation of the TOR signaling pathway.

Effect of interactions between various humic acid fractions and iron nanoparticles on the toxicity to white rot fungus

Humic acid plays an important role in controlling the toxicity of nanoparticles to organisms. However, little is known about the influence of different fractions of dissolved humic acid (DHA) from soil on the toxicity of nanoparticles to organisms. The concentration of γ-Fe₂O₃ and the exposure time affected the malondialdehyde (MDA) content, reactive oxygen species (ROS) production and lactate dehydrogenase (LDH) activity in P. chrysosporium cells and were inversely proportional to the relative activities of the cells. P. chrysosporium was exposed to γ-Fe₂O₃ and DHA₁ for 3 h, 6 h and 12 h. Catalase (CAT) and peroxidase (POD) activities were generally higher than control. Particularly, under the influence of 50 mg/L DHA₁ and different concentrations of γ-Fe₂O₃ (10 and 50 mg/L), the CAT and POD activities were higher than those of cells exposed to γ-Fe₂O₃ alone. Conversely, both activities of P. chrysosporium exposed to DHA₄ combined with γ-Fe₂O₃ for 12 h were lower than those of cells exposed to γ-Fe₂O₃ alone and gradually decreased with increasing DHA₄ concentration (0, 10 and 50 mg/L). The μ-XAFS normalized spectrum indicated that Fe³⁺ entering the cells tended to transform into Fe²⁺ as the stress time prolonged. TEM analysis confirmed the toxicity of high concentrations of γ-Fe₂O₃ to P. chrysosporium. The comet assay showed that DHA₄ in soil enhanced the toxicity of γ-Fe₂O₃ to P. chrysosporium more than DHA₁ did. Namely, compared to DHA₁, DHA₄ made it easier for nano-Fe₂O₃ to enter P. chrysosporium cells, causing more toxicity of γ-Fe₂O₃ to P. chrysosporium.

Antioxidant status of serum, muscle, intestine and hepatopancreas for fish fed graded levels of biotin

Lipid peroxidation, protein oxidation and antioxidant activities of muscle, intestine, hepatopancreas and serum in juvenile Jian carp (Cyprinus carpio var. Jian) were investigated after feeding graded levels of biotin (0.010, 0.028, 0.054, 0.151, 0.330, 1.540 and 2.680 mg kg(-1) diet) for 63 days. Both malondialdehyde and protein carbonyl content in all studied tissues and serum were the lowest in fish fed diets containing 0.151-0.330 mg biotin kg(-1) diet and then increased in fish fed the diet with 2.680 mg biotin kg(-1) diet (P < 0.05). Similarly, glutamate-oxaloacetate transaminase and glutamate-pyruvate transaminase activities in serum significantly decreased with biotin levels up to 0.151 mg kg(-1) diet (P < 0.05). Conversely, capacities of anti-hydroxyl radical (AHR) and anti-superoxide anion (ASA) in the detected tissues and serum significantly improved with biotin levels up to 0.054-1.540 mg kg(-1) diet and then decreased in 2.680 mg biotin kg(-1) diet group for muscle and intestinal AHR as well as hepatopancreas ASA (P < 0.05). Activities of superoxide dismutase in all studied tissues and serum significantly elevated with biotin levels up to 0.330 mg kg(-1) diet and then decreased when fish fed the diet with 2.680 mg biotin kg(-1) diet, except intestine (P < 0.05). Meanwhile, activities of catalase, glutathione peroxidase, glutathione-S-transferase and glutathione reductase and total thiol content in all studied tissues and serum showed the upward trend with biotin supplementations (P < 0.05). These results indicated that biotin improved antioxidant status and depressed lipid peroxidation and protein oxidation in all studied tissues and serum.

Effect of dietary arginine on growth, intestinal enzyme activities and gene expression in muscle, hepatopancreas and intestine of juvenile Jian carp (Cyprinus carpio var. Jian)

The present study was conducted to test the hypothesis that dietary arginine promotes digestion and absorption capacity, and, thus, enhances fish growth. This improvement might be related to the target of rapamycin (TOR) and eIF4E-binding protein (4E-BP). A total of 1200 juvenile Jian carp, Cyprinus carpio var. Jian, with an average initial weight of 6.33 (SE 0.03) g, were fed with diets containing graded concentrations of arginine, namely, 9.8 (control), 12.7, 16.1, 18.5, 21.9 and 24.5 g arginine/kg diet for 9 weeks. An real-time quantitative PCR analysis was performed to determine the relative expression of TOR and 4E-BP in fish muscle, hepatopancreas and intestine. Dietary arginine increased (P < 0.05): (1) glutamate-oxaloacetate transaminase and glutamate-pyruvate transaminase activities in muscle and hepatopancreas; (2) intestine and hepatopancreas protein content, folds height, and trypsin, chymotrypsin, lipase, Na⁺/K⁺-ATPase, alkaline phosphatase, γ-glutamyl transpeptidase and creatine kinase activities in intestine; (3) Lactobacillus counts; (4) relative expression of TOR in the muscle, hepatopancreas and distal intestine (DI); (5) relative expression of 4E-BP in proximal intestine (PI) and mid-intestine (MI), as compared with the control group. In contrast, dietary arginine reduced (P < 0.05): (1) plasma ammonia content; (2) Aeromonas hydrophila and Escherichia coli counts; (3) relative expression of TOR in PI and MI; (4) relative expression of 4E-BP in the muscle, hepatopancreas and DI. The arginine requirement estimated by specific growth rate using quadratic regression analysis was found to be 18.0 g/kg diet. These results indicate that arginine improved fish growth, digestive and absorptive ability and regulated the expression of TOR and 4E-BP genes.