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A feeding trial of eight weeks was conducted to examine the influence of food supplementation with lauric acid (LA) on Acanthopagrus schlegelii (juvenile black sea bream). A 24 percent fish meal baseline diet was created, while the other two diets were generated with dietary supplementation of graded points of LA at 0.1 percent and 0.8 percent, respectively. Each diet was given a triplicate tank with 20 fish weighing 6.22 ± 0.19 g. In comparison with the control group, the weight gain rate, growth rate, as well as feed efficiency of fish fed of 0.1 percent diet of LA were considerably (P < 0.05) greater. The total body and dorsal muscle proximate compositions did not change significantly between groups (P > 0.05). Triglyceride (TG) content was considerably (P < 0.05) greater in the LA-supplemented meals eating group in comparison with the control group. In the group eating LA-supplemented meals, the height of villus and the number of goblet cells/villus were considerably (P < 0.05) larger. The microbial makeup of the gut was also studied. The differences in phyla, class, and family level were not statistically significant (P > 0.05). Firmicutes in the phylum, Betaproteobacteri, Gammaproteobacteria, and Clostridia in the class, and Clostridiaceae in the family were all substantially increased with higher levels of LA supplementation (P < 0.05). According to the findings of this study, an LA-supplemented diet improves fish development, antioxidative capability, gut microbiota and intestinal health.

This study investigates the effects of three dietary additives—microencapsulated sodium butyrate (MSB), glycerol monolaurate (GML), and tributyrin (TB)—on the growth performance, various physiological parameters, gene expression, intestinal morphology, and microflora in Acanthopagrus schlegelii (black sea bream). The experiment utilized a 43.5% soybean meal (SBM) inclusion diet with four isonitrogenous and isoenergetic formulations: a control diet, and diets supplemented with MSB (0.24%), GML (0.04%), or TB (0.22%). The growth trial spanned eight weeks, and triplicate tanks were randomly assigned to each diet, with each tank containing 30 fish, each having an initial weight of 1.55 ± 0.01 g. Key outcomes included measurements of weight gain, specific growth rate, digestive enzyme activity, serum immune markers, antioxidant status, and intestinal morphology and, gut microbiota. Additionally, gene expression and microbiota analysis were conducted on intestinal tissues to assess the impact of these additives on gut health and immune response. The findings revealed that all three additives enhanced growth performance and improved intestinal health and gut microbiota but GML exhibited the most pronounced effects on intestinal barrier function and immune modulation, gene expression, and microflora, followed by MSB and TB. This study provides a comprehensive comparison of MSB, GML, and TB as feed additives for black sea bream, offering insights into their potential for improving fish health and optimizing aquaculture feed formulations.

Berberine, an isoquinoline alkaloid found in some traditional medicinal plants, such as Berberis vulgaris and Coptis Chinensis , has been considered as an effective drug in treating obesity, hypertension, type-2 diabetes, hyperlipidemia, and gout in humans and animals. It currently has certain applications in fish nutrition and health, mainly because it has strong biological and pharmacological properties, such as antioxidative, anti-inflammation, antidiarrheal, analgesic, antimicrobial, anticancer, hepatoprotective, and lipid- and glucose-lowering properties. Recent studies revealed that berberine supplementation in different fish diets could alleviate liver pathological changes, intestinal histological and microbiota alterations caused by high lipid and carbohydrate diets, as well as improve growth performance, antioxidative and immune status, and stress resistance ability of fish. However, the beneficial effects of berberine vary with fish species, basal diet, feeding modes, supplementation level, and etc. This review highlights the bioavailability and toxicity of berberine, and its mechanisms in lipid and glucose metabolism, antioxidation, anti-inflammation, and protection of intestinal health, as well as the other findings on supplementing berberine in the fish diet. Moreover, this review provides future perspectives on berberine application in fish nutrition and health.

Single-cell proteins are attracting growing attention as viable alternatives for fishmeal (FM) in aquatic feed. Methanotroph ( Methylococcus capsulatus , Bath) bacteria meal FeedKind ® (FK) is a type of single cell protein with high protein content (75.14%) and desirable amino acids profile, produced by Methylococcus capsulatus (Bath) living on methane consumption. The present study evaluated the potential of replacing FM with FK in the diet of black sea bream ( Acanthopagrus schlegelii ). Five iso-energetic and iso-nitrogenous diets were designed with FK replacing 0, 4.13, 8.27, 16.53, and 24.80% FM protein in the basal diet (40% FM content), respectively. All the diets were fed to three replicates of fish (initial weight 6.56 ± 0.02 g) for 70 days. After the feeding trial, replacing dietary 8.27% FM protein with FK significantly improved the weight gain and specific growth rate of fish ( P < 0.05), while other groups showed no significant difference in the growth performance ( P > 0.05). The fish fed diets with 8.27 and 16.53% replacement levels exhibited significantly increased feeding rates. The 8.27% FK diet significantly increased the whole-body and muscle crude protein contents, apparent digestibility of crude lipid, foregut, and midgut amylase activities. The microvillus density in the midgut of fish fed the 24.80% FK diet significantly increased. The diet with 8.27% FK increased the serum triglyceride content of the fish, while the 24.80% FK diet reduced the serum triglyceride, total cholesterol, and low-density lipoprotein cholesterol contents of the fish. In conclusion, the results indicated that replacing dietary FM protein with up to 24.80% FK had no adverse effects on the growth of black sea bream, whilst replacing 8.27% FM protein with FK enhanced its growth performance and feed utilization.

Exploring alternatives to fishmeal (FM) in aquaculture nutrition remains a hot topic in this area. Yarrowia lipolytica (YL), a promising single-cell protein source, has yet to be evaluated for its use on the Pacific white shrimp ( Litopenaeus vannamei ) diet. This investigation assessed the effects of YL on growth performance, metabolism, antioxidant capacity, and nutrient digestibility in shrimp. Seven diets with equal protein and lipid contents were prepared, incorporating gradient YL (dry matter basis): 0% (control), 1.50%, 3.00%, 4.50%, 6.00%, 9.00%, and 12.00%. During a 56-day feeding trial involving shrimp, with an initial average weight of 0.32 ± 0.02 g, each kind of diet was randomly assigned to six tanks. It was observed that the growth performance improved initially but then exhibited a declining trend as the dietary inclusion of YL increased. Regression analysis indicated 2.68% as the optimal YL percentage for a specific growth rate (SGR), accounting for 10.54% of the dietary FM content. A higher YL (over 6.00%), which is equivalent to replacing over 23.6% of the FM, led to increased feed intake and conversion ratios, possibly correlating with decreased YL digestibility. However, YL inclusion across the studied range had no detrimental impact on intestinal or hepatopancreatic morphology. Notably, higher YL levels significantly enhanced hepatopancreatic trypsin activity and reduced serum triglyceride and cholesterol levels. The inclusion of YL notably augmented antioxidant defense mechanisms in shrimp, as evidenced by increased total antioxidant capacity and catalase activities, as well as reduced malondialdehyde levels in the hepatopancreas, possibly due to the presence of β-glucan and mannan oligosaccharides in YL. These findings support YL being viable as a protein source in shrimp feeds.

Litopenaeus vannamei was divided into seven groups (defined as diets A0–A6) and fed with diets respectively containing 0, 0.5, 1, 2, 4 and 8 g/kg Yarrowia lipolytica (astaxanthin content: 1.5%) and 3 g/kg Haematococcus pluvialis (astaxanthin content: 2%). After an eight-week feeding trial, the results reflected that different levels of Y. lipolytica and H. pluvialis could significantly increase the weight gain rate of L. vannamei (p < 0.05). The condition factor and weight gain rate of group A4 were significantly higher than those of the other groups (p < 0.05); the HSI significantly decreased with the increase of Y. lipolytica (p < 0.05). The addition of Y. lipolytica to the diet had significant effects on total protein (TP), albumin (ALB), glutathione peroxidase (GSH-Px), malonaldehyde (MDA) and total antioxidant capacity (T-AOC) (p < 0.05). The total protein and albumin of the A5 and A6 groups were significantly higher than those of the other groups (p < 0.05). The GSH-Px activity of the A5 group was the highest and the T-AOC of the A0 group was the lowest. Inducible nitric oxide synthase (I-NOS) increased with the addition of Y. lipolytica (p < 0.05). Y. lipolytica inclusion had no negative effect on physiological and biochemical parameters and some serum immune and antioxidant indexes (p > 0.05). Astaxanthin in Y. lipolytica had an obvious effect on body color. After cooking, the body color of the shrimp deepened with increasing Y. lipolytica content. The red body color of L. vannamei was significantly improved by adding yeasts hydrolysate 2~8 g/kg to the diet. According to the regression analysis between the level of Y. lipolytica added to the diets and the weight gain rates, the optimal level of Y. lipolytica is 4.64 g/kg.

China is the largest food fish producer in the world. Chinese consumers normally purchase fish that are still alive to ensure freshness. Therefore, the live transport of fish is important in China’s aquaculture, although it carries potential risks for animal welfare. This study investigated the attitudes and knowledge of stakeholders within Chinese aquaculture towards the live transport and welfare of fish. Semi-structured interviews were conducted with 12 participants who were involved with the aquaculture industry in China. Most participants self-rated their transport-related knowledge as moderate and had some understanding of animal welfare, although this term was generally considered only relevant to terrestrial animals. Participants’ responses indicated that the live transport of fish occurs frequently in China, generally using sealed tanks, plastic bags, and foam boxes, in purpose-built vehicles. Seasonal changes, such as changes in ambient and water temperature, are considered to be important contributors to successful live transport, as well as sufficient oxygen supplies and stocking density. The use of anesthetics was not commonly reported, particularly in food fish, and fish capture is predominantly by conventional dipnets. The health status of transported fish is determined mostly by morphology (body injury, body or eye color, and fin condition), as well as vigor and swimming ability. Our results indicate that live transport poses a number of welfare risks to fish but that participants in the process associated welfare concerns more with terrestrial animals, not fish.

An eight-week feeding trial was conducted to examine the impact of dietary supplementation with glycerol monolaurate (GML) on juvenile black sea bream. A basal diet was formulated containing 24% fish meal, while five additional diets were prepared, each supplemented with varying levels of GML: GML1 (0.01%), GML2 (0.02%), GML3 (0.04%), GML4 (0.08%), and GML5 (0.16%). Triplicate tanks were randomly allocated to each diet, each containing 20 fish with an initial weight of 1.55 ± 0.05 g. By the trial’s end, the GML3 group displayed a notably higher final body weight (FBW), weight gain (WG), specific growth rate (SGR), and protein efficiency ratio (PER) compared to the other groups (p < 0.05), but the FCR was significantly higher in the control group. However, no significant differences were observed in the MFI, PPV, CF, HSI, IPF, VSI, or SR among the groups (p > 0.05). Regarding the proximate compositions of the dorsal muscle and whole body, no substantial differences were observed across the groups (p > 0.05). Additionally, there were no significant variations in digestive enzyme activity (p > 0.05), serum immune, or biochemical parameters in the midgut and hindgut among the treatment groups. But in the serum immune response IgM, C3 and C4 were significantly higher in the GML3 group as compared to the other groups (p < 0.05). However, the GML3 group exhibited significantly greater fore-intestinal villus height, crypt depth, villus height per crypt depth, and the number of goblet cells per villus compared to the other groups (p < 0.05). Overall, GML supplementation, particularly GML3, significantly improved growth indicators like the final body weight and intestinal morphology. While certain parameters remained unaffected, these findings suggest GML’s potential as a beneficial dietary supplement in fish diets.

The present study aimed to investigate the macroscopic and histological structure of the gastrointestinal tract (GIT) of Larimichthyscrocea (Richardson, 1846). It consists of esophagus, stomach regions, pyloric caeca, intestinal regions, and rectum. Sixteen tubular light yellowish pyloric caeca of similar sizes were observed in all individuals. The digestive wall consists of mucosa, submucosa, muscularis, and adventitia. No major differences appeared in the structure of the tunica, epithelial cell types, connective tissues and musculature glands of L.crocea GIT. The mucosal epithelia in the oesophagus has longitudinal branched folds with frontward and hindmost zones. The gastric tunica mucosa has a characteristic folded structure and can be divided into three regions. The intestinal tunica mucosa is characterized by villi structures and numerous mucus-secreting cells. Mucus-secreting goblet cells were strongly positive to AB at pH 2.5 in the oesophagus (excluding gastro-oesophageal junction) and intestine mucosal regions, which indicates an abundance of carboxylate mucins. The surface epithelia of the gastric mucosa is PAS-positive and AB-negative. SEM examination revealed that cells in the epithelium of the esophagus have an unbroken apical layer and goblet cells. The intestinal coefficient (IC) of L.crocea was 0.80 ± 0.21, consistent with a carnivorous or omnivorous habit. Our study adds the knowledge of the digestive system of L.crocea and might be useful in the management of L.crocea stocks.

Acidification (OA), a global threat to the world’s oceans, is projected to significantly grow if CO2 continues to be emitted into the atmosphere at high levels. This will result in a slight decrease in pH. Since the latter is a logarithmic scale of acidity, the higher acidic seawater is expected to have a tremendous impact on marine living resources in the long-term. An 8-week laboratory experiment was designed to assess the impact of the projected pH in 2100 and beyond on fish survival, health, growth, and fish meat quality. Two projected scenarios were simulated with the control treatment, in triplicates. The control treatment had a pH of 8.10, corresponding to a pCO2 of 321.37 ± 11.48 µatm. The two projected scenarios, named Predict_A and Predict_B, had pH values of 7.80-pCO2 = 749.12 ± 27.03 and 7.40-pCO2 = 321.37 ± 11.48 µatm, respectively. The experiment was preceded by 2 weeks of acclimation. After the acclimation, 20 juvenile black sea breams (Acanthopagrus schlegelii) of 2.72 ± 0.01 g were used per tank. This species has been selected mainly due to its very high resistance to diseases and environmental changes, assuming that a weaker fish resistance will also be susceptibly affected. In all tanks, the fish were fed with the same commercial diet. The seawater’s physicochemical parameters were measured daily. Fish samples were subjected to physiological, histological, and biochemical analyses. Fish growth, feeding efficiency, protein efficiency ratio, and crude protein content were significantly decreased with a lower pH. Scanning electron microscopy revealed multiple atrophies of microvilli throughout the small intestine’s brush border in samples from Predict_A and Predict_B. This significantly reduced nutrient absorption, resulting in significantly lower feed efficiency, lower fish growth, and lower meat quality. As a result of an elevated pCO2 in seawater, the fish eat more than normal but grow less than normal. Liver observation showed blood congestion, hemorrhage, necrosis, vacuolation of hepatocytes, and an increased number of Kupffer cells, which characterize liver damage. Transmission electron microscopy revealed an elongated and angular shape of the mitochondrion in the liver cell, with an abundance of peroxisomes, symptomatic of metabolic acidosis.