Mid Intestine Research Articles

Characterization of thermostable amylases of the mid intestine gland of Ucides Cordatus and its potential use as an enzymatic biosensor for mercury

Amylases are enzymes that represent approximately 25% of the global enzymatic market, presenting a widespread biotechnological application. This study aimed at extracting, purifying, and characterizing the amylases from the mid intestine gland (MIG) of Ucides cordatus to evaluate their sensitivity to metallic ions as a source of enzymes for environmental monitoring. The crude extract obtained from the MIG was subjected to a partial two-step purification: thermal treatment and precipitation with ammonium sulfate in two fractions (F1: 0-30% and F2: 30-60%). F2 was incubated in different substrates. After observing the high amylolytic activity in this fraction when compared to the other substrates, characterization was performed. The optimum temperature for F2 varied between 45 and 55ºC and the optimum pH between 6 and 7. Protein molecular masses for F2 were estimated to be between 30-34 kDa. F2 amylolytic activity was activated in the presence of 0.0001 mM of Cu+2 (14.5%), Mg+2 (13.29%), Na+ (12.66%), Ca+2 (11.04%), Fe+2 (6%) and inhibited by 0.0001 mM of Cd+2 (22.38%) and Hg+2 (95%). Due to having its activity strongly inhibited by mercury, we suggest the potential use of this fraction as a biological component as a biosensor for heavy metal monitoring.

Potential protective effects of sodium butyrate on glycinin-induced oxidative stress, inflammatory response, and growth inhibition in Cyprinus carpio.

Investigated mitigating effects of sodium butyrate (SB) on the inflammatory response, oxidative stress, and growth inhibition of common carp (Cyprinus carpio) (2.94 ± 0.2g) are caused by glycinin. Six isonitrogenous and isoenergetic diets were prepared, in which the basal diet was the control diet and the Gly group diet contained 80g/kg glycinin, while the remaining 4 diets were supplemented with 0.75, 1.50, 2.25, and 3.00g/kg SB, respectively. The feeding trial lasted for 8weeks, and the results indicated that supplementing the diet with 1.50-2.25g/kg of SB significantly improved feed efficiency and alleviated the growth inhibition induced by glycinin. Hepatopancreas and intestinal protease activities and the content of muscle crude protein were significantly decreased by dietary glycinin, but supplement 1.50-2.25g/kg SB partially reversed this result. SB (1.50-2.25g/kg) increased the activities of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in the hepatopancreas and reduced the activities of AST and ALT in the serum. Glycinin significantly reduced immune and antioxidant enzyme activities, whereas 1.50-2.25g/kg SB reversed these adverse effects. Furthermore, compared with the Gly group, supplement 1.50-2.25g/kg SB eminently up-regulated the TGF-β and IL-10 mRNA, and down-regulated the IL-1β, TNF-α, and NF-κB mRNA in hepatopancreas, mid-intestine (MI), and distal intestine (DI). Meanwhile, supplement 1.50-2.25g/kg SB activated the Keap1-Nrf2-ARE signaling pathway and upregulate CAT, SOD, and HO-1 mRNA expression in hepatopancreas, MI, and DI. Summarily, glycinin induced inflammatory response, and oxidative stress of common carp ultimately decreased the digestive function and growth performance. SB partially mitigated these adverse effects by activating the Keap1-Nrf2-ARE signaling pathway and inhibiting the NF-κB signaling pathway.

Translocation of 14C-polystyrene nanoplastics into fish during a very-low concentration dietary exposure

Assessing the dietary accumulation of nanoplastics in animals following very-low exposure concentrations is restricted due to analytical limitations. This study adapted a method for synthesising semi-stable 14C-PS NPs (through styrene polymerisation) in small volumes for deployment in environmental studies. The method was developed with non-labelled material where the final polystyrene product had a primary particle size of 35 ± 8 nm (as measured by transmission electron microscopy). This method was then applied to 14C-labelled styrene to produce radiolabelled polystyrene nanoplastics (14C-PS NPs). The 14C-PS NPs were added (top-dressed) to a commercially available fish feed, with a measured concentration of 27.9 ± 2.1 kBq kg−1 (n = 5), equating to 5.9 μg polystyrene kg−1 feed. Fish (rainbow trout; Oncorhynchus mykiss) were fed this diet at a ration of 2% body weight per day for a period of two weeks. On day 3, 7 and 14, the fish were sampled for the mid intestine, hind intestine, kidney and liver, and measured for tissue radioactivity (determined by liquid scintillation counting). Some background activity was detected in the control samples (e.g., 1–16 and 4–11 Bq g−1 in the hind intestine and liver, respectively) which is due to natural background fluorescence. By the end of the experiment, the hind intestine and liver had significantly elevated radioactivity (25.3 and 15.0 Bq g−1, respectively) compared to the control, indicating the accumulation of nano polystyrene. In the liver, this equated to 1.8 μg polystyrene g−1 dry weight. This study confirms the accumulation of nano particles in vertebrates at low, environmentally relevant concentration, and highlights radiolabelling as a methodological approach suitable for exploring the bioaccumulation of nanoplastics and potential impacts.

An in-depth characterisation of European seabass intestinal segments for assessing the impact of an algae-based functional diet on intestinal health

Sustainable farming of fish species depends on emerging new feed ingredients, which can alter the features of the digestive tract and influence animals’ overall health. Recent research has shown that functional feeds hold great potential for enhancing fish robustness by evoking appropriate responses at the intestine level. However, there is a lack of extensive and accurate descriptions of the morphology of the gastrointestinal tract of most farmed fish. We have characterised the intestine of European seabass thoroughly, by targeting four segments − anterior, mid, posterior and rectum. Results indicated that the anterior segment is mostly associated with absorption-related features; this segment has the largest absorptive area, the longest villi, and the highest number of neutral goblet cells (GC). The posterior segment and rectum have distinct histomorphometric features, but both seem to be important for immunity, displaying the highest count of acid GC and the highest expression of immune-related genes. The strongest proliferating cell nuclear antigen (PCNA) signal was observed in the anterior intestine and rectum, with PCNA+ cells appearing at the base of the villi and the corresponding villi branches. We have also evaluated the impact of a novel feed supplemented with a macro- and microalgae blend and found that there were no differences in terms of growth. However, the alterations observed in the mid intestine of fish fed the blend, such as thickening of the submucosa and lamina propria, an increased number of leucocytes, and higher expression of immune- and oxidative stress-related genes, suggest that algae may have an immunomodulatory effect. In the current article, we have described the morphology and expression patterns of the intestine segments of European seabass in detail and have presented a comprehensive report of the indices and methods used for the semi-quantitative and quantitative histomorphometric assessments, thereby providing useful information for future studies that aim to maintain intestinal health through dietary interventions.

Fucoidan from Undaria pinnatifida mitigates intestinal inflammation in Atlantic salmon (Salmo salar)

Using functional feed ingredients to increase the intestinal health of Atlantic salmon (Salmo salar) could allow greater variation and higher inclusion of plant-based proteins in the feed. This is beneficial both for the fish feed industry and fish welfare. Components with strong bioactive properties, such as fucoidans from marine macroalgae, have a great potential as a functional feed ingredient. In the present trial, we challenged Atlantic salmon (Salmo salar) post-smolts with 17.8% soya HP48, a diet that has been shown to cause low-level intestinal inflammation. Fucoidan from Undaria pinnatifida was included at 0, 1, or 3% (Control, FUC1, and FUC3, respectively) to study its ability to alleviate this low-level inflammation . The fish were fed the diets in triplicate tanks for 59 days. At the end of the experiment, the fish were euthanised and the mid- and hind intestine were sampled for morphological-, integrity- (Ussing chamber) and gene expressional- (RNAseq) assessments. Addition of 3% fucoidan lowered the protein digestibility of the feed, however, this did not result in significant differences in the growth parameters. The paracellular permeability of the hydrophilic marker 14C-mannitol tended to decrease with the addition of fucoidan in both tissue segments. The active transport of l-lysine in the mid intestine was significantly reduced in a dose-dependent manner of fucoidan. An anti-inflammatory effect of fucoidan was observed in the hind intestine with significant reductions in the stratum granulosum width and lamina propria height of fish fed FUC1 and FUC3 compared to the Control. This suggests that U. pinnatifida fucoidan can have positive effect on both intestinal integrity and immune regulation of Atlantic salmon (Salmo salar).

Dietary α-ketoglutarate alleviates glycinin and β-conglycinin induced damage in the intestine of mirror carp (Cyprinus carpio).

This study investigated the glycinin and β-conglycinin induced intestinal damage and α-ketoglutarate alleviating the damage of glycinin and β-conglycinin in intestine. Carp were randomly divided into six dietary groups: containing fish meal (FM) as the protein source, soybean meal (SM), glycinin (FMG), β-conglycinin (FMc), glycinin+1.0% α-ketoglutarate (AKG) (FMGA), β-conglycinin+1.0% AKG (FMcA). The intestines were collected on 7th, and the hepatopancreas and intestines were collected on 56th. Fish treated with SM and FMc displayed reduced weight gain, specific growth rate, and protein efficiency. On 56th day, Fish fed on SM, FMG and FMc presented lower superoxide dismutase (SOD) activities. FMGA and FMcA had higher SOD activity than those fed on the FMG and FMc, respectively. In intestine, fish fed on the SM diets collected on 7th presented upregulated the expression of transforming growth factor beta (TGFβ1), AMP-activated protein kinase beta (AMPKβ), AMPKγ, and acetyl-CoA carboxylase (ACC). Fish fed FMG presented upregulated expression of tumor necrosis factor alpha (TNF-α), caspase9, and AMPKγ, while downregulated the expression of claudin7 and AMPKα. FMc group presented upregulated expression of TGFβ1, caspase3, caspase8, and ACC. Fish fed FMGA showed upregulated expression of TGFβ1, claudin3c, claudin7, while downregulating the expression of TNF-α and AMPKγ when compared to fish fed FMG diet. FMcA upregulated the expression of TGFβ1, claudin3c than fed on the FMc. In intestine, the villus height and mucosal thickness of the proximal intestine (PI) and the distal intestine (DI) were decreased and crypt depth of the PI and mid intestine (MI) were increased in SM, FMG and FMc. In addition, fish fed on SM, FMG and FMc presented lower citrate synthase (CS), isocitrate dehydrogenase (ICD), α-ketoglutarate dehydrogenase complex (α-KGDHC) Na+/K+-ATPase activity in DI. FMGA had higher CS, ICD, α-KGDHC, and Na+/K+-ATPase activity in PI and MI than those fed on the FMG. FMcA had higher Na+/K+-ATPase activity in MI. In conclusion, dietary soybean meal destroys the intestine's health, the adverse effects are related to the presence of β-conglycinin and glycinin, especially glycinin. AKG may regulate intestinal energy via tricarboxylic acid cycle, thereby alleviating the damage intestinal morphology caused by the dietary soybean antigen proteins.

Dietary chitosan alleviates intestinal and liver injury of hybrid sturgeon (Acipenser baerii♀ × A. schrenckii♂) induced by Aeromonas hydrophila infection

Chitosan has been universally used as a feed additive, whereas its regulation on hybrid sturgeon (Acipenser baerii♀ × Acipenser schrenckii♂) after bacterial infection has not been well studied. This study was conducted to investigate the therapeutic intervention with dietary chitosan on alleviating intestinal and liver injury of hybrid sturgeon induced by Aeromonas hydrophila infection. Healthy sturgeons were pre-challenged by treating with A. hydrophila supplemented diets for 1 week and then fed with diets containing different levels (0.00, 1.00, 3.00 and 5.00 g/kg) of chitosan for 8 weeks. The results showed that there were significant differences (P < 0.05) of FBW, WG, SGR, FI and FCR in sturgeon fed chitosan diets compared to those in fish fed the control diet. Significant enhancement (P < 0.05) of LZM, ACP, AKP and MPO activities were observed in all fish serum therapeutically administrated with chitosan. Compared to control diet, the CAT, SOD and GSH-Px capacity were significantly increased (P < 0.05), and the MDA content was decreased in liver of sturgeons fed chitosan supplemented diets. Moreover, not only mitigate tissue lesions in the liver and intestine, but also visible increase (P < 0.05) of goblet cells in fish mid intestine as well as evident increase (P < 0.05) of the muscular thickness and villus height (except in group CHI1) in fish spiral valve were observed after therapeutic chitosan supplementation. The fish therapeutically administrated with 1.00, 3.00 and 5.00 g/kg chitosan conferred 50.00%, 75.00%, 62.50% relative percent survival, respectively, for hybrid sturgeons pre-challenged with A. hydrophila. These results suggested that therapeutic administration of chitosan by sturgeon not only increases their growth performance, antioxidant activity and non-specific immunity but also alleviates intestinal and liver injury in fish challenged by A. hydrophila.

Beneficial Effects of Graded Levels of Fish Protein Hydrolysate (FPH) on the Growth Performance, Blood Biochemistry, Liver and Intestinal Health, Economics Efficiency, and Disease Resistance to Aeromonas hydrophila of Pabda (Ompok pabda) Fingerling

Fish protein hydrolysate (FPH) is the enzymatic hydrolysis of protein into smaller peptide and free amino acids, which has recently captured considerable attention as a supplementary ingredient in the aqua-feed industry sector. The present research aimed to observe the physiological, biochemical, and bacteriological study of FPH-treated diets and its effects on growth, hematology, plasma biochemistry, liver and gut histopathology, and resistance to Aeromonas hydrophila infection in Pabda (Ompok pabda). Four experimental diets (35% crude protein) were formulated with graded FPH supplementation (0, 0.5, 1, and 2%). The feed physiological parameters such as expansion ratio, bulk density, water stability, and floatability were not significantly affected by dietary FPH levels (p &gt; 0.05), except for the pellet durability index (PDI). Furthermore, the diets with 1% and 2% FPH were more palatable to fish than other treatment diets. The total bacteria (TB) in fish diets and guts followed an increasing trend with the increase in various levels of FPH in diets. The significantly highest body weight, specific growth rate (SGR), total biomass (TB), survival rate (SR), condition factor (CF), and hepatosomatic index (HSI) were noted in 2% FPH-fed fish when compared with other treatment groups (p &lt; 0.05). The feed intake of fish was significantly increased when increasing the FPH in diets (p &lt; 0.05). The fish fed with a 2% FPH diet had significantly higher neutrophil, monocyte, lymphocyte, red blood cell, and platelet levels (p &lt; 0.05). The blood glucose, creatinine, total protein, and globulin were significantly lower in control fish compared to other treatment groups (p &lt; 0.05). The histopathological observation of mid intestine tissues displayed that 2% of FPH-diet-fed fish had a well-anchored epithelial wall with well-arranged goblet cells, a long villus structure, stratum compactum, and tunica muscularis compared to other treatments of FPH. The inclusion of FPH in diets up to 2% significantly improved the liver health of fish. The fish fed with 2% FPH had a significantly lower cumulative percent mortality (16.67%) against A. hydrophila infection in the bacterial challenge test (p &lt; 0.05). Therefore, the present results suggested that using 2% FPH in the aqua-feed industry improves the growth performance, health status, and disease resistance of Pabda fingerlings in captivity.

Effects of dietary yeast hydrolysate on the growth performance, intestine health and digestion of juvenile yellow catfish (Pelteobagrus vachelli ♂ × Pelteobagrus fulvidraco ♀)

The effects of dietary yeast hydrolysate on the growth performance, gut health, and digestion of juvenile yellow catfish were evaluated throughout a 62-day feeding trial. Isonitrogenous and isoenergetic experimental diets were prepared. The positive control fishmeal (FM) diet contained 40 % FM. The negative control plant protein diet (PM group) contained 18 % soybean meal (SBM) and 18 % rapeseed meal (RSM). In other two test diets, 1 % and 5 % of yeast hydrolysate (1 % YH and 5 % YH group) were used to replace SBM and RSM (1:1) of PM group, respectively. The results showed no significant differences in the growth performance of yellow catfish among all groups. However, daily food intake was significantly increased in 5 % YH compared with the control PM. Besides, the apparent digestibility coefficient (ADC) of dry matter improved in 1 % YH, compared with FM. And the YH groups had significantly higher total EAA concentrations in plasma than PM group. The 1 %−5 % YH supplement in plant protein diet could improve the length of gut villi and density of distal intestinal microvilli, and enhance the antioxidant capacity of mid intestine and distal intestine. Compared with PM, YH groups increased the digestive capacity of proximal intestine and mid intestine. It is concluded that 1 %−5 % of dietary yeast hydrolysate improved intestine health, food consumption and absorptive ability of yellow catfish.

Dietary β-conglycinin induces intestinal enteritis and affects glycerophospholipid and arginine metabolism in mirror carp (Cyprinus carpio)

The use of soybean meal in aquafeed industry is partially limited by anti-nutritional factors such as β-conglycinin (β-CG). However, the effects of β-CG on mirror carp (Cyprinus carpio) growth performance and intestinal health has not been elucidated. This study investigated the effects of β-CG levels on growth performance, intestine immunity, and intestinal lipid and protein metabolism in mirror carp. Four hundred and fifty mirror carp (4.22 ± 0.03) g were fed a control (CON) diet containing fish meal as the protein source and four experimental diets containing β-CG at 40 (β-CG1), 80 (β-CG2), 120 (β-CG3), and 160 g/kg (β-CG4) replacing the fishmeal, respectively. Each treatment had 30 fish replicated three times and the feeding was done for six weeks. The results showed that weight gain, specific growth rate, survival rate, protein efficiency, feed conversion ratio, and condition factor were not affected by dietary β-CG (P > 0.05). Interestingly, the fish fed on the β-CG diets upregulated significantly the expression of tumor necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1β) and eIF4E-binding protein (4E-BP) in the proximal intestine (PI) than those fed on the CON diet (P < 0.05). The fish fed on the β-CG2 diet decreased significantly the expression of transforming growth factor beta 1 (TGFβ1) in the PI compared to those fed on the CON diet. The fish fed on the β-CG diets downregulated significantly the expression of target of rapamycin (TOR) in the PI than those fed on the CON diet. The fish fed on β-CG diets downregulated significantly the expression of AMP-activated protein kinase alpha (AMPK), acetyl-CoA carboxylase (ACC), TOR in the mid intestine (MI) while, claudin11 gene was significantly increased (P < 0.05). In the distal intestine (DI), feeding the fish on the β-CG diets downregulated significantly the expression of AMPK and ACC genes, while increased the expression TNF-α, IL-1β and claudin11 (P < 0.05). Feeding the fish with the β-CG diets mostly altered glycerophospholipid metabolism and arginine biosynthesis in intestinal mucosa. These results suggest that dietary β-CG induces enteritis in different intestinal segments and changes glycerophospholipid metabolism and arginine biosynthesis pathways. Fish farmers using soybean meal in the diets should process the ingredients to reduce β-CG concentration before use.

Dietary chitosan moderates the growth rate, antioxidant activity, immunity, intestinal morphology and resistance against Aeromonas hydrophila of juvenile hybrid sturgeon (Acipenser baerii♀ × Acipenser schrenckii♂)

This study investigated the effects of dietary chitosan on growth, antioxidant, immunity, intestinal morphology and resistance against Aeromonas hydrophila of hybrid sturgeon (Acipenser baerii♀ × Acipenser schrenckii♂). Sturgeons (18.18 ± 0.08 g) were randomly divided into four groups, fed with chitosan-supplemented diets for 8 weeks and then infected with A. hydrophila. The results showed significant differences of body weight gain, specific growth rate and feed conversion ratio in sturgeon fed chitosan and control diets. The oral administration of chitosan significantly increased the acid phosphatase, alkaline phosphatase, lysozyme, myeloperoxidase, superoxide dismutase, glutathione peroxidase and catalase activities, as well as the complement 3 and 4 contents and disease resistance against A. hydrophila. Moreover, enhancement of muscular thickness and goblet cells in mid intestine and increase of muscular thickness and villus height in spiral valve were observed in the chitosan supplemented groups. In addition, dietary chitosan-supplemented diets mitigated the changes of antioxidant and immune activity induced by A. hydrophila challenge, as well as prevented fish from bacterial invasion. The optimal dose was 3.00 g chitosan/kg diet for hybrid sturgeon.

Uptake, distribution and elimination of palladium-doped polystyrene nanoplastics in rainbow trout (Oncorhynchus mykiss) following dietary exposure

The ingestion of nanoplastics (NPs) by fish has led to concerns regarding fish health and food chain transfer, but analytical constraints have hindered quantitative data collection on their uptake and depuration. We used palladium-doped polystyrene nanoplastics (PS-Pd NPs, ~200 nm) to track particle fate in rainbow trout (Oncorhynchus mykiss) during a week-long dietary exposure and subsequent 7-day depuration period on a control diet (no added PS-Pd NPs). At Day 3 and 7 of the exposure, and after depuration, the mid intestine, hind intestine, liver, gallbladder, kidney, gill and carcass were sampled. All organs and the carcass were analysed for total Pd content by inductively couple plasma mass spectrometry. After 3 days of exposure, the mid (32.5 ± 8.3 ng g−1) and hind (42.3 ± 8.2 ng g−1) intestine had significantly higher total Pd concentrations compared to the liver and carcass (1.3 ± 0.4 and 3.4 ± 1.1 ng g−1, respectively). At Day 7, there was no time-related difference in any organ (or the carcass) total Pd concentrations compared to Day 3. When the total Pd content was expressed as a body distribution based on mass of tissue, the carcass contained the highest fraction with 72.5 ± 5.2 % at Day 7, which could raise concerns over transfer to higher trophic levels. The total number of particles that entered the fish over the 7 days was 94.5 ± 13.5 × 106 particles, representing 0.07 ± 0.01 % of the Pd the fish had been fed. Following depuration, there was no detectable Pd in any organ or the carcass, indicating clearance from the fish. These data indicate that these NPs are taken into the internal organs and carcass of fish, yet removal of the exposure results in substantial excretion to below the limit of detection.

Distinctive location of piscine intestinal coccidiosis in Asian seabass fingerlings.

Coccidian infection (coccidiosis) is one of the most important causes of illness and death in the fish population, including Asian sea bass. The fingerling developmental stage is sensitive to various infectious agents. Economic losses are sustained by the sea bass aquaculture industry due to coccidiosis annually. However, the related pathological changes in the Asian sea bass fingerlings' three-part intestine remain unknown. This study aimed to investigate the Asian sea bass fingerlings' infection rate, infection location and site, and specific pathological lesions in the small intestinal tissues in a marine cage farming operation. A cross-sectional study was conducted on 44 fingerling fishes. Major coccidia proportions were identified morphologically at both the macroscopic and microscopic levels. The infection number was determined based on coccidia presence at various intestinal locations and sites. All areas were assessed for pathological lesions using semi-quantitative grading. Analysis of variance was used to perform all data analyses using the SPSS software. Data were expressed as means ± standard deviation. p < 0.05 was considered statistically significant. All Asian sea bass fingerlings studied were infected with coccidia. Enteritis and mucosal necrosis were distinct lesions found in the anterior intestine, which had the highest infection rate (49.94%), followed by the mid intestine (35.63%), and the posterior intestine (22.43%). The most common coccidian infection site was extracellular (subepithelial), followed by intracytoplasmic, and epicellular sites. Histopathological lesion determination revealed that intestinal tissue inflammation and epithelial injuries were predominantly seen in the anterior gut (p < 0.05). There was a high coccidian infection rate in Asian sea bass fingerlings from marine cage farming operations. Infection and intestinal damage at the anterior intestine, a major site, led to fingerling death. Disease prevention in the nursery should be intensive from the fingerling period to decrease the fatality rate caused by coccidia.

Effect of dietary NSP level and bile acid supplementation on nutrient digestibility and the bile acid metabolism in rainbow trout (Oncorhynchus mykiss)

The effects of dietary bile acid supplementation (BAS) on apparent digestibility coefficients (ADC) and the bile acid metabolism in rainbow trout (Oncorhynchus mykiss) were investigated for diets differing in non-starch polysaccharide (NSP) level. Four experimental diets were formulated according to an 2 by 2 factorial design. A low-NSP and High-NSP diet (0 vs. 160 g kg−1 inclusion of an NSP-rich ingredient mixture) were first formulated. The aim of this was to create differences in the amount of faecal waste produced, and consequently as previously shown in rainbow, the amount of faecal bile acid loss (FBAL). Both NSP-level diets were tested with 0% and 0.3% BAS (0 vs. 3 g kg−1 inclusion of a bile acid mixture). The bile acid mixture contained taurocholic acid (T-CA) and glycocholic acid (G-CA) in a 2:1 ratio. Glycocholic acid does not naturally occur in trout and was used as marker to see if supplemented bile acids are efficiently absorbed and enter enterohepatic circulation (EHC). Fish were fed to apparent satiation for 42 days. Dietary NSP level did not enhance FBAL. BAS was beneficial for fat ADC, but not for the ADC of protein and carbohydrates. BAS improved fat ADC regardless of NSP level, which suggests that bile acids are a limiting factor for fat digestion in rainbow trout. Total bile acid synthesis was a 4-fold lower in fish fed the 0.3% BAS diets compared to the 0% BAS diets. Lower bile acid synthesis with BAS occurred alongside enlarged body and liver + gallbladder bile acid pools and a higher content of bile acids in the chyme. These higher bile acid levels most likely caused a negative feedback inhibition of bile acid synthesis. Negative synthesis rates of G-CA were found when feeding the 0.3% BAS diets, which suggests that this bile acid is catabolised or converted into other bile acid types in rainbow trout. The enlarged pool of T-CA, but especially of the body foreign G-CA, with BAS in both the body and liver + gallbladder shows that dietary bile acids are effectively taking part in EHC. The relative absorption of T-CA and G-CA over the different intestinal compartments was comparable, which shows that EHC does not differentiate between T-CA and G-CA. While relative absorption of bile acids was highest between the distal intestine and the faeces, the absolute decrease in chyme bile acid content was highest between the pyloric region and the mid intestine. The latter shows that significant bile acid absorption occurs more proximal in the intestine of rainbow trout than previously thought.

Alleviative effect of biofloc technology (BFT) on extruded soybean meal (ESBM)-induced growth inhibition and intestinal barrier dysfunction in Rhynchocypris lagowskii

This study evaluated the alleviative effect of bioflocs technology (BFT) on intestinal morphology, permeability, digestive function, immune function, antioxidant capacity and microbiota of Rhynchocypris lagowskii sensitized by extruded soybean meal (ESBM). In a 2 × 2 factorial design, R. lagowskii (6.40 ± 0.01 g) was randomly divided into 4 groups, which contains two culture modes (traditional mode and biofloc mode) and two levels of dietary ESBM (0% and 68%). At the end of the experiment (8 weeks), the results showed that the growth performance of R. lagowskii was significantly increased by BFT, but significantly decreased by feeding diets with 68% ESBM (P < 0.05). Culture mode significantly affected intestinal growth indexes, morphology, the levels of tight junction protein mRNA, the activities of digestive enzymes, immune function, inflammation response and antioxidant capacity in proximal intestines (PI), mid intestines (MI) and distal intestines (DI) (P < 0.05). These indexes (except fold height, lamina propria width, the levels of tight junction protein mRNA, the activities of protease, AKP and LZM, the levels of inflammation related mRNA, the levels of T-SOD and PC, the levels of Nrf2, Keap1, HO-1 and Maf mRNA in PI, the activities of CAT in MI, the activities of lipase and amylase in intestines) were also significantly affected the levels of dietary ESBM (P < 0.05). Intestinal permeability (DAO, 5-HT, ET-1 and D-LA) were only significantly affected by the levels of dietary ESBM (P < 0.05). In addition, the interaction between culture mode and the levels of dietary ESBM was observed for muscular layer thickness and T-AOC in PI, fold height, ZO-1, NF-κB and Nrf2 in MI, Claudin-2, IL-1β, TGF-β, T-AOC, Nrf2, HO-1 and Maf in DI (P < 0.05). Results of intestinal microbiota showed that relative abundance of Amaricoccus, Aquitalea, Chelatococcus and Nakamurella were significantly affected by culture mode, the levels of ESBM in diets and their interaction (P < 0.05). Therefore, this study indicated that intestinal morphology, permeability, digestive function, immune function, antioxidant capacity and microbiota in R. lagowskii could be affected by ESBM and alleviated by BFT.

Effects of partial replacement of fish meal with porcine meat meal on growth performance, antioxidant status, intestinal morphology, gut microflora and immune response of juvenile golden pompano (Trachinotus ovatus)

This study was conducted to investigate the effects of partial replacement of fish meal (FM) with porcine meat meal (PMM) on growth performance, plasma antioxidant parameters, intestine morphological parameters, gut microflora and expression of intestinal Nrf2 and Nf-κB signaling pathway of juvenile golden pompano. Fish were fed with six experimental diets (0 (PC), 10% (P10), 20% (P20), 30% (P30), 40% (P40) and 50% (P50) replacement levels) for 8-weeks. The percent weight gain and specific growth rate in fish fed with P40 and P50 diets were significantly lower than those of the control group (P < 0.05). Compared with the control group, the plasma antioxidant indexes including the activities of superoxide dismutase, catalase, glutathione peroxidase, total antioxidant capacity and malondialdehyde content in fish fed with P30, P40 and P50 diets were significantly affected (P < 0.05). With dietary replacement of FM with PMM increasing 0 to 30%, the relative expressions of IL-10, TGF-β, Nrf2, SOD, Cu/Zn-SOD and GSH-Px were significantly down-regulated, while the relative expressions of NF-κB, TNF-α, IL-1β and IL-8 were significantly up-regulated (P < 0.05). Villus heights and crypt depths of proximal and mid intestine were significantly affected with dietary replacement of FM with PMM increasing 0 to 40% (P < 0.05). The structure of the intestinal microbial flora showed that the relative abundances of beneficial bacteria decreased, and the relative abundances of pathogenic bacteria increased in fish fed with P50 diet compared with the control group. In conclusion, replacing FM with PMM up to 30% had no significant impact on growth performance and feed utilization of golden pompano. However, 30% replacements of FM with PMM exerted adverse effects on antioxidant capacity and immune response of fish. In addition, replacement of a high proportion of FM with PMM negatively affect the gut microflora of fish.

Replacement of fishmeal with plant protein in the diets of juvenile lumpfish (Cyclopterus lumpus, L. 1758): Effects on digestive enzymes and microscopic structure of the digestive tract

This study investigated the effects of plant protein concentrates on the activity of digestive enzymes and microscopic structure of the intestine of juvenile lumpfish. The experiment was carried out using triplicate groups of lumpfish of 7 g average initial body weight, to 40 g average final weight, after 54 days. Four experimental diets were used; a fishmeal (FM) based control diet and three test diets with the plant protein concentrates; soy protein concentrate (SPC) and pea protein concentrate (PPC) (1:1 ratio) replacing FM in proportions of 25% (PP25), 50% (PP50) and 75% (PP75), respectively. Nested ANOVA showed several significant treatment differences in histomorphometry. Overall, fish fed test diets exhibited several changes such as shorter mucosal fold height (MFH) in the anterior intestine (AI), increased number of goblet cells (GCs) and width of lamina propria (WLP) in distal intestine (DI), compared to control. Principal component analysis (PCA) on histological indices showed that all three treatment groups (i.e. PP25, PP50 and PP75) had significantly altered overall intestinal architecture, compared to the control group. The observed enteritis was negatively related with the condition factor (CF). Regarding enzyme activities fewer changes were observed across diets. Fish fed the PP50 diet exhibited an increased activity of leucine aminopeptidase (LAP) in the pyloric caeca and a decrease on chymotrypsin (CHY) in the mid intestine (MI) compared to the control. Nevertheless, the overall changes captured by PCA on enzymes were associated only with condition factor (CF) and not with the diets. Overall, histological evaluation confirmed that lumpfish intestinal morphometry was significantly altered by plant protein ingredients at 25%, 50% and 75% levels, but replacing of FM up to 50% did not affected the growth and the enzyme activities up to 75% inclusion level.

Features of pathogenesis in sacbrood virus at honey bees (Apis mellifera L.)

Bees and their larvae are prone to various viral diseases, which lead to disruption of the vital activity of the bee colony and sometimes to its death. It is hazardous for the bee colony when a sac-like brood damages it. Sick families differ sharply from healthy ones in terms of their condition and productivity; they develop slowly in the spring and grow few offspring. Adult bees of sick families do not live long; they are not very active, weakly protect nests, fly sluggishly, and are unfriendly to collect honey. Therefore, the work aimed to identify physiological changes in the intestines of sexually mature ewes affected by cystic brood. The experimental part of the work was carried out in the conditions of the Stepan Gzhytskyi National University of Veterinary Medicine and Biotechnologies Lviv. The research was conducted during 2018–2020 at a farm in the Stryi district of the Lviv region. The farm's apiary consisted of 230 bee families. The subjects of the study were fertile uteri aged two years. Signs of virus damage were detected on the farm in 2018 and 2019. The diagnosis was confirmed based on epizootological data, clinical signs, and laboratory studies. By conducting histological studies, data on the pathogenesis of honey bees affected by the virus were supplemented. The data on physiological and morphological changes in the middle intestine of pregnant mothers are given. Histological studies were carried out in different parts of the mid intestine. Changes in the function of the peritrophic membrane were found in sick uteri compared to clinically healthy ones. An increase in the length of the midgut fold in the front part of the intestine by 23% was revealed (Р ˂ 0.001). Under the influence of the pathogenicity of the virus, there is an intensive proliferation of enterocytes in the middle part of the intestine. In the case of damage by a sac-like brood, the work of the membrane-associated with the motor, secretory and other functions of the midgut is disturbed. This, in turn, leads to dystrophic and inflammatory changes in the surface epithelium and also inhibits the regeneration process. Damage to the structural components of the mucous membrane is indicated by the absence of a hypertrophic membrane in the caudal direction of the midgut of sick mothers, where necrotic damage to the mucous membrane up to the basement membrane is revealed.

Effects of dietary galactooligosaccharide on growth, antioxidants, immunity, intestinal morphology and disease resistance against Aeromons hydrophila in juvenile hybrid sturgeon (Acipenser baerii♀ × A. schrenckii♂)

The present study investigated the effects of dietary galactooligosaccharide (GOS) supplementation on growth, antioxidant capacity, immunity, intestinal morphology and resistance to Aeromons hydrophila of hybrid sturgeon (Acipenser baerii♀ × A. schrenckii♂). A total number of 360 fish were randomly distributed into 12 aquaria and fed diets supplemented with GOS at 0%, 1%, 3% and 5% concentrations (designated as control, GOS1, GOS3 and GOS5) for 8 weeks. Then 30 fish from each group were intraperitoneally challenged with A. hydrophila, and mortality was recorded for the next 15 days. The results showed that there were significant differences of final body weight (FBW), weight gain (WG), specific growth rate (SGR) and feed conversion ratio (FCR) in sturgeon fed GOS diets. The lysozyme, ACP, AKP and MPO activities in sturgeon serum fed GOS diets were higher than those with control diet. Significant increase of SOD, CAT and GSH-PX capacity and remarkably decrease of MDA content were observed in liver of fish fed GOS diets. Remarkable enhancement of muscular thickness, villus and microvilli height, and goblet cells in mid intestine was observed in GOS supplemented groups. In spiral valve, supplementation of any quantities of GOS promoted an evident increase in the muscular thickness, villus height and goblet cells, while the villus width and crypt depth were relatively invariant. The IL-1β and IL-8 mRNA levels were decreased and TNF-α gene expression was increased by dietary GOS. The challenge test with A. hydrophila resulted in lower mortalities by GOS administration in a dose-dependent manner and the highest relative percent survival (36.67 ± 1.92%) was observed in fish fed GOS5 diet. The study concludes that GOS inclusion at the rate of 3% is recommended to increase the growth performance, antioxidant capability and immunity as well as regulate intestinal morphology and promote resistance against A. hydrophila in hybrid sturgeon.

Growth performance, plasma components, and intestinal barrier in grouper (Epinephelus coioides) are altered by dietary fish meal replacement with extruded soybean meal

An 8-week feeding trial was conducted to investigate whether extruded soybean meal (ESBM) replacing fish meal (FM) in the feed affect the growth performance, plasma components and intestinal barrier of Epinephelus coioides. Five isonitrogenous, isocaloric experimental diets were formulated using ESBM substitution for FM protein at incremental levels of 0, 15%, 30%, 45%, 60%. Each diet was randomly assigned to one of the five groups with triplicate tanks of 20 juvenile fish with an average initial weight of (52.97 ± 0.10) g, and hand-fed twice daily across the feeding trial. Weight gain rate, specific growth rate, feed efficiency, feed intake and the whole-body lipid had negative linear and/or quadratic responses to dietary ESBM inclusion levels. There are similar patterns for the plasma levels of HDL-C, LDL-C, TP, TC, TG, C3, and IgM, but the opposite trend was observed for plasma endotoxin and endothelin-1 levels. The trypsin activity in mid intestine (MI) and distal intestine (DI) and protease activity in DI showed negative linear and quadratic responses to increasing dietary ESBM inclusion levels. The muscle layer thickness of MI and the mucosal fold length and muscle layer thickness of DI showed negative linear and quadratic responses to increasing dietary ESBM inclusion levels. The mRNA levels for IL-8 in MI and DI, IL-10 in the three intestinal segments (proximal intestine (PI), MI, and DI), IL-1β, IL-12 and TNF-α in PI showed positive linear and/or quadratic responses to increasing dietary ESBM inclusion levels, whereas negative linear and/or quadratic responses were observed for TGF-β1 mRNA levels in MI and DI. The above results indicate that dietary ESBM inclusion at above 45% FM protein could reduce the growth performance and immunity of grouper by reducing intestinal digestive capacity and plasma lipid levels, as well as inducing inflammatory reactions.