Intestinal Enzyme Activities Research Articles

Effects of cannabidiol on growth performance, appetite, antioxidant capacity and liver inflammatory gene expression of juvenile large yellow croaker (Larmichthys crocea) fed diets with high soybean oil level

This study evaluated the effects of cannabidiol (CBD) on growth performance, appetite, antioxidant capacity and liver inflammatory gene expression in juvenile large yellow croaker (Larmichthys crocea) fed diets with fish oil replaced by soybean oil. Six iso‑nitrogenous and isolipidic diets were formulated with fish oil (FO, the standard diet compared with the control only), soybean oil (SO, the control) and SO supplemented with 25, 50, 100 and 250 mg/kg CBD. After 9-week feeding, with the increase of CBD supplementation in SO diet, the growth performance (final body weight, specific growth rate and feed intake) and the intestinal digestive enzyme activities (amylase, lipase and trypsin) showed a significantly quadratic trend of variation and the maximum were observed in the fish fed SO diets with 100 mg/kg CBD. Correlation analysis showed that 100 mg/kg CBD supplemented in the SO diet could promote appetite of fish by inhibiting the mRNA expression of pro-opiomelanocortin in hypothalamus. The activities of aspartate transaminase and alanine transaminase and total protein level in the serum of fish showed a significantly quadratic trend with the supplementation of CBD increasing in SO diets, and the lower were observed in fish fed SO diets with CBD. Compared with the control, 25, 50, 100 and 250 mg/kg CBD supplemented in SO diets increased peroxidase activity and total antioxidant capacity and decreased malondialdehyde content in the liver of fish, and the highest superoxide dismutase activity was observed in fish fed SO diets with 100 mg/kg CBD. Moreover, fish fed SO diets with 100 and 250 mg/kg CBD had lower mRNA expression of tumor necrosis factor α, interleukin-1β, interleukin-6 and cyclooxygenase-2 in liver of fish compared with the control. In conclusion, 100 mg/kg CBD supplemented in diets with high SO level improved the growth performance and appetite in large yellow croaker. Simultaneously, the supplementation of 100 and 250 mg/kg CBD could promote antioxidant capacity and inhibit the inflammatory gene expression in liver of large yellow croaker fed diets with the high SO level. The optimal supplementation of CBD in diets with high SO level is recommended at 100 mg/kg for large yellow croaker.

Dietary hydrolyzable tannins reduce growth performance and induce histological damage of Chinese seabass (Lateolabrax maculatus)

Chinese seabass (Lateolabrax maculatus) is a popular carnivorous fish with delicious taste. Although the feed value of condensed tannins has been well documented for L. maculatus, information about the effects of hydrolyzable tannins (HTs) on the growth and health of L. maculatus is limited. This study was conducted to assess the effects of dietary HTs on growth performance, body composition, intestinal digestive enzyme activities, serum metabolites, antioxidant and immune response, and intestine and liver morphology of L. maculatus. A total of 640 fish were randomly divided into four groups with four replicates per group and 40 fish per replicate. Four diets were prepared to contain 0 (G0), 1 (G1), 2 (G2), and 4 (G4) g/kg of HTs. Fish were fed to apparent satiation twice a day during the 56-day feeding trial. Results showed that the final body weight, weight gain rate, specific growth rate, and feed intake were linearly decreased (p< 0.001) as dietary HTs increased. All fish had similar (p > 0.05) whole body compositions. Fish fed G2 and G4 had lower (p< 0.05) intestinal trypsin and lipase activities than those fed G0 and G1, whereas G4 had higher (p< 0.05) aspartate aminotransferase and alanine aminotransferase activities than G0. Serum total antioxidant capacity and lysozyme were linearly decreased (p< 0.01), but the malondialdehyde concentration was linearly increased (p< 0.01) as dietary HTs increased. Intestinal villi in G2 and G4 showed increased deformation, and the vacuolation of liver cells began to appear in G1 and was aggravated as dietary HTs increased. This study showed that HTs should be used with caution due to their growth-inhibiting effect, and the dietary HT level for L. maculatus is recommended to be less than 1 g/kg.

Application of enzymatically treated Artemisia annua L. on adult grass carp (Ctenopharyngodon idella): Improved growth performance, intestinal antioxidant capacity and apical junctional complex

The present study evaluated the effects of enzymatically treated Artemisia annua L. (EA) on the growth performance, intestinal antioxidant capacity, and apical junctional complex (AJC) of adult grass carp. In this experiment, 375 healthy grass carp (initial body weight 673.96 ± 1.24 g) were selected and randomly divided into 5 treatments, and fish in each group were fed diets with different levels of EA (0, 400, 800, 1200, and 1600 mg/kg) 9 weeks. The results showed that compared with the control group (0 mg/kg EA diet), the EA supplementation in the diet increased the percentage of weight gain (PWG), specific growth rate (SGR), and feed intake (FI) (P < 0.05), indicating that dietary EA supplementation improved the growth performance of adult grass carp. The dietary EA supplementation also enhanced the digestion and absorption ability of adult grass carp, which might be reflected by improving the activities of hepatopancreas digestive enzymes (trypsin, chymotrypsin, lipase, and amylase) and intestinal brush border enzymes (alkaline phosphatase, Na+/K+-ATPase, and γ-glutamyl transpeptidase), but EA did not affect the creatine kinase enzyme activity. Meanwhile, we explored the effect of dietary EA addition on the structural integrity of the grass carp intestine. We observed that dietary EA supplementation improved the antioxidant capacity of the intestine which be reflected by increasing the activities levels of superoxide dismutase (SOD) and catalase (CAT), which might be related to the binding protein Keap1a (not Keap1b)/ NF-E2-related factor-2 (Nrf2) signaling pathway. In addition, dietary EA supplementation enhanced the integrity of AJC by increasing the mRNA levels of intestinal tight junction proteins (TJs) (except claudin 11, claudin 12, claudin 15a) and adhere junction proteins (AJs) (E-cadherin, α-catenin, β-catenin, nectin, and afadin), which might be related to the Rho family GTPases (RhoA)/ Rho-associated protein kinase (ROCK)/ myosin light chain kinase (MLCK) signaling pathway. Collectively, dietary EA supplementation improved growth performance, digestion and absorption ability, and intestinal structural integrity in grass carp, which were associated with the activation of related signaling pathways and regulatory factors. Finally, by the growth indicator percent weight gain (PWG) and intestinal oxidative damage index protein carbonyl (PC), the optimum amounts of EA supplementation of adult grass carp (673–1726 g) were assessed to be 808.09 and 730.38 mg/kg diet, respectively.

Effects of artificial diet breeding on intestinal microbial populations at the young stage of silkworm (Bombyx mori).

The silkworm (Bombyx mori) is an economically important insect and serves as a model organism for Lepidoptera. To investigate the effects of the intestinal microbial population on the growth and development of larvae fed an artificial diet (AD) during the young stages, we analyzed the characteristics of the intestinal microbial population using 16S rRNA gene sequencing technology. Our results revealed that the intestinal flora of the AD group tended to be simple by the 3rd-instar, which Lactobacillus accounting for 14.85% and leading to a decreased pH in the intestinal fluid. In contrast, the intestinal flora of silkworms in the mulberry leaf (ML) group showed continuous growth of diversity, with Proteobacteria accounting for 37.10%, Firmicutes accounting for 21.44%, and Actinobacteria accounting for 17.36%. Additionally, we detected the activity of intestinal digestive enzymes at different instars and found that the activity of digestive enzymes in the AD group increased by larval instar. Protease activity in the AD group was lower during the 1st- to 3rd-instars compared to the ML group, while α-amylase and lipase activities were significantly higher in the AD group during the 2nd- and 3rd-instar compared to the ML group. Furthermore, our experimental results indicated that changes in the intestinal population decreased the pH and affected the activity of proteases, which might contribute to the slower growth and development of larvae in the AD group. In summary, this study provides a reference for investigating the relationship between artificial diet and intestinal flora balance.

Effect of dietary bile acids supplementation on growth performance, feed utilization, intestinal digestive enzyme activity and fatty acid transporters gene expression in juvenile leopard coral grouper (Plectropomus leopardus)

This study aimed to evaluate the effects of dietary bile acids on growth performance, feed utilization, body composition, digestive enzyme activity, and related gene expression in juvenile leopard coral grouper (Plectropomus leopardus). Five diets with varying levels of dietary bile acids (0, 0.15, 0.3, 0.45 and 0.6%) were formulated and each diet was fed to triplicate groups of 15 fish (13.14 ± 0.14 g) for ten weeks. Results showed that the significant enhancement in weight gain (WG) and specific growth rate (SGR) was observed in fish fed 0.3% bile acids (P &amp;lt; 0.05). Additionally, feed conversion ratio (FCR) was significantly improved with bile acids inclusion (P &amp;lt; 0.05). Higher feed intake was also recorded in bile acids inclusion groups, and significantly up-regulated gene expression of hypothalamus neuropeptide Y (NPY) was found in 0.3% group compared with the control group (P &amp;lt; 0.05). Dietary bile acids (0.3%) significantly decreased lipid deposition in the whole-body (P &amp;lt; 0.05), and lower hepatosomatic index (HSI) and viscerosomatic index (VSI) were also found in this group. Moreover, intestinal trypsin and lipase activities were significantly increased in 0.3% group (P &amp;lt; 0.05) to promote feed digestion. In addition, the relative expression levels of intestinal fatty acid binding protein 2 (FABP2) significantly up-regulated with inclusion of dietary bile acids, suggesting an enhancement of fatty acid transport (P &amp;lt; 0.05). In contrast, cholesterol transport related genes NPC1 like intracellular cholesterol transporter 1 (NPC1L1) and CD36 were notably down-regulated as bile acids inclusion (P &amp;lt; 0.05). This study provides valuable information for the formulation of diets for juvenile coral trout and indicates that dietary bile acids could potentially be used to improve growth performance and feed utilization.

Encapsulation of SOD in chitosan-coated gel particles of alginate or mixture of alginate and shellac for targeted intestinal delivery

The chitosan-coated alginate gel particles (CS/SA) and chitosan-coated alginate-shellac gel particles (CS/SA/Lac) were constructed to serve as a potential oral delivery system to enhance the stability and activity of superoxide dismutase (SOD) in this study. The encapsulation efficiency (EE), enzyme activity retention ratio (ER), particle structure, and SOD release behavior, as well as the effect of shellac, were evaluated. The best formula is determined by the percentage of total effective activity (PTEA).The results showed that CS/SA prepared by 0.30‰ chitosan, 1.00% CaCl2, 2.00% sodium alginate (M/G = 1:1, Mw: 38,857 kDa), and gelation solution pH 5.50 had the best chitosan shell, the strongest gel structure and the maximum PTEA which was 10.75 ± 1.45%. Based on the optimal formula, addition of shellac that formed shellac-Ca2+ microspheres in the gel network was averse to SOD encapsulation, but it significantly improved the stability of SOD in gastric conditions. By adding 15.00% shellac, the PTEA reached 16.30 ± 1.64%. At optimal formulation, SOD encapsulated in CS/SA was completely released in the stimulated intestinal fluid and accumulative release enzyme activity (EA) was 966.62 ± 103.75 (U) after 6 h. However, the CS/SA/Lac with a low swelling ratio only released SOD in stimulated colonic fluid and the EA value reached 1692.28 ± 101.82 (U) after 1 h. These findings demonstrated that CS/SA and CS/SA/Lac were excellent candidates for SOD oral administration, which was useful in the food and biomedical industries for developing functional products containing SOD.

Effects of Replacement of Fish Meal with Poultry By-Product Meal (PBM) on Growth Performance, Digestive Enzyme, and Immunity of Giant River Prawn (Macrobrachium rosenbergii)

A 56-day feeding trial was performed to determine the effect of replacing fishmeal with 0, 25%, 50%, 75%, and 100% PBM (FM) on growth performance, digestive enzyme, and immunity of juvenile giant river prawn (Macrobrachium rosenbergii). Diets were fed in quadruplicate (50 prawns per replicate) to satiation (3–5% of their body weight). The finial weight, weight gain, and specific growth rate of prawns were significantly reduced P &lt; 0.05 when 100% PBM was substituted for fish meal, whereas the remaining test diets showed no variation compared to the control P &gt; 0.05 . There was no significant difference in survival rates. The moisture, crude protein, and crude fat of the prawn were unchanged P &gt; 0.05 . The SOD activity, MDA content, and AKP activity of hemolymph did not change significantly. However, the ACP activity of all replacement groups decreased significantly P &lt; 0.05 . The amylase enzyme activity in the intestine of prawn fed 25% of PBM increased significantly compared with the control group, while the trypsin and lipase activities were unchanged. This study showed that PBM up to 75% replacement group does not affect growth performance, and all replacement groups have no adverse effect on intestinal digestive enzyme activity and immunity in juvenile M. rosenbergii. Therefore, poultry by-product meal could replace fish meal by up to 75%.

DietaryPeriplaneta americana extract improved the growth performance, immune, and antioxidative status, and crowding stress responses in Nile tilapia

The objective of this study was to assess the beneficial effects of dietaryPeriplaneta americana extract (PAE) supplementation on growth performance, immune, and antioxidative status, liver health, and crowding stress responses in Nile tilapia (Oreochromis niloticus). The fish (initial weight 55.01±1.73 g) were fed with one of the four diets containing PAE (0, 1, 2 and 4%) for 60 days followed by a 3-h crowding stress trial. PAE enhanced the weight gain rate at concentrations of 2 and 4% and lowered the feed conversion rate at 4% (P&lt;0.05), which possibly due to the increased activities of intestinal protease and amylase (P&lt;0.05). Dietary PAE supplementation at 2 and 4% increased levels of total protein and albumin, while PAE at 4% increased complement C3 and C4 levels (P&lt;0.05). Dietary PAE supplementation also enhanced serum lysozyme activity at all concentrations tested (P&lt;0.05). Fish fed with 2 and 4% PAE exhibited lower activities of serum enzymes, including alkaline phosphatase, alanine aminotransferase, and aspartate aminotransferase (P&lt;0.05). Dietary PAE supplementation at 2 and 4% significantly decreased malondialdehyde and increased levels of superoxide dismutase, catalase and glutathione. In addition, PAE demonstrated hypolipidemic and hypocholesterolemic effects, as reflected by lower serum levels of total cholesterol, triglycerides, and higher density lipoprotein cholesterol in the 1-4% groups compared to the 0% group. Crowding stress affected serum cortisol and glucose levels in all treatments (P&lt;0.05), but PAE supplementation alleviated increase in the serum cortisol and glucose after stress trial (P&lt;0.05). In conclusion, PAE has the potential to enhance growth performance, improve the intestinal enzyme activities and immune and antioxidative status, alleviating the negative effects of crowding stress in Nile tilapia juveniles. The recommended dietary levels of PAE were 20-40 g/kg for Nile tilapia.

Effects of Starvation and Refeeding on Growth, Digestion, Nonspecific Immunity and Lipid-Metabolism-Related Genes in Onychostoma macrolepis.

The present research was conducted to assess the influences of starvation and refeeding on growth, nonspecific immunity and lipid metabolic adaptation in Onychostoma macrolepis. To date, there have been no similar reports in O. macrolepis. The fish were randomly assigned into two groups: control group (continuous feeding for six weeks) and starved-refed group (starvation for three weeks and then refeeding for three weeks). After three weeks of starvation, the results showed that the body weight (BW, 1.44 g), condition factor (CF, 1.17%), visceral index (VSI, 3.96%), hepatopancreas index (HSI, 0.93%) and intraperitoneal fat index (IPFI, 0.70%) of fish were significantly lower compared to the control group (BW, 5.72 g; CF, 1.85%; VSI, 6.35%; HSI, 2.04%; IPFI, 1.92%) (p < 0.05). After starvation, the serum triglyceride (TG, 0.83 mmol/L), total cholesterol (T-GHOL, 1.15 mmol/L), high-density lipoprotein (HDL, 1.13 mmol/L) and low-density lipoprotein (LDL, 0.46 mmol/L) concentrations were significantly lower than those in the control group (TG, 1.69 mmol/L; T-GHOL, 1.86 mmol/L; HDL, 1.62 mmol/L; LDL, 0.63 mmol/L) (p < 0.05). The activities of intestinal digestive enzymes (amylase, lipase and protease) in the starved-refed group were significantly lower than those in the control group after three weeks of starvation (p < 0.05). The highest activities of immune enzymes such as lysozyme (LZM), acid phosphate (ACP), alkaline phosphate (ALP), superoxide dismutase (SOD), glutathione peroxidase (GSH-PX) and catalase (CAT) in the hepatopancreas were presented in the starved-refed group at second week, and significantly higher than those in the control group (p < 0.05). Meanwhile, starvation significantly improved intestinal immune enzymes activities (p < 0.05). the lowest TG contents and the highest expression levels of lipolysis genes including hormone-sensitive lipase (HSL) and carnitine palmitoyl transferase 1 isoform A (CPT-1A) appeared in the hepatopancreas, muscle and intraperitoneal fat after starvation, indicating the mobilization of fat reserves in these tissues (p < 0.05). After refeeding, the recovery of TG content might be mediated by the upregulation of the expression levels of lipogenesis genes such as sterol regulatory element binding protein 1 (SREBP1) and fatty acid synthase (FAS). Understanding the duration of physiological and metabolic changes in O. macrolepis and their reversibility or irreversibility to supplementary feeding response could provide valuable reference for the adaptability of O. macrolepis in large-scale culturing, proliferation and release.

Bacillus subtilis and Pichia farinose mixture improves growth performance and nutrient absorption capacity in broiler chicks.

This study evaluated the effects of dietary supplementation of Bacillus subtilis and Pichia farinose mixture (BPM) on growth performance, apparent ileal digestibility, cecal bacteria counts, small intestinal morphology and digestive enzymes activities, and jejunal nutrient transporters gene expression in broiler chicks. A total of 768 one-day-old Ross 308 broiler chicks were randomly Q18 assigned into 3 groups based on the initial body weight (42.00 ± 0.08 g). The experimental periods were 35 days. There were 16 replicates per group and 16 birds per cage. Dietary treatments included a basal diet supplemented with 0, 0.1, or 0.2% BPM to form CON, BPM0.1 (consisting Bacillus subtilis with 1.0 × 107 viable spore and Pichia farinose with 1.0 × 107 viable spore per kg diet), and BPM0.2 (consisting Bacillus subtilis with 2.0 × 107 viable spore and Pichia farinose with 2.0 × 107 viable spore per kg diet) groups. Dietary supplementation of graded levels of BPM has positive effects on growth performance of broiler chicks, manifesting in the increase of body weight gain during days 1-35 as well as the decrease of feed conversion ratio during days 1-7, 21-35, and 1-35. Moreover, BPM supplementation positively improved ileal energy and crude protein digestibility, increased Lactobacillus counts, optimized intestinal morphology, enhanced intestinal digestive enzymes activities, and upregulated jejunal SGLT-1, GLUT-2, and PEPT-1 expression. Therefore, BPM supplementation improved growth performance of broiler chicks, which was partially related to the improvement in intestinal nutrient absorption capacity.

Triploidization modulates intestinal microbiota and promotes growth in Carassius auratus

Intestinal microbiota plays a key role in modulating host growth. However, the effect of triploidization on intestinal microflora and fast growth has not been fully explored. Here, autotriploid Carassius auratus (3nRR, 3n = 150) derived from Carassius auratus red var. (♀, RCC, 2n = 100) × autotetraploid fish (♂, 4nRR, 4n = 200) was established. Intestinal microbial community analysis of RCC and 3nRR was performed by 16S rRNA gene sequencing. Gut characteristics, growth rate, and digestive enzyme activity of the two groups of fish were explored. Significant changes in gut assemblages were observed in 3nRR fish. Differences in intestinal characteristics (structure, relative gut density, relative gut length, relative gut mass, and Zihler's index) were observed between RCC and 3nRR groups. Associations between microbial assemblages and intestinal characteristics were evaluated. Growth rate and activities of intestinal digestive enzymes (cellulase, amylase and trypsin) were higher in 3nRR compared with that in RCC. Spearman's correlation analysis showed a positive correlation between bacteria orders (Clostridiales, Micrococcales and Lactobacillales) and fast growth in 3nRR. In summary, the findings indicated that triploidization caused changes in gut microbiota and characteristics, and digestive enzyme activity. The relative abundance of several bacteria species was positively correlated with fast growth in 3nRR. The present study provided new insights into the growth mechanism of 3nRR and its interaction with intestinal microorganisms.

Intestinal response of Rana chensinensis larvae exposed to Cr and Pb, alone and in combination

Although numerous investigations on the adverse impact of Cr and Pb have been performed, studies on intestinal homeostasis in amphibians are limited. Here, single and combined effects of Cr (104 μg/L) and Pb (50 μg/L) on morphological and histological features, bacterial community, digestive enzymes activities, as well as transcriptomic profile of intestines in Rana chensinensis tadpoles were assessed. Significant decrease in the relative intestine length (intestine length/snout-to-vent length, IL/SVL) was observed after exposure to Pb and Cr/Pb mixture. Intestinal histology and digestive enzymes activities were altered in metal treatment groups. In addition, treatment groups showed significantly increased bacterial richness and diversity. Tadpoles in treatment groups were observed to have differential gut bacterial composition from controls, especially for the abundance of phylum Proteobacteria, Firmicutes, Verrucomicrobia, Actinobacteria, and Fusobacteria as well as genus Citrobacter, Anaerotruncus, Akkermansia, and Alpinimonas. Moreover, transcriptomic analysis showed that the transcript expression profiles of GPx and SOD isoforms responded differently to Cr and/or Pb exposure. Besides, transcriptional activation of pro-apoptotic and glycolysis-related genes, such as Bax, Apaf 1, Caspase 3, PK, PGK, TPI, and GPI were detected in all treatment groups but downregulation of Bcl2 in Pb and Cr/Pb mixture groups. Collectively, these results suggested that Cr and Pb exposure at environmental relevant concentration, alone and in combination, could disrupt intestinal homeostasis of R. chensinensis tadpoles.

Effects of dietary artemisinin on growth performance, digestive enzyme activity, intestinal microbiota, antioxidant capacity and immune biomarkers of Coral trout (Plectropomus leopardus)

Artemisinin is an active ingredient extracted from the Chinese medicine Artemisia carvifolia. The experiment investigated the effects of dietary artemisinin on growth performance, intestinal digestive enzyme activity and flora, antioxidant capacity, immune-related gene expression of Coral trout (Plectropomus leopardus). The 450 fish with an initial weight of 9.40 ± 0.04 g were randomly divided into 5 groups of 3 replicates and fed in 500 m3 fiberglass tank for 9 weeks. Five iso-nitrogenous (50% crude protein) and iso-lipidic (10% crude lipid) diets were formulated by supplementing various mass fractions of artemisinin (C0 0% as control; C0.2 0.20%, C0.4 0.40%, C0.8 0.80%, and C1.2 1.20%). The results showed that the C0.2 had the highest weight gain rate (WGR) compared to the others (P < 0.05). The levels of trypsin, amylase and lipase in the fish intestine reached their maximum values at C0.2 (P < 0.05). Compared to C0, feed supplementation with artemisinin significantly enhanced total antioxidant capacity in liver, intestine and serum, increased peroxidase, glutathione peroxidase, catalase and superoxide dismutase enzyme activities, and decreased malondialdehyde levels. The results of liver immune gene expression showed that tumor necrosis factor (TNFα), C-type lectin structural domain family 4 member M, myeloid differentiation factor 88 genes were significantly downregulated in the C0.8 group compared with the control group (P < 0.05). Analysis of the intestinal flora of C0, C0.2 and C1.2 showed that the supplementation of artemisinin reduced the relative abundance of conditionally pathogenic bacteria (Vibrio). In summary, dietary supplementation with artemisinin improved growth performance, enhanced nonspecific immunity and reduced the relative abundance of harmful flora in intestinal tract of Coral trout. Based on the quadratic regression analysis of WGR and dietary artemisinin levels, the recommended level of artemisinin supplements in the diet of Coral trout is 0.38%.

Effects of different probiotics (Bacillus subtilis) addition strategies on a culture of Litopenaeus vannamei in biofloc technology (BFT) aquaculture system

Augmenting biofloc systems with probiotics have been proven to improve water quality and enhance fish/shrimp performance. In this study, we aimed to evaluate the effects of different B. subtilis addition strategies in biofloc systems on water quality, Litopenaeus vannamei (L. vannamei) growth performance, and immune enzymes. Two probiotics addition methods were explored: addition to water group (A), addition via the aquafeed (B), and the control (C), in which no probiotics were applied. No significant differences were found in the means of NO2−-N between groups B and C, but both were significantly lower (p < 0.05) in NO2−-N than in group A (0.55 ± 0.12 mg/L). The mean NO3−-N concentration for group C (41.37 ± 2.45 mg/L) was the highest and the lowest for group A (37.84 ± 1.99 mg/L), among all treatments. The different addition methods did not influence the growth parameters of L. vannamei, except for the survival rate (SR), in which group A recorded the highest SR (93 ± 0.2%) (p < 0.05). It was found that irrespective of the addition strategy (groups A (5.35 ± 0.04 U/mgprot) and B (5.63 ± 0.06 U/mgprot)), probiotics application resulted in a significant increase in the intestinal pepsin of L. vannamei. The activity of catalase (CAT) and total antioxidant capacity (T-AOC) in the hepatopancreas were dependent on the addition method. However, SOD, ACP, and other immune parameters were independent of the addition method. The addition of Bacillus subtilis to the experimental system did not achieve a considerable growth effect of the growth performance of L. vannamei in BFT systems. Considering the two addition strategies, adding probiotics B. subtilis via the aquafeed was suggested, based on the corresponding effects on water quality, intestinal digestive enzyme activity, and non-specific immune enzymes activities of the shrimp.

Improvement of Flesh Quality of Farmed Silver Carp (Hypophthalmichthys molitrix) by Short-Term Stocked in Natural Water

To investigate the effects of different raising environments on the flesh quality, the study set up three groups of silver carp (Hypophthalmichthys molitrix), that is, pond-farmed; short-term stocked; and ranched, grown in a natural water ranch. This study compared the differences in muscle proximate composition and amino acid composition among three groups. The results showed that there was no difference between the ranched and the stocked groups in content of crude protein, ash, total amino acids (TAA), essential amino acids (EAA), and umami-flavored amino acids (UAA), with both groups being significantly higher than the farmed group. This shows that, in terms of flesh quality, the stocked group was closer to the ranched group and better than the farmed group after being stocked in natural water for 30 days. The results suggest that the flesh quality of farmed fish was improved by short-term stocking in natural water. To elucidate the reasons of flesh quality change in the stocked group, this study compared the food composition and intestinal digestive enzyme activity in three groups, demonstrating that the ranched and stocked groups had similar food composition, with their detritus proportion lower than that of the farmed group, consuming easily digestible phytoplankton diatoms rich in amino acids and fatty acids. No significant difference was seen between the ranched group and the stocked group, for which amylase, lipase, and trypsin activities were lower than that of the farmed group. It is hypothesized that differences in environmental and food composition resulted in lower digestive enzyme activity in the ranched group and the stocked group. In summary, the short-term stocking of farmed fish in a natural water ranch can effectively improve the nutrient content, quality and flavor, and promote value of fish products.

Effects of low-temperature stress on intestinal structure, enzyme activities and metabolomic analysis of juvenile golden pompano (Trachinotus ovatus)

Water temperature plays a crucial role in the growth, survival, and reproduction of fish species, as they make up the majority of aquatic fauna. In this study, the effects of low temperature were studied on the functional state of juvenile golden pompano (Trachinotus ovatus) under low-temperature stress. The study was conducted at 28°C in the control group and 18°C in the cold group for 14 d to determine the intestinal tissue, digestive and antioxidant enzyme activities, and metabolites of juvenile fish. The results showed that: (1) the swelling degree of the muscle layer deepened and was congested with a longer low-temperature stress period. The folds were sparse, from slight swelling to shedding and deformation. The intestinal mucosa was necrotic and had vacuoles, and the number gradually increased. Serious erosion of the villi occurred. (2) The specific activities of digestive enzymes showed a downward trend. (3) The intestinal superoxide dismutase (SOD) activity, malondialdehyde (MDA) content, and glutathione peroxidase (GSH-Px) activity showed an upward trend. The intestinal catalase (CAT) activity showed a downward trend. (4) Compared with the control group, there were 28 metabolites in the cold group showing significant differences, among which Z, 11Z, 14Z-eicosatrienoic acid, stearic acid, and adrenic acid showed an upward trend. In contrast, spermidine and uracil showed a downward trend. Among the enriched metabolic pathways, the main differential pathways were unsaturated fatty acid biosynthesis, fatty acid biosynthesis, linoleic acid metabolism, pyrimidine metabolism, and β-alanine metabolism. According to metabolomic analysis, under low-temperature stress, the fish body improved the synthesis of unsaturated fatty acids and saturated fatty acids to adapt to a low-temperature environment and consumed spermidine to improve its immune ability to clear the peroxide generated by the synthesis of unsaturated fatty acids in the body so that the cells were protected from oxidative damage. After 14 days, low-temperature stress affected metabolites and enzyme activity indices in juvenile golden pompano. Low-temperature stress causes changes in intestinal antioxidants and digestive enzymes and damage intestinal tissues. As a result of this exploration of how low temperatures affect the juvenile golden pompano, the foundation is laid for future studies, such as the molecular mechanisms of low-temperature adaptation in fish species.

Effect of Quercetin Nanoparticles on Hepatic and Intestinal Enzymes and Stress-Related Genes in Nile Tilapia Fish Exposed to Silver Nanoparticles.

Recently, nanotechnology has become an important research field involved in the improvement of animals' productivity, including aquaculture. In this field, silver nanoparticles (AgNPs) have gained interest as antibacterial, antiviral, and antifungal agents. On the other hand, their extensive use in other fields increased natural water pollution causing hazardous effects on aquatic organisms. Quercetin is a natural polyphenolic compound of many plants and vegetables, and it acts as a potent antioxidant and therapeutic agent in biological systems. The current study investigated the potential mitigative effect of quercetin nanoparticles (QNPs) against AgNPs-induced toxicity in Nile tilapia via investigating liver function markers, hepatic antioxidant status, apoptosis, and bioaccumulation of silver residues in hepatic tissue in addition to the whole-body chemical composition, hormonal assay, intestinal enzymes activity, and gut microbiota. Fish were grouped into: control fish, fish exposed to 1.98 mg L-1 AgNPs, fish that received 400 mg L-1 QNPs, and fish that received QNPs and AgNPs at the same concentrations. All groups were exposed for 60 days. The moisture and ash contents of the AgNP group were significantly higher than those of the other groups. In contrast, the crude lipid and protein decreased in the whole body. AgNPs significantly increased serum levels of ALT, AST, total cholesterol, and triglycerides and decreased glycogen and growth hormone (*** p < 0.001). The liver and intestinal enzymes' activities were significantly inhibited (*** p < 0.001), while the oxidative damage liver enzymes, intestinal bacterial and Aeromonas counts, and Ag residues in the liver were significantly increased (*** p < 0.001, and * p < 0.05). AgNPs also significantly upregulated the expression of hepatic Hsp70, caspase3, and p53 genes (* p < 0.05). These findings indicate the oxidative and hepatotoxic effects of AgNPs. QNPs enhanced and restored physiological parameters and health status under normal conditions and after exposure to AgNPs.

Effects of Tributyrin Supplementation on Growth Performance, Intestinal Digestive Enzyme Activity, Antioxidant Capacity, and Inflammation-Related Gene Expression of Large Yellow Croaker (Larimichthys crocea) Fed with a High Level of Clostridium autoethanogenum Protein.

An 8-week growth experiment was conducted to investigate effects of tributyrin (TB) supplementation on growth performance, intestinal digestive enzyme activity, antioxidant capacity, and inflammation-related gene expression of juvenile large yellow croaker (Larimichthys crocea) (initial weight of 12.90 ± 0.02 g) fed diets with high level of Clostridium autoethanogenum protein (CAP). In the negative control diet, 40% fish meal was used as the major source of protein (named as FM), while 45% fish meal protein of FM was substituted with CAP (named as FC) to form a positive control diet. Based on the FC diet, grade levels of 0.05%, 0.1%, 0.2%, 0.4%, and 0.8% tributyrin were added to formulate other five experimental diets. Results showed that fish fed diets with high levels of CAP significantly decreased the weight gain rate (WGR) and specific growth rate (SGR) compared with fish fed the FM diet (P < 0.05). WGR and SGR were significantly higher than in fish fed diets with 0.05% and 0.1% tributyrin that fed the FC diet (P < 0.05). Supplementation of 0.1% tributyrin significantly elevated fish intestinal lipase and protease activities compared to FM and FC diets (P < 0.05). Meanwhile, compared to fish fed the FC diet, fish fed diets with 0.05% and 0.1% tributyrin showed remarkably higher intestinal total antioxidant capacity (T-AOC). Malondialdehyde (MDA) content in the intestine of fish fed diets with 0.05%-0.4% tributyrin was remarkably lower than those in the fish fed the FC diet (P < 0.05). The mRNA expressions of tumor necrosis factor α (tnfα), interleukin-1β (il-1β), interleukin-6 (il-6), and interferon γ (ifnγ) were significantly downregulated in fish fed diets with 0.05%-0.2% tributyrin, and the mRNA expression of il-10 was significantly upregulated in fish fed the 0.2% tributyrin diet (P < 0.05). In regard to antioxidant genes, as the supplementation of tributyrin increased from 0.05% to 0.8%, the mRNA expression of nuclear factor erythroid 2-related factor 2 (nrf2) demonstrated a trend of first rising and then decreasing. However, the mRNA expression of Kelch-like ECH-associated protein 1 (keap1) was remarkably lower in fish fed the FC diet than that fed diets with tributyrin supplementation (P < 0.05). Overall, fish fed tributyrin supplementation diets can ameliorate the negative effects induced by high proportion of CAP in diets, with an appropriate supplementation of 0.1%.

The Impacts of Dietary Curcumin on Innate Immune Responses and Antioxidant Status in Greater Amberjack (Seriola dumerili) under Ammonia Stress

In this study, we investigated the effect of dietary curcumin on non-specific immune responses and antioxidative ability in Seriola dumerili under ammonia stress and post-recovery. Three diets were prepared to contain 0, 75, and 150 mg/kg of curcumin. A total of 225 greater amberjack (initial weight: 100.90 ± 0.03 g) were distributed into nine cylindrical tanks, constituting an experimental design with three treatments and three replicates. After 56 days of feeding, plasma, intestinal, and hepatic enzyme activities were evaluated. Then, an acute ammonia challenge experiment was conducted. Ten fish per tank were subjected to acute ammonia stress (total ammonia-N: 1000 mg/L) for eight minutes followed by six minutes of recovery. The results indicated that dietary curcumin significantly promoted intestinal and hepatic alkaline phosphatase (ALP) and acid phosphatase (ACP) levels as well as hepatic antioxidative enzymes such as superoxide dismutase (SOD), total antioxidant capacity (T-AOC), reduced glutathione (GSH), and glutathione peroxidase (GSH-Px) of greater amberjack. In addition, curcumin addition improved the activities of antioxidant enzymes, such as SOD, T-AOC, GSH, GSH-Px, and catalase (CAT), and reduced malondialdehyde (MDA) content in liver, spleen, head kidney, and brain tissues after post-recovery. The indexes related to immunity and antioxidant enzymes in the liver, gill, and spleen rose again to some extent, but they showed the worst recovery ability in the head kidney and brain tissue samples. These results indicate that dietary curcumin supplementation could increase non-specific immune responses, antioxidant ability, and enhance resistance to high ammonia stress in juvenile S. dumerili.

Dietary leucine requirement of fingerling Channa punctatus (Bloch) based on growth, feed conversion and leucine retention efficiency, hematological parameters, antioxidant and intestinal enzyme activities.

To find out the dietary leucine requirement of fingerling Channa punctatus (5.24 ± 0.07g), six purified experimental diets (45% CP and 14.73kJ/g DE) with various leucine concentrations (0.5, 1.0,1.5, 2.0, 2.5 and 3.0% diet) were fed to apparent satiation to triplicate groups for 12weeks (714/02/a/CPCSEA). Absolute weight gain, specific growth rate, feed conversion ratio, protein efficiency ratio, protein and leucine retention efficiency, and RNA/DNA ratio improved up to 2.0% leucine in the diet. Carcass protein and fat increased significantly with increasing leucine levels up to a 2.0% dry diet. Moisture content showed a reverse pattern. Red blood corpuscles hemoglobin and hematocrit increased with incremental levels of leucine up to 2.0% diet. Significant changes were also noted in serum total protein, superoxide dismutase, aspartate aminotransferase, alanine aminotransferase, and lysozyme activity. Serum protein, superoxide dismutase and lysozyme activity were positively correlated with increasing leucine levels up to 2.0% diet, whereas aspartate aminotransferase and alanine aminotransferase showed the opposite trend. Based on the quadratic regression analysis of absolute weight gain, specific growth rate, feed conversion ratio, protein, and leucine retention efficiency, inclusion of 2.0% leucine is recommended for optimum growth of fingerling C. punctatus.