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This experiment aimed to evaluate the impact of dietary hydroxyproline (Hyp) supplementation on the muscle quality of juvenile Pacific white shrimp (Litopenaeus vannamei) fed a low fishmeal diet. Six formulated diets included one high fishmeal (HF; 25% fishmeal content) and five low fishmeal diets (10% fishmeal content) with 0%, 0.2%, 0.4%, 0.6% and 0.8% Hyp (LF0, LF2, LF4, LF6 and LF8, respectively). Each diet was assigned to four replicates, and 40 shrimp (0.32 ± 0.00 g) per replicate were fed four times a day for 8 weeks. Dietary Hyp supplementation had little effects on growth performance, but increased the contents of Hyp, prolyl 4-hydroxylases (P4Hs), and collagen. The meat yield, springiness, hardness, chewiness, and cohesiveness of muscle were the highest in the LF4 group among the low fishmeal groups (P < 0.05). Cooking loss and freezing loss of muscle were the lowest in the LF4 group (P

This research examined the impacts of varying silybin dosages in high-lipid diets on the growth, hepatic histology, immunity, and immune-related gene expression of juvenile hybrid grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂). The grouper (with an initial body weight of 8.27 ± 0.08 g) were fed diets containing silybin at levels of 0 g/kg (S1, control group), 0.05 g/kg (S2), 0.10 g/kg (S3), 0.15 g/kg (S4), 0.20 g/kg (S5), 0.25 g/kg (S6), and 0.50 g/kg (S7) for 8 weeks. The study results suggest that the silybin-treated groups displayed an initial increase followed by a decrease in final body weight and specific growth rate, with the highest value observed in the group S5. In serum samples, silybin supplementation of high-lipid diets resulted in increased activities of alkaline phosphatase (AKP), superoxide dismutase (SOD) and catalase (CAT) enzymes, decreased activities of aspartate transaminase (AST) and alanine transaminase (ALT) enzymes and increased total antioxidant capacity (T-AOC) content. In liver, the addition of silybin to high-lipid diets increased SOD, CAT, and lysozyme (LYZ) enzyme activities, increased T-AOC and immunoglobulin M (IgM) contents, and decreased reactive oxygen species (ROS) and malondialdehyde (MDA) contents. Contrasted with the control group, the addition of silybin at 0.05–0.50 g/kg enhanced the hepatic histomorphology, for example, ameliorating the indistinctness of cell outlines and diminishing the hepatocyte vacuolation. Silybin treatment significantly upregulated the expression of liver sod, cat, gpx, nrf2, keap1, hsp70, hsp90, tlr22, myd88, il-1β, tnf-α and il-6(P < 0.05). Silybin treatment significantly upregulated the expression of tlr22, myd88, il-1β, tnf-α, and il-6 of head kidney (P < 0.05). After vibrio harveyi challenge, groups S5-S6 showed higher survival than the control. Incorporating silybin into high-lipid diets boosts grouper's growth, antioxidant, and immune abilities. Regression analysis implies adding 0.23 g/kg silybin to the diets of juvenile hybrid grouper.

This research was performed to assess the possibility of substituting fishmeal (FM) with wheat gluten meal (WGM) at different levels. WGM in the total diet (%) are as follows; W0 (0%), W10 (10.21%), W12 (12.42%), W14 (14.65%), W16 (16.87%), and W19 (19.1%) as well as its effects on growth, and immunity in juvenile pearl gentian groupers (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂). A sum of 540 healthy fish (average initial body weight 11.04 ± 0.02 g) was selected randomly and put in eighteen fibreglass tanks (0.3 m3) (six groups with three replicate) at a density of 30 fish per tank and fed with experimental diets twice daily at 08:00 and 16:00 to apparent satiation for eight weeks. WGM102 had a significantly higher weight gain rate (498.82±22.50%) than the control group (345.57±24.93%) (P

An 8-week feeding trial was conducted to assess the impact of replacing fish meal (FM) with rubber seed cake (RSC) on growth performance, digestive enzyme activity of the gut, antioxidant capacity and protein metabolism-related parameters of plasma and liver in juvenile Asian red-tailed catfish (Hemibagrus wyckioides) with an average body weight of 3.21 g. Four isonitrogenous (41.08 ± 0.17) and isolipidic (10.07 ± 0.11) diets were formulated, incorporating RSC at a level of 0%, 15%, 30%, and 45% (w/w) to progressively replace FM. Dietary inclusion of 15–30% RSC did not significantly affect growth performance (p > 0.05). However, the replacement of FM with RSC resulted in linear reductions in intestinal trypsin and amylase activities, with a significant reduction in intestinal amylase activity observed at the 45% RSC inclusion level. Dietary inclusion of 30–45% RSC decreased plasma glutamate dehydrogenase and aspartate aminotransferase activities, but increased plasma adenosine monophosphate deaminase and hepatic γ-glutamyltransferase activities. This may indicate that the high substitution of FM by RSC may affect the homeostasis of amino acid metabolism. Dietary inclusion of 15% RSC did not affect serum and hepatic antioxidant enzyme activities; however, dietary inclusion of 45% RSC significantly increased plasma malondialdehyde level, but decreased catalase activity. Furthermore, dietary inclusion of 30–45% RSC significantly increased hepatic lactate dehydrogenase activity. These results demonstrated that replacing a portion of FM with RSC is feasible, and dietary inclusion of 15% RSC did not have significant adverse effects on growth performance, digestive function and antioxidant capacity of H. wyckioides.

Several reports have revealed the vital role that probiotics play in fish growth and health. However, few works are available for host gut-derived probiotics on the growth, immunity, and gut microbiota of fish, especially in hybrid grouper (♀Epinephelus fuscoguttatus × ♂Epinephelus lanceolatus) due to their isolation difficulty and functional verification. This study aimed at assessing 3 host gut-derived Bacillus species' effects on the growth, immune and antioxidant-biochemical responses, haematological parameters, intestinal morphology, immune-related gene expression, gut microbiota, and disease resistance against Vibrio harveyi in hybrid grouper. A total of 480 hybrid grouper (initial weight = 9.03 ± 0.02 g) were randomly allotted into 4 groups, namely, the group fed a basal diet without probiotic inclusion (control, B0), the group fed the basal diet with Bacillus velezensis GPSAK4 (BV), the group fed the basal diet with Bacillus subtilis GPSAK9 (BS), and the group fed the basal diet with Bacillus tequilensis GPSAK2 (BT) strains at 1.0 × 109 CFU/g. After a 6-week feeding trial, the results revealed significant improvements (P

This study was conducted to evaluate the influence of dietary lysophospholipids combined with 1% dietary fish oil reduction on the growth performance and hepatic lipid metabolism of largemouth bass (Micropterus salmoides). Five isonitrogenous feeds were prepared with lysophospholipids at 0% (fish oil group, FO), 0.05% (L-0.05), 0.1% (L-0.1), 0.15% (L-0.15) and 0.2% (L-0.2), respectively. The dietary lipid was 11% in the FO diet and 10% in the other diets. Largemouth bass were fed for 68 d (initial body weight = 6.04 ± 0.01 g) with 4 replicates per group and 30 fish per replicate. The results showed that the fish fed diet containing 0.1% lysophospholipids had higher digestive enzyme activity and obtained better growth performance compared to the fish fed FO diet (P

This study investigated the effect of adding the compound acidifiers on the intestine health of hybrid grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂) fed diet with higher cottonseed protein concentrate (CPC). To assess the benefits of compound acidifiers helping CPC to replace more fish meal (FM) for hybrid grouper, five isonitrogen and isolipid experimental diets were formulated. The five diets consisted of a control diet (FM, 50%) and four experimental diets (27.5% FM, 27.27% CPC), each of which contained compound acidifiers to varying degrees (FCA0, FCA0.05, FCA0.1, and FCA0.2). Each diet was fed to three replicates of each group for 8 weeks. In the FCA0.05 group, the results demonstrated a statistically significant increase in protein efficiency ratio, lipid efficiency ratio, and the activity of digestive enzymes in the intestine (P

This study aimed to investigate the potential of replacing soybean meal (SBM) with corn gluten meal (CGM) in the diet of Pacific white shrimp (Litopaeneaus vannamei). The study examined the effects of a dietary soybean meal replacement on growth, biochemical indices, antioxidant activities, histology, and intestinal flora. A total of 840 juvenile Pacific shrimp were fed seven diets containing different levels of CGM, ranging from diet 1 (diet1) 0% (control), diet2 (3%), diet3 (7%), diet4 (9%), diet5 (11.8%), diet6 (12.7%), and diet 7 (14.4%). The experiment was conducted over 56 days, with three replicate of each group (initial mean weight = 0.13 0.00 g). The results showed that dietary CGM significantly increased final body weight, average weight gain, and specific growth rate. However, the inclusion of dietary CGM decreased with higher levels. The feed conversion ratio of diets 2 and 3 was considerably lower than that of the control group. The activities of alkaline phosphatase and acid phosphatase increased significantly with the feeding of CGM, while the levels of alanine aminotransferase and aspartate aminotransferase decreased significantly. The histology of the hepatopancreas showed an evident epithelial tubule (E, B, R, and F), and the number of intact epithelial cells increased considerably with the increasing inclusion of CGM (P

Seven diets were formulated to investigate the effects of glutathione-rich yeast hydrolysate (GYH) on growth performance, antioxidant capacity, and innate immunity of Litopenaeus vannamei. Based on the control diet (28% fishmeal content, CON), six diets supplement with GYH 0% (G0), 0.3% (G0.3), 0.5% (G0.5), 0.7% (G0.7), 0.9% (G0.9) and 1.1% (G1.1) were prepared after cottonseed protein concentrate replacing fishmeal 28.5% of the CON. After the 8 weeks feeding experiment, the shrimp fed diet containing 0.5%− 0.9% GYH obtained better growth performance compared to the CON and G0 groups, as well as the significantly lower feed conversion rate (P

With global warming, high water temperature events are becoming more frequent in summer. The liver of the largemouth bass (Micropterus salmoides) is particularly sensitive to heat stress, especially in the rapid growth period with high nutrient concentration. In this experiment, a metabolomic analysis was conducted to reveal how steroidal saponins alleviated high temperature stress in largemouth bass. Fish were divided into three groups, two groups fed the basic diet, the third group fed the experimental diet contained steroidal saponins. After the fish ingested the diets for four weeks, the heat temperature stress test began. The first group fed basic diet without the heat stress (C), and the second group fed basic diet with the heat stress (H), and the third group fed experimental diet containing steroidal saponins with heat stress (HS). After 1-week of heat stress, metabolic analysis showed that high temperature stress mainly affected phospholipid metabolism, fatty acid metabolism, glutathione metabolism and bile metabolism in the fish livers of H group. The expression of genes glutathione peroxidase and heme oxygenase-1 were decreased and the nuclear factor kappa-B activated inflammation in fish feeding in group H. The adenosine 5′-monophosphate-activated protein kinase pathway was activated in the HS group. Compare to the fish in H group, those metabolism observed in fish in HS group were greatly improved, similar to the C group. Thus, steroidal saponins could help relieve the liver burden when largemouth bass facing heat stress in summer.

Due to diminishing fish meal (FM) supplies, superb protein (PRO) sources are needed for aquaculture, such as soy-based PRO. However, these can cause enteritis and even intestinal injury in fish when used at high proportions in feed. This research examines the effects of substituting soybean protein concentrate (SPC) for FM on the growth performance and intestinal balance of pearl gentian groupers and investigates the mechanism of SPC-induced enteritis. Experimental fish (n = 720) were fed 1 of 3 following diets: (1) a 50% FM diet (control), (2) a diet with 20% of the FM substituted with SPC (group SPC20), and (3) a 40% SPC-substituted diet (SPC40). Fish were fed for 10 wk iso-nitrogenous (50% PRO) and iso-lipidic (10% lipid) diets. Groups SPC20 and SPC40 showed significantly lower developmental performance and intestinal structures than control. Group SPC40 had significantly higher expressions of pro-inflammatory-related genes, such as interleukin 1β (IL1β), IL12, IL17 and tumor necrosis factor α and significantly lower expressions of anti-inflammatory-related genes, such as IL5, IL10 and transforming growth factor β1. Biochemical and 16S high-throughput sequencing showed that the abundance and functions of intestinal flora in group SPC40 were significantly affected (P

Glutamine has been used to improve intestinal development and immunity in fish. We previously found that dietary glutamine enhances growth and alleviates enteritis in juvenile hybrid groupers (Epinephelus fuscoguttatus♀ × Epinephelus lanceolatus♂). This study aimed to further reveal the protective role of glutamine on glycinin-induced enteritis by integrating transcriptome, proteome, and microRNA analyses. Three isonitrogenous and isolipidic trial diets were formulated: a diet containing 10% glycinin (11S group), 10% glycinin diet supplemented with 2% alanine-glutamine (Gln group), and a diet containing neither glycinin nor alanine-glutamine (fishmeal, FM group). Each experimental diet was fed to triplicate hybrid grouper groups for 8 weeks. The analysis of intestinal transcriptomic and proteomics revealed a total of 570 differentially expressed genes (DEGs) and 169 differentially expressed proteins (DEPs) in the 11S and FM comparison group. Similarly, a total of 626 DEGs and 165 DEPs were identified in the Gln and 11S comparison group. Integration of transcriptome and proteome showed that 117 DEGs showed consistent expression patterns at both the transcriptional and translational levels in the Gln and 11S comparison group. These DEGs showed significant enrichment in pathways associated with intestinal epithelial barrier function, such as extracellular matrix (ECM)-receptor interaction, tight junction, and cell adhesion molecules (P < 0.05). Further, the expression levels of genes (myosin-11, cortactin, tenascin, major histocompatibility complex class I and II) related to these pathways above were significantly upregulated at both the transcriptional and translational levels (P < 0.05). The microRNA results showed that the expression levels of miR-212 (target genes colla1 and colla2) and miR-18a-5p (target gene colla1) in fish fed Gln group were significantly lower compared to the 11S group fish (P < 0.05). In conclusion, ECM-receptor interaction, tight junction, and cell adhesion molecules pathways play a key role in glutamine alleviation of hybrid grouper enteritis induced by high-dose glycinin, in which miRNAs and target mRNAs/proteins participated cooperatively. Our findings provide valuable insights into the RNAs and protein profiles, contributing to a deeper understanding of the underlying mechanism for fish enteritis.

The utilization efficiency of soy protein is affected by its 2 anti-nutritional substances—the antigens β-conglycinin and glycinin. This study investigated their effects on the growth performance, intestinal immune defense, and microbiome in juvenile pearl gentian groupers (Epinephelus fuscoguttatus♀ × Epinephelus lanceolatus♂). Three isonitrogenous and isolipidic diets were formulated containing fishmeal supplemented with 70 g/kg β-conglycinin or 100 g/kg glycinin, or no supplementation (control). Each experimental diet was fed to quadruplicate groups with 30 fish in each tank for 8 weeks. Dietary inclusion of either β-conglycinin or glycinin significantly reduced weight gain and specific growth rates, and cell proliferation of the distal intestine. Histological evaluation of the intestine tract revealed the inflammation signs, characterized by reducing of plica height and width as well as the number of the goblet cells, and widening of the lamina propria. The group fed the β-conglycinin diet had reduced lysozyme activity, contents of immunoglobulin M and complements 3 and 4. Increased activities of caspase-3 and -9 were observed in the group fed the β-conglycinin diet compared to the other 2 groups. In the intestinal microbiota, the relative abundances of the potentially pathogenic genera Photobacterium and Vibrio were significantly higher in the glycinin group than those in others. Therefore, the existence of soybean antigens (β-conglycinin or glycinin) could damage the structural integrity of the intestine, reduce immune defense, reshape the intestinal microbiome and, ultimately, impair growth in fish.

This experiment was conducted to assess the possibility of replacing fishmeal (FM, Fishmeal content of the control group: 30%) with corn gluten meal (CGM) at the following levels: 0, 10, 20, 30, 40, and 60%. The experimental diets, formulated to be isonitrogenous and isocaloric, were studied for their effects on growth, feed utilization, digestive enzyme activity and apparent nutrient digestibility in juvenile white shrimps, Litopenaeus vannamei (initial mean weight = 0.71 ± 0.01 g). Seven hundred twenty healthy and uniformed-size shrimp were distributed to six groups of three replicates, each with 40 shrimp in each tank (0.5 m3). Each experimental diet was fed to shrimp four times daily to apparent satiation at 7:00, 11:30, 17:00, and 21:30, respectively, for 8 weeks. At the end of the experiment, the total weight of fish in each tank was weighed and randomly selected for testing, including fish nutrient composition and digestive enzyme activity. Results showed that no significant differences were observed in the weight gain rate (WGR), feed coefficient rate (FCR) and specific growth rate (SGR) of shrimp after 30% FM was replaced with CGM (P > 0.05), but these indicators significantly decreased at higher replacement rates. As CGM content increased, the content of crude protein and phosphorus in the shrimp decreased significantly (P < 0.05), whereas the crude fat content first increased significantly and then decreased (P < 0.05). Compared to the control group, the protease activity was significantly lower in the 40% group and the lipase activity was significantly lower in the 60% group (P < 0.05). Amylase activity was significantly increased with increasing CGM levels (P < 0.05). The digestibility of protein and lipid was significantly reduced by CGM replacement of more than 30% FM (P < 0.05). As CGM content increased, the digestion of energy and dry matter was first significantly increased and then significantly decreased (P < 0.05). In the 30, 40, and 60% groups, the digestibility of all amino acids (AA), except methionine (Met), arginine (Arg) and serine (Ser), was significantly lower than in the control group (P < 0.05). In summary, FM could be partially replaced by CGM in the feed of L. vannamei. Based on the broken-line regression analysis of WGR, the optimal dietary CGM replacement was 27.47%.

The effects of increasing dietary inclusion levels of L-carnitine at 0 (control group) 200, 400, 600, 1200, 1400, and 1600 mg/kg were evaluated in juvenile hybrid groupers exposed to heat shock stress. The feeding trial was conducted for eight weeks. After the feeding trial, hybrid groupers were subjected to a heat stress test for an hour at a temperature of 36 °C to determine the influence of the treatments on survival, biochemical parameters, and gene expression. The results of the current study showed that the survival rate of hybrid grouper was low in fish fed the control diet. A large number of survivors were observed in the treatment group with 400 mg/kg L-carnitine supplementation (LC 400), obtaining the highest survival rate. Heat stress decreased (P

This study was conducted to evaluate the effects of animal by-products on growth, digestive enzymes, disease resistance, hepatopancreas, and intestinal histological outcomes in Litopenaeus vannamei. Shrimp (initial weight [g] = 0.29 ± 0.01) were fed with four types of diets for 8 weeks: control diet supplemented with 8% fish meal (FM) and three diets containing 3% FM supplemented with 5% hydrolyzed porcine mucosa (HPM), yellow mealworm meal (YMM), or enzymatic chicken liver powder (ECLM). Results showed that HPM significantly increased the weight gain and specific growth rates of shrimp (P 0.05). Muscle crude protein content significantly increased in the HPM and ECLM groups and significantly decreased in the YMM group (P

This study aimed to evaluate the replacement of fishmeal with soybean and cottonseed protein concentrates and dietary supplementation of bile acids on the growth performance, immunity, molting, and intestinal health of Litopenaeus vannamei. Six diets were formulated: high fishmeal diet (HFM, 25% fishmeal), low fishmeal diet (LFM, 10% fishmeal), LBA1 (LFM + 0.15 g kg−1 bile acids), LBA2 (LFM + 0.3 g kg−1 bile acids), LBA3 (LFM + 0.6 g kg−1 bile acids), and LBA4 (LFM + 0.9 g kg−1 bile acids). Each diet was randomly assigned to triplicate groups of 40 shrimp (initial mean weight: 0.25 ± 0.00 g) per tank. After 50 d of the feeding trial, the final body weight significantly increased in shrimp fed the LBA4 diet compares to those fed the LFM diet (p

Hybrid grouper (♀Epinephelus fuscoguttatus × ♂Epinephelus lanceolatu) is a popular aquaculture species in recent years. The latest research has found that cottonseed protein concentrate (CPC) has been found to be an effective alternative to fishmeal in feed production, but high substitution rates could cause growth inhibition and organism damage in hybrid grouper. Compound acidifiers in previous studies could effectively enhance the growth and digestive performance of fish. Therefore, five isonitrogenous (50% crude protein) and isolipid (10% ether extract) diets were used: a reference diet (FM, 50% fishmeal) and four experimental diets (27.5% fishmeal, 27.27% CPC) containing acidifiers at 0%, 0.05%, 0.1%, and 0.2%, respectively. There were three replicates of 30 groupers per group and the experiment lasted for 8 weeks. The results showed a significant increase in WGR and SGR and a significant decrease in FCR with the addition of 0.05% acidifier (P

Iso-nitrogenous and iso-lipidic diets containing 0%, 3%, 6%, 9%, and 12% hydrolyzed porcine mucosa (namely, HPM0, HPM3, HPM6, HPM9, and HPM12) were prepared to evaluate their effects on the growth performance, muscle nutrition composition, texture property, and gene expression related to muscle growth of hybrid groupers (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂). Groupers were fed to apparent satiation at 08:00 and 16:00 every day for a total of 56 days. It was found that the weight gain percentage in the HPM0, HPM3, and HPM6 groups did not differ (P > 0.05). The cooking loss and drip loss of the dorsal muscle in the HPM3 group were lower than those in the HPM6 and HPM9 groups (P

An analysis of the extent of the effect of steroidal saponin addition on glucose and lipid metabolism in hybrid grouper liver was performed at the transcriptomic and metabolomic levels. Feeds (52% crude protein, 14% crude lipid) were prepared containing 0% (S0), 0.1% (S0.1), and 0.2% (S0.2) steroidal saponins. After eight weeks of feeding trial, compared to the S0 group, the activities of serum albumin, alanine aminotransferase, and aspartate transaminase were significantly lower and the activities of lysozyme, acid phosphatase, and alkaline phosphatase were significantly higher in the S0.1 group (p < 0.05). The superoxide dismutase, catalase, and glutathione peroxidase activities in the livers of the S0.1 group were significantly higher than those of the S0 group, while the malondialdehyde content was significantly lower than that of the S0 group (p < 0.05). There were forty-two differentially expressed genes and thirty-two differential metabolites associated with glucose and lipid metabolism enriched using KEGG and GO. In the S0 group, the expression of prostaglandin-endoperoxide synthase 1, prostaglandin E synthase 1, and thromboxane-2 synthase mRNA was significantly higher than in the S0.1 group (p < 0.05). The expression levels of genes in the S0 group were significantly higher than those in the S0.1 group (p < 0.05), including for glycogen synthase kinase, glucose-6-phosphatase catalytic subunit 2, fructose-1,6-bisphosphatase, phosphoenolpyruvate carboxykinase, glucose transporter 4, and malate dehydrogenase. The expression of mRNA such as fatty acid synthase, acetyl-CoA carboxylase, and sterol regulatory element-binding protein 1 was significantly lower in the S0.1 group than in the S0 group, while the expression of carnitine acyltransferase 1, acyl-CoA synthetase, and acyl-CoA dehydrogenase genes was significantly higher in the S0 group (p < 0.05). In summary, glycogen synthesis, gluconeogenesis, and the arachidonic acid metabolism pathway were inhibited by 0.1% steroidal saponins, and glycogenolysis, glycolysis, the tricarboxylic acid cycle, and the fatty acid β-oxidation pathway were activated. This study aims to provide a reference for the formulation of grouper feeds with a higher crude-lipid level.

Levels of dietary carbohydrates and lipids have important effects on the growth, health, and glycolipid metabolizing capacity of the hybrid grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂). This experiment evaluated the effect of carbohydrate to lipid ratios (CHO:L ratio) on growth, serum biochemical indices, intestinal morphology and activity of digestive enzymes, and the ability to metabolize carbohydrates and lipids in the hybrid grouper. Six iso-nitrogenous (500 g/kg) and iso-energetic (190 MJ/kg) feeds with CHO:L ratios of 0.82, 1.03, 1.28, 1.58, 1.94, and 2.27 were formulated. The 720 groupers with an initial body weight of 7.76 ± 0.08 g were sorted into 24 fiberglass buckets of 30 fish each. Feed was delivered twice daily at 8:00 and 16:00 to apparent satiety for 56 days. The results showed that the growth performance of the groupers was not significantly affected by the diet. Based on the specific growth rate (SGR), the optimal CHO:L ratio was 1.72 for the groupers by the second-order polynomial regression model. The intestinal trypsin and lipase, and the hepatic trypsin activities of the groupers showed a maximum in the 1.58 group. The intestinal muscle thickness in the 1.94 group and the villus length in the 1.58 group were significantly greater than in the 0.82, 1.03, 1.28, and 2.27 groups. The glycogen synthase, pyruvate kinase, and hexokinase activities of the liver were significantly higher in the 1.58 group than in the 0.82 and 2.27 groups. The hormone-sensitive triglyceride lipase, adipose triglyceride lipase, acetyl-CoA carboxylase, and carnitine palmitoyl transferase of the liver showed significantly higher activities in the 1.58 group than those in the 0.82 and 1.03 groups. These results showed that based on the SGR of the groupers, the best CHO:L ratio was 1.72. An appropriate dietary CHO:L ratio can reduce the lipid deposition of the fish body, liver, and muscle, as well as improve the intestinal morphology and activities of liver carbohydrate and lipid metabolism enzymes.

To study the dietary prebiotic role of Sulfate-Based alginate polysaccharide (SAP) in cottonseed protein concentrate-based diets, six iso-nitrogenous and iso-lipid feeds were prepared to feed grouper, including a fishmeal control group (FM) was set at 50% fishmeal level, on this basis 5 groups replacing 50% fishmeal protein with cottonseed protein concentrate and supplementing sulfate-based alginate polysaccharide 0%, 1%, 2%, 3% and 4% (SAP0, SAP1, SAP2, SAP3 and SAP4 groups). The healthy and vigorous grouper (initial weight = 8.63 ± 0.01 g) were selected and randomly divided into 6 treatment groups in triplicates (30 fish in each repetition). The feeding experiment was conducted for 8 weeks, followed by a one-week Vibrio harveyi challenge. The experimental results showed that the weight gain and specific growth rate reached the significant maximums in SAP2 and SAP3 groups (P

Dietary Clostridium autoethanogenum protein (CAP) has the potential to replace fishmeal (FM), but excessive CAP substitutions will affect gut health. Bile acids (BAs) have multiple benefits, but little information is available on the effects of BAs on Pacific white shrimp (Litopenaeus vannamei) fed a CAP diet (CAP replacing FM). An 8-week feeding trial were used to investigate the impacts of CAP substitution and BAs addition on structural changes of intestine, apoptosis, inflammatory cytokine and NFκB pathway of intestine, and transcriptomic profiles of hepatopancreas in Pacific white shrimp. Compared to PC (control) treatment, the NC (CAP50, CAP replacing 50% FM) treatment significantly decreased the fold height (FH) and villus length (VL) of midgut, and impaired the mitochondrial cristae. Compared to NC group, the FH was increased in BA1 (CAP50 with 0.03% BAs) and BA2 (CAP50 with 0.06% BAs) groups, the muscle layer thickness (MT) was decreased in BA2 and BA3 (CAP50 with 0.09% BAs) groups, the VL was increased in BA1 group, and the mitochondrial cristae was normal and well-defined in BA1 and BA2 groups (all p

Clostridium autoethanogenum protein (CAP) is an economical and alternative protein source. Here, three experimental diets were formulated with CAP replacing 0% (CAP-0), 30% (CAP-30), and 60% (CAP-60) of fishmeal to investigate the alterations of structure integrity, fatty acids profiles, and lipid metabolism in the muscle of pearl gentian grouper. With increasing levels of CAP substitution, the percentages of 16 : 0 or 18 : 0 were decreased in triglycerides (TG) and diacylglycerols (DG); 18 : 1 or 18 : 2 was increased at the sn−1 and sn−2 positions in phosphatidylethanolamines; 20 : 5n−3 was increased in TG and DG. The phosphatidylcholines (PC) (18 : 3/20 : 5), PC(22 : 6/17 : 1), and sphingomyelins (d19 : 0/24 : 4) were identified as potential lipid biomarkers between CAP treatments. The CAP-30 treatment enhanced lipolysis and lipogenesis, while the CAP-60 treatment inhibited lipogenesis. In conclusion, fishmeal replacement with CAP affected the lipid characteristics and lipid metabolism, whereas it did not affect the structural integrity and fatty acids profiles in the muscle of pearl gentian grouper.

An 8-week feeding trial was conducted to investigate the effects of C. butyricum on the growth performance, microbiota, immunity response, and disease resistance in hybrid grouper fed with cottonseed protein concentrate (CPC) replacement of fishmeal. Six groups of isonitrogenous and isolipid diets were formulated including a positive control group (50% fishmeal, PC), a negative control group (CPC replaced 50% of fishmeal protein, NC), and Clostridium butyricum supplemented with 0.05% (C1, 5×108 CFU/kg), 0.2% (C2, 2×109 CFU/kg), 0.8% (C3, 8×109 CFU/kg), and 3.2% (C4, 3.2×1010 CFU/kg), respectively, to the NC group. The results showed that weight gain rate and specific growth rate were significantly higher in the C4 group than that in the NC group (P

The substitution of high-level soy meals for fish meal (FM) generally leads to fish enteritis, accompanied by significant variations in gut flora. Relevant studies have pointed out a close relationship between tryptophan metabolism mediated by gut flora and vertebrate inflammatory bowel disease. Present study examines the role of tryptophan metabolism and gut flora profile in fish enteritis caused by different soybean meals. The 960 groupers were randomly assigned into 4 groups (n = 4), which including: (1) FM (the control group, fed with 50% FM feed), (2) SBM40 (replacing 40% FM with soybean meal), (3) SPC40 (replacing 40% FM with soybean protein concentrate), and (4) FSBM40 (replacing 40% FM with fermented soybean meal). Under average temperature and natural light, the groupers were cultivated with feeds of iso-nitrogen and iso-lipid for 10 weeks. The results showed that soybean meal feeds at all experimental levels had negative effects on fish gut physiology and growth performance. Typical enteritis features and fluctuations of immune system occur, which can be observed in the enzyme activities of total superoxide dismutase and lysozyme and in the contents of immunoglobulin M, complement 3 and complement 4. 16SrDNA high-throughput sequencing indicated that it greatly influenced the gut flora with the abundance of maleficent bacteria, like Vibrio, amplified with increasing dietary soybean meals. According to the “3 + 2” full-length transcriptome sequencing, soy meals at the three experimental levels inhibited the key gene expressions of tryptophan metabolic pathway in fish gut, however, there are some differences in the types of key genes that are inhibited. The canonical correlation analysis showed that the changes in key gene expressions in tryptophan metabolic pathway had a positive correlation with the expressions of pro-inflammatory genes (P < 0.05) and negatively correlated with the expression of anti-inflammatory genes (P < 0.05). It is speculated from this study that tryptophan metabolism is closely related to fish soy meal-related enteritis, and the abnormal tryptophan metabolism caused by intestinal flora imbalance may play an important role. In the future research, we can further study the tolerance of fish to soy meals feed from two aspects of tryptophan metabolism and intestinal flora changes.

The present study aims to investigate the effects of ratios of fish-to-soybean oils in a low fishmeal diet containing Clostridium autoethanogenum protein (CAP) on the growth and metabolism of Litopenaeus vannamei. Four diet groups were designed and the basal diet (FM, 44% crude protein, 8.66% crude lipid, fish-to-soybean oil: 1.5:2.5) contained 25% fishmeal. After 40% of fishmeal protein was replaced by CAP, three different fish-to-soybean oil ratios (4:1, 1:1, and 1:4) were set to formulate three experimental diets, and referred as HF (high fish oil), MF (medium fish oil), and LF (low fish oil), respectively. Shrimp were distributed to four groups of three replicates, each with 40 shrimp in a 300-L tank and they were fed four times daily for 7 weeks before sampling. Results showed that the growth performance of shrimp fed the MF diet was significantly lower than those fed the FM diet, while the shrimp fed the LF diet showed better growth than the HF group. The reduction of the crude lipid content of the whole body, hemolymph total cholesterol (T-CHO), and low-density lipoprotein cholesterol (LDL-C) contents indicated an alteration in the lipid and cholesterol metabolism of shrimp. Compared to the FM group, the mRNA levels of fas in shrimp fed the HF diet were significantly downregulated, while the mRNA levels of delta-24-sr in the HF group were significantly upregulated. In addition, the mRNA levels of hmgcr and scp in shrimp fed the LF diet significantly upregulated compared to the FM group. Metabolomic results showed that multiple metabolic pathways were affected by diet factors, including several amino acid metabolisms, purine metabolism, energy metabolism, and glycerophospholipid metabolism. In conclusion, the reduction of the ratios of fish-to-soybean oils in the low fishmeal diet containing CAP can not only reduce the usage of fish oil and the cost of feed but also maintain the growth performance of shrimp.

Dietary low-fishmeal (FM) have negative impacts on growth performance and metabolic responses in aquatic animals, while Schizochytrium limacinum have multiple benefits due to its rich contents of docosahexaenoic acid (DHA). However, little information is available on the effects of S. limacinum on Pacific white shrimp (Litopenaeus vannamei) in a low-FM diet (LF). An 8-week feeding trial were used to investigate the impacts of S. limacinum on growth performance, as well as morphological changes, biochemical indicators, antioxidant capacity, and transcriptomic profiles of hepatopancreas in shrimp fed a low-FM diet. Compared to LF diet, 0.3% S. limacinum (LFLD) diet significantly decreased the specific growth rate (SGR), and did not affect the feed conversion rate (FCR) and weight gain rate (WGR); whereas 0.6% S. limacinum (LFHD) diet did not affect the SGR, FCR and WGR. Histological structures of hepatopancreas showed that LFLD and LFHD treatments reduced the number and size of secretory cells and increased the number of storage cells, compared to LF group. LFLD and LFHD diets significantly decreased the concentrations of triglyceride and total cholesterol, significantly increased the levels of glutathione peroxidase and total antioxidative capacity, while did not affect the levels of malondialdehyde and superoxide dismutase. A total of 135 differential expression genes (DEGs) were identified in LFLD group and 108 DEGs were identified in LFHD group (both compared to LF group). Administration of S. limacinum altered the transcriptomic profiles, while LFHD induced a pattern similar to that of LF. LFLD and LFHD treatments mainly affected the 9 KEGG metabolic pathways, including “Arachidonic acid metabolism” and “Glutathione metabolism”. In conclusion, LFLD treatment impaired the growth performance of shrimp, while LFHD treatment did not affect it; and both treatments improved the morphological structure, lipid accumulation and antioxidant capacity of hepatopancreas.

An 8-weeks feeding trial was conducted to evaluate the effects of dietary cholesterol supplementation on growth performance, hemolymph biochemical parameters, cholesterol metabolism, intestinal health, and disease resistance of Pacific white shrimp (Litopenaeus vannamei) fed a low fishmeal diet. Four experimental diets including HFM (25% fishmeal), LFM (15% fishmeal+10% soy protein concentrate), LC1 (LFM+0.6 g kg−1 cholesterol), and LC2 (LFM+1.2 g kg−1 cholesterol) were formulated, each diet was fed to quadruplicate tanks with 40 shrimp (0.33 ± 0.03 g) per tank for 56 days. The results shown that cholesterol supplementation in the diet did not affect the growth performance of Litopenaeus vannamei (P > 0.05), but the crude lipid content significantly reduced in the LC2 group than that in HFM group (P

Abstract We investigated the effects of low and high doses of β-conglycinin and the ameliorative effects of sodium butyrate (based on high-dose β-conglycinin) on the growth performance, serum immunity, distal intestinal histopathology, and gene, protein expression related to intestinal health in hybrid grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂). The results revealed that the instantaneous growth rate (IGR) of grouper significantly increased, decreased, and increased in the low-dose β-conglycinin (bL), high-level β-conglycinin (bH) and high-level β-conglycinin plus sodium butyrate (bH-NaB), respectively. The feed coefficient ratio (FCR) was significantly increased in the bH and bH-NaB, serum levels of IFN-γ, IL-1β, and TNF-α were upregulated in the bH. The intestinal diameter/fold height ratio was significantly increased in the bH. Furthermore, there were increases in nitric oxide (NO), total nitric oxide synthase (total NOS), and peroxynitrite anion (ONOO−) in the bH, and decreases in total NOS and ONOO− in the bH-NaB. In the distal intestine, IL-1β and TGF-β1 mRNA levels were downregulated and upregulated, respective in the bL. The mRNA levels of TNF-α and IL-6 were upregulated in the bH, and downregulated in the bH-NaB, respectively. Occludin, claudin3 and ZO-3 mRNA levels were upregulated in the bL, downregulated in the bH and then upregulated in the bH-NaB. No significant differences were observed in the mRNA levels of IFN-γ and jam4. And the p-PI3K p85Tyr458/total PI3K p85 value was significantly increased in the bH and then decreased in the bH-NaB, and the total Akt value was significantly increased in the bH. These indicate β-conglycinin has a regulatory effect on serum immunity and affect distal intestinal development by modulating distal intestinal injury-related parameters. Within the distal intestinal tract, low- and high-dose β-conglycinin differentially affect immune responses and tight junctions in the distal intestine, which eventually manifests as a reduction in growth performance. Supplementing feed with sodium butyrate might represent an effective approach for enhancing serum immunity, and protects the intestines from damage caused by high-dose β-conglycinin.

This experiment was conducted to determine the optimum amount of corn distillers dried grains with solubles (DDGS) in the diet of juvenile hybrid grouper by studying the effect of DDGS on the growth, intestinal morphology, and mRNA expression levels. The diets were formulated with 45% fishmeal (FM) as the control group (D0). Six iso-nitrogenous and iso-lipidic diets were formulated using DDGS to replace 6.67%, 13.33%, 20%, 26.67%, and 33.33% of the FM protein (D1, D2, D3, D4, and D5, respectively). A total of 720 juvenile hybrid groupers with uniform body weight (11.88 ± 0.05 g) were selected from six treatments and four replicates (30 fish each) and farmed for 56 d. No significant effect of DDGS substitution for FM was found on survival rate (SR) and the feed conversion rate (FCR) (P > 0.05), but weight gain rate (WGR) and specific growth rate (SGR) of the control, 6.67%, and 13.33% groups were significantly higher than those of the other groups (P

This investigation aimed at estimating the effects of two zinc (Zn) sources and dietary Zn levels on growth performance, serum biochemical and immune indexes and zinc content of tissues. There were two Zn sources, Zn sulphate heptahydrate (Zn-S) and Zn methionine (Zn-M) with five addition gradients (10, 20, 40, 60, 80 mg/kg), separately, added to the isonitrogenous and isolipidic basal diets. The group without additional Zn supplement served as the control group. In the eight-week experiment, Litopenaeus vannamei (0.34 g initial body weight) was fed 11 kinds of experimental diets respectively (shared control group) for 8 weeks. The results indicated that: 1) dietary Zn-S and Zn-M significantly improved weight gain rate (WGR), specific growth rate (SGR), protein efficiency rate (PER) of shrimp (P 0.05). WGR, SGR, PER and FCR were not influenced by Zn sources and IZSL (P > 0.05) while they were significantly influenced by Zn levels (P 0.05). In conclusion, dietary Zn-M and Zn-S both improved growth performance and immunity of shrimp. Based on WGR and Zn content of the whole body, the optimum requirements of Zn in Zn-S or Zn-M for shrimp were 93.36 ~ 112.28 mg/kg and 66.03 ~ 103.61 mg/kg. Additionally, Zn-M exhibited higher avail and immunity and was recommended in diets of Litopenaeus vannamei.

BackgroundAt present, fish meal (FM) resources are in short supply, and competition for food between humans and animals is becoming increasingly critical. Finding non-grain protein sources that can replace FM is the key to solving the rapid development of aquaculture.MethodsSeven trial diets were prepared with 0 g/kg (EP0), 30 g/kg (EP3), 60 g/kg (EP6), 90 g/kg (EP9), 120 g/kg (EP12), 150 g/kg (EP15), and 180 g/kg (EP18) of enzyme-digested poultry by-product meal (EPBM) by replacing of FM. A total of 630 hybrid groupers (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂) were equally portioned into 21 tanks. At 8:00 and 16:00 each day, groupers were fed until they were full for a cumulative period of 8 weeks.ResultsThe results showed that 30 g/kg of EPBM significantly increased the rates of weight gain and special growth (P < 0.05). Significantly higher activities of serum glutamic pyruvic transaminase, glutamic oxaloacetic transaminase, catalase, and superoxide dismutase were observed in the EP3 group (P < 0.05). The categories and numbers of the top 10 dominant bacteria in the phylum and genus levels were not significantly influenced by feed (P > 0.05). In the proximal intestine and distal intestine, there were significantly higher expressions of SNAT3, LAAT1, CAT2, and CAT1 in the EP3 group compared with the EP0 group (P < 0.05). In the EP3 group, the expressions of PepT1, LAAT1, B0, +AT, and CAT2 were significantly increased in MI than those in all other groups (except the EP0 group, P < 0.05).ConclusionWhen FM was replaced by 30 g/kg of EPBM, growth performance, antioxidant capacity, and the ability to transport amino acids and peptides of hybrid grouper were significantly improved.

Glycerol monolaurate (GML), a representative fatty acid glyceride, was used to promote growth. This study investigated the effects of GML in diets on growth, serum biochemical parameters, antioxidant capacity, liver morphology and lipid metabolism for juvenile pompano Trachinotus ovatus. Six groups of T. ovatus (mean weight = 14.00 ± 0.70 g) were fed with six diets, containing varying GML levels of 0.00% (G0), 0.05% (G5), 0.10% (G10), 0.15% (G15), 0.20% (G20), and 0.25% (G25) for 8 weeks. Fish were reared for in floating cages (length: 1 m; width: 1 m; and height: 2 m). The highest weight gain rate (WGR), specific growth rate (SGR), and protein deposit rate (PDR) were observed in the G15 group (P < 0.05). Hepatic glutathione peroxidase, total antioxidant capacity and superoxide dismutase activities were significantly increased in the G10 and G15 groups compared with the G0 group (P < 0.05), whereas hepatic malondialdehyde (MDA) was significantly reduced in the G10 and G15 groups (P < 0.05). The alkaline phosphatase activity was significantly higher in the G5, G10, G15, and G20 groups than in the G0 group (P < 0.05), and the highest AKP activity was observed in the G15 group. Alanine aminotransferase (ALT) activity was significantly lower in the G10, G15, G20, and G25 groups than in the G0 group (P < 0.05). The addition of GML to the feed significantly reduced triglyceride (TG) content (P < 0.05). In comparison with the G0 group, the G15, G20, and G25 groups had significantly lower total cholesterol content and significantly higher high-density lipoprotein content (P < 0.05). Low-density lipoprotein content was significantly lower in the G5 and G10 groups than in the G0 group (P < 0.05). Serious vacuolation occurred in the G0 group, but the cell boundaries in all added groups were obvious, and the rate of intracellular vacuolization decreased. As the GML level increased, carnitine palmitoyl-transferase Ι mRNA level was significantly up-regulated (P < 0.05). The expression of fatty acid synthesis in the G10, G15, G20, and G25 groups was significantly lower than that in the G0 group (P < 0.05). The expression of sterol regulatory element-binding protein-Ι was significantly lower in the G10, G15, G20, and G25 groups than in the G0 group (P < 0.05). Based on the broken-line model of WGR and PDR corresponding to GML levels, the optimum addition level of dietary GML was 0.14%-0.16% for juvenile T. ovatus. In conclusion, 0.15% GML significantly improved the growth performance, hepatic antioxidant ability, and lipid metabolism and protected the liver for juvenile pompano T. ovatus.

Oxidized fish oil, as a harmful ingredient in feed, has a negative impact on aquatic animals. But the effect of oxidized fish oil on hybrid grouper (♀ Epinephelus fuscoguttatus × ♂ Epinephelus lanceolatus), especially the intestinal flora, is not yet understood. In the current study, a 65-day raising experiment with diets containing 0 g/kg, 30 g/kg, 60 g/kg, and 90 g/kg oxidized fish oil was performed (called as R, L, M and H group respectively) to investigate the effects of oxidized fish oil on growth performance, whole body composition, serum biochemical index, intestinal digestive enzyme activities and microbiome composition in juvenile hybrid grouper. Oxidized fish oil inhibited growth performance of pearl gentian grouper. The Moisture, crude protein, and ash content in whole body increased as increasing dietary oxidized fish oil content. The vitamin E content and antioxidant enzyme activity in serum including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) were significantly increased as the oxidized fish oil in the diet increased, but malondialdehyde (MDA) content in serum was significantly decreased. Meanwhile, the D-Lactate (D-LA) and interleukin-10 (IL-10) content in serum was promoted by oxidized fish oil, but interleukin-6 (IL-6) content was suppressed. Moreover, the intestinal digestive enzyme activities were promoted by oxidized fish oil. The oxidized fish oil reduced alpha diversity of intestinal bacteria. At the same time, oxidized fish oil changed the structure of grouper intestinal flora according to beta diversity and line discriminant analysis (LDA) effect size. In conclusion, oxidized fish oil inhibited growth performance, changed the composition of the body and caused oxidative stress and inflammation in the body, but it promoted the secretion of digestive enzymes in the intestine. More importantly, oxidized fish oil reduced the diversity of intestinal flora and changed the structure of intestinal flora.

As antibiotics-treated animal models provide good insights into the potential causes of the microbiota-dependent changes, we explored the effects of microbiota perturbation driven by a mixture of antibiotics on lipid metabolism and lipid deposition in the liver of hybrid grouper (Epinephelus fuscoguttatus♀ × E. lanceolatus♂) fed a bile acid diet in this study. Ninety groupers were randomly fed a bile acids diet (SBD) or a bile acids diet supplemented with antibiotics mixture (ASBD) for a short-term period. The results showed that ASBD treatment significantly decreased the level of hepatic lipid droplets, the content of hepatic triglycerides and total cholesterol, and serum low-density lipoprotein cholesterol, while significantly increasing the content of high-density lipoprotein cholesterol, compared to the SBD group. The fish fed ASBD showed significantly enhanced activities of lipolytic enzymes, expression of lipolytic proteins and transcriptional factors genes, whereas significantly reduced the expression of lipogenic transcriptional factor genes. In addition, the antibiotics treatment significantly increased the abundance of Bacteroidetes, while non-significantly decreasing the Firmicutes/Bacteroidetes ratio (p = 0.061). No significant shifts were observed in the α-diversity indices in SBD and ASBD groups, although the structures and potential functions of the intestinal microbiota were clearly separated. In conclusion, the antibiotics treatment reduced the lipid deposition and altered lipid metabolism via mainly enhancing hepatic lipolysis and slightly reducing hepatic lipogenesis.

Octanoate is a type of classical medium-chain fatty acids, which is widely used to treat neurological and metabolic syndrome. However, the specific role of octanoate in repairing intestinal health impairment is currently unknown. Therefore, we investigated whether dietary octanoate repaired the intestinal damage induced by surplus soybean oil in Larimichthys crocea. In this study, dietary octanoate alleviated abnormal morphology of the intestine and enhanced expression of ZO-1 and ZO-2 to improve intestinal physical barrier. Further, dietary octanoate increased antioxidant enzymic activities and decreased the level of ROS to alleviate the intestinal oxidative stress. Dietary octanoate also attenuated the expression of proinflammatory cytokines and the polarity of macrophage to reduce the intestinal inflammatory response. Moreover, the result of intestinal microbial 16S rRNA sequence showed that dietary octanoate repaired the intestinal mucosal microbial dysbiosis, and increased the relative abundance of Lactobacillus. Dietary octanoate supplementation also increased the level of acetic acid in intestinal content and serum through increasing the abundance of acetate-producing strains. Overall, in Larimichthys crocea, dietary octanoate might alleviated oxidative stress, inflammatory response and microbial dysbiosis to repair the intestinal damage induced by surplus soybean oil. This work provides vital insights into the underlying mechanisms and treatment strategies for intestinal damage in vertebrates.

Abstract The purpose of subject was to explore the optimum protein requirement of juvenile grouper (Epinephelus coioides). In the test, 450 juveniles with an average weight (10.02 ± 0.22) g were randomly divided into six groups with triplicate, and were fed with 350, 400, 450, 500, 550 and 600 g/kg iso-lipid test diet twice 1 day for 8 weeks, respectively. The results showed that: (1) With the increase of protein level, the body weight gain rate and specific growth rate first increased and then reduced, while the feed coefficient rate first decreased and then increased, while the protein efficiency significantly decreased (P

Understanding the molecular mechanisms involved in adaptation to alternate diets has become a significant concern, as increasing amounts of fishmeal (FM) protein in aquafeeds are being substituted with plant protein. Thus, the goal of this study was to assess growth performance, quality, and liver function of juvenile Sillago sihama (S. sihama) through growth indices, whole-body composition, histology of the liver, and RNA-sequencing (RNA-seq), after they were fed a formulated diet with 64% low-gossypol cottonseed meal (LCSM) for 56 days, compared to those fed a traditional FM-based diet. Indicators of growth, including final body weight (FBW), weight gain rate (WGR), specific growth rate (SGR), protein efficiency ratio (PER), and condition factor (CF), were considerably lower in the 64% LCSM (R64) group than in the FM diet group. In the R64 diet, the whole crude lipid was significantly lower than in the FM diet. The hematoxylin–eosin section showed that dietary high levels of LCSM resulted in diffuse lipid vacuolation in the liver of S. sihama. According to a liver transcriptome analysis, high LCSM intake in the diet significantly impacted lipid synthesis and catabolism, elevated pathways for cholesterol synthesis, blocked several amino acid metabolic pathways, and adversely affected hepatic gluconeogenesis and glycolysis. The findings of this study indicate that feeding high levels of LCSM in S. sihama is harmful to the growth of the organism and can harm the liver’s structural integrity, as well as obstruct the normal metabolism of amino acids, lipids, and carbohydrates. Therefore, it is not recommended to substitute LCSM for high levels of FM in the diet of S. sihama.

The effect of hydrolysed fish protein powder (HFP) on the growth, aspartate transaminase (AST) and alanine transaminase (ALT) content in the serum, malondialdehyde (MDA) and superoxide dismutase (SOD) content in the hepatopancreas, total protease, trypsin, and chymotrypsin in the intestine of Pacific white shrimp (Litopenaeus vannamei) was assessed after an 8-week experiment. Pacific white shrimps were fed six isonitrogenous (39%) and isolipidic (8%) diets with 0% (CT), 1% (T1), 2% (T2), 2.5% (T3), 3% (T4) and 4% (T5) HFP. A positive effect on weight gain rate, survival rate and feed conversion ratio was observed in shrimp fed HFP diets. In the serum, AST and ALT levels were significantly high in the T1 group compared to the other groups (P < 0.05). Total protease, trypsin and chymotrypsin were significantly high in the T4 group than in the CT group (P < 0.05). The insulin-like growth factor-I mRNA expression level in the intestine, hepatopancreas and muscle were significantly high in shrimp fed HFP diet compared to the CT group (P < 0.05). Muribaculaceae, Lactobacillus, and Lachnospiraceae were the most abundant bacteria at the genus level in the intestine. Results from this study suggest HFP has a positive effect on the growth and intestinal development of Pacific white shrimp.

This experiment was conducted to determine the optimum amount of peanut cake (PNK) in the diet of hybrid grouper by studying the effect of PNK on the growth, antioxidant capacity, liver fat metabolism, and intestinal microbiota composition by replacing fish meal (FM) protein in the diet of the juvenile hybrid grouper. A total of 840 juvenile hybrid grouper with uniform body weight (13.20 ± 0.05 g) were selected from 7 treatments and 4 replicates (30 fish each) farmed for eight weeks. Results showed that the weight gain rate (WGR) of the low-substitution group was significantly higher than that of the high-substitution group (P

Little is known about the association of bile acids (BAs) with lipid deposition and lipid metabolism of fish in vitro. In the present study, we established the model of fatty-degenerated hepatocytes in pearl gentian grouper (Epinephelus fuscoguttatus♂ × Epinephelus lanceolatus♀), and explored the effects and mechanism of BAs regulating on lipid metabolism in this model. The results showed that fatty-degenerated hepatocytes induced by lipid emulsion accumulated the intracellular triglyceride (TG), the enhanced expression of sterol responsive element binding protein 1 (SREBP1) protein, and the repressed expression of peroxisome proliferator-activated receptor alpha (PPARA), and phosphorylated PPARA (P-PPARA) proteins. BAs co-incubation reduced the content of TG, while increasing the expression of PPARA, farnesoid X receptor (FXR), and G protein-coupled bile acid receptor 1 (TGR5) proteins. Activation of FXR by INT-747 reduced the content of TG, while down-regulating the expression of SREBP1 and PPARA, and up-regulating the expression of P-PPARA, FXR, small heterodimer partner (SHP), and TGR5. Inhibition of FXR by guggulsterone increased the level of TG, while decreasing the expression of TGR5, increasing the expression of SHP. Activation of TGR5 by INT-777 reduced the content of TG, while down-regulating the expression of SREBP1 and SHP, up-regulated the expression of TGR5. Inhibition of TGR5 by SBI-115 elevated the level of TG, while reducing the expression of P-PPARA and TGR5. In conclusion, the FXR and/or TGR5 signaling pathways which were inhibited in fatty-degenerated hepatocytes from pearl gentian grouper, were activated after BAs co-incubation, then altering the lipid metabolism by repressing lipogenesis and enhancing lipolysis, and regulating transcriptional factors, thus reduces the lipid accumulation in vitro.

The effect of hydrolyzed fish protein powder (HFP) on the growth, intestinal development, gene mRNA expression, and enzyme activity in the intestine and liver of juvenile hybrid grouper (Epinephelus fuscoguttatus ♀ and Epinephelus lanceolatus ♂) was assessed after an 8-week feeding trial. Seven isonitrogenous (50%) and isolipidic (9%) diets were fed to hybrid grouper with 0% (CT), 1% (H1), 1.5% (H2), 2% (H3), 2.5% (H4), 3% (H5), and 4% (H6) HFP. No significant difference (p > 0.05) in weight gain rate (WGR), specific growth rate (SGR), feed conversion ratio (FCR), and survival rate (SR) was observed in all the groups. The crude protein content in the H6 group was significantly higher than in the other groups (p < 0.05). Intestinal lipase and trypsin activity were significantly higher in H3 and H5 groups (p < 0.05). In the serum, superoxide dismutase (SOD) activity was significantly higher in H5 and H6 groups, while malondialdehyde (MDA) activity was lower (p < 0.05) compared to other treatments. Insulin-like growth factor (IGF-I) and target of rapamycin (TOR) mRNA expression levels in the intestine and muscle were significantly higher in the H2 group and H1 group (p < 0.05), respectively. The most abundant intestinal bacteria found at the genus level are Acinetobacter, Vibrio, and Flavobacteriaceae. The villus was significantly longer in hybrid grouper fed with different levels of HFP compared to the control, and fish in the H2 group had thicker intestinal muscle compared to the other groups (p < 0.05). In conclusion, the addition of HFP to the low fishmeal (FM) diets of juvenile grouper improved the intestinal development and increased the levels of intestinal digestive enzymes.

This study evaluated the effects of lipid sources on the replacement of fishmeal with Clostridium autoethanogenum protein (CAP) in the diet of Pacific white shrimp (Litopenaeus vannamei). By using CAP to replace 40% fishmeal in the basal diet (contains 25% fishmeal), four diets (PC as the control diet, LSO as the low soybean oil level, MSO as the middle soybean oil level, and HSO as the high soybean oil level) were formulated by adding different proportions of fish oil and soybean oil. Each diet was assigned to four replicates (40 shrimps per replicate, initial weight = 1.79 ± 0.02 g). A 7-day Vibrio parahaemolyticus challenge test was conducted at the end of the 50-day feeding experiment. Weight gain was significantly higher and the cumulative mortality after challenge was lower in HSO treatment. The total antioxidant capacity (T-AOC) in hepatopancreas was significantly raised with increasing dietary soybean oil based on CAP substitution. After challenge, Pen3 mRNA expression was significantly higher in hepatopancreas and NF-κB pathway-related mRNA (dorsal, relish, and IKKβ) expression was higher in the intestine in HSO treatment. The height of mucosal folds and the thickness of the muscle layer were positively correlated with the level of dietary soybean oil. Transmission electron microscopy (TEM) analysis showed that the microvilli were damaged and the endoplasmic reticulum was swollen in shrimp fed the LSO diet. Diversity of intestinal microbiota was increased in shrimp fed the LSO diet, with a significant increase in beneficial bacteria such as Halocynthiibacter and Ruegeria as well as less harmful bacteria such as Vibrio. These results suggested that the replacement of fishmeal with CAP and the high proportion of soybean oil in the diet could improve the growth performance, disease resistance, and intestinal structure of Pacific white shrimp, and high fish oil in a low-FM diet raised the percentage of beneficial bacteria in the intestine of shrimp.

This study investigated the effects of dietary supplementation of ESTAQUA® yeast culture (YC) on the growth, immunity, intestinal microbiota, and disease-resistance against Vibrio harveyi in hybrid grouper (♀Epinephelus fuscoguttatus×♂E. lanceolatus) at 0% (C0), 2% (N1), and 4% (N2). After 8 weeks of the feeding trial, the results indicated that the survival rate (SR), weight gain rate (WGR), and specific growth rate (SGR) of hybrid grouper were significantly higher in the N1 (2%) and N2 (4%) group than those in the control group (P

Fish oil is an important source of lipid in aquafeeds, but is prone to oxidation. In aquatic species, oxidized fish oil may induce oxidative stress. Although the intestine is an essential nutritional and immunological organ in juvenile hybrid grouper (Epinephelus fuscoguttatus × Epinephelus lanceolatus), the cause of its oxidative stress remains unknown. In the current research, a 65-day rearing experiment with diets containing 0% (R), 3% (L), 6% (M), or 9% (H) oxidized fish oil was conducted to explore the effects of oxidized fish oil on the antioxidant ability, histology, and transcriptome of the intestine in juvenile hybrid grouper. The concentrations of vitamin E and antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) in the foregut, midgut, and hindgut decreased significantly with the level of oxidized fish oil in the diet rose, whereas malondialdehyde (MDA) concentration increased. The oxidative stress damaged intestinal tissue structure. In detail, the goblet cell in H group was significantly reduced and the microvilli was depauperated. Compared with group R, the oxidized stress altered the intestinal transcriptome map in H group. A total of 29,360 unigenes had been annotated in all databases. There were 18 differentially expressed genes (DEGs), with 12 being up-regulated and 6 being down-regulated. According to the GO enrichment, the functions of differential genes were mostly enriched in primary metabolic process, cellular biosynthetic process, organic substance biosynthetic process, cellular macromolecule metabolic process, and protein metabolic process. There were 2 significant pathways including sulfur metabolism pathways and p53 signaling pathways involving cytochrome c (Cyt2c) gene with a high expression state under oxidative stress. In summary, oxidized fish oil induced intestinal oxidative stress. Meanwhile, oxidative stress was destroying the structure of the gut tissue. Furthermore, oxidative stress altered the intestinal transcriptome map.

The present study was conducted to investigate the effect of fish meal replacement with Clostridium autoethanogenum protein (CAP) on growth performance, haemato-biochemistry, digestive capacity, antioxidant index, and histopathological examination of liver and intestine in largemouth bass (Micropterus salmoides). Seven experimental diets were formulated with CAP replacement of 0% (CAP0), 15% (CAP15), 27% (CAP27), 39% (CAP39), 51% (CAP51), 63% (CAP63) and 75% (CAP75) fish meal, respectively. Results showed that replacement of fish meal by CAP did not affect SR, FBW, WGR, SGR and CF. While the fish fed diets containing CAP displayed a higher PER and a lower FCR than the control group (P 0.05). Additionally, The ADC of dry matter and protein were improved by addition of CAP (P 0.05). The lipase and amylase activities were not dramatically altered in stomach (P > 0.05), but were significantly increased in intestine with dietary substitution level up to 39% (P

Fish oil oxidation can produce harmful substances, but the specific effects of oxidized fish oil on liver function in the hybrid grouper (♀ Epinephelus fuscoguttatus × ♂ Epinephelus lanceolatus) are not yet clear. In the present study, hybrid grouper was fed diets containing 0, 3, 6, or 9% oxidized fish oil (referred to as the control, L, M, and H groups respectively) for 65 days to investigate its effects on liver physiology. Oxidized fish oil significantly decreased protein content in liver (P

In the present study, juvenile hybrid grouper (Epinephelus fuscoguttatus♀ × E. lanceolatus♂) were intraperitoneally injected with taurocholic acid (I-TCA), obeticholic acid (FXR agonist, I-T747), guggulsterone (FXR antagonist, I-TGU), SBI-115 (TGR5 antagonist, I-TSBI), and INT-777 (TGR5 agonist, I-T777), respectively. The results showed that the fish injected with 50 mg kg−1 TCA three times during a 144 h period exhibited significantly lower hepatic lipid accumulation, compared to other concentrations and periods. Compared to the I-TCA group, the I-T747 treatment significantly increased the activities of hepatic adipose triglyceride lipase (ATGL) and carnitine palmitoyltransferase 1 (CPT1), as well as the expression of lipolysis and fatty acid uptake genes, while significantly decreased the conten of hepatic crude lipid, the activity of CPT1, and the expression of lipogenesis genes. Meanwhile, the I-TGU treatment significantly increased hepatic lipid deposition and the expression of lipogenesis genes. Compared to the I-TCA group, the I-T777 treatment did not significantly affect the parameters related to lipid deposition, but it significantly decreased the activities of acetyl-CoA carboxylase (ACC), CPT1, and fatty acid synthase (FAS), while significantly increasing the activity of ATGL and the expression of lipolysis and fatty acid uptake-related genes. Meanwhile, the I-TSBI treatment significantly increased the hepatic lipid accumulation, the activities of ACC, CPT1 and FAS, and the expression of lipogenesis and lipogenic transcriptional factors genes. In conclusion, activation of the FXR protected against the hepatic lipid accumulation by enhancing the lipolysis, while inhibition of FXR or TGR5 induced the hepatic lipid accumulation by enhancing the lipogenesis in hybrid grouper.