Search

An 8-week feeding trial was conducted to investigate the effects of LA supplementation in a high-fat diet on the growth performance, hepatic antioxidant capacity, and glycogen metabolism of largemouth bass (Micropterus salmoides). Five diets were formulated including control diet (11.55 % crude fat, CF), a high-fat diet (17.80 % crude fat, HF) and three HF diets supplemented with 0.15 %, 0.20 % and 0.25 % LA (HL0.15, HL0.20 and HL0.25, respectively). In this experiments, HL0.15 and HL0.20 could improve the uniform for the growth of the largemouth bass, while adding 0.25 % did not significantly improve growth. The highest viscerosomatic index (VSI) and hepatosomatic index (HSI) were measured in fish fed the HF diet. Compared to the fish fed HF diet, fish fed HL diets showed lower serum total triglyceride (TG), alanine aminotransferase (ALT), aspartate aminotransferase (AST), hepatic malondialdehyde (MDA) and glycogen levels, and higher hepatic catalase (CAT) and glutathione peroxidase (GSH-PX) activities. In addition, the mRNA expression for lipolysis genes in fish liver were increased and for gluconeogenesis and fatty acid synthesis were reduced. The transcript levels of apoptosis-related genes were significantly down-regulated in the liver of largemouth bass in HL0.15 and HL0.20 groups compared to the HF group. Moreover, compared with the HF group, the mRNA expression of pro-inflammatory factors was significantly reduced in HL groups, and the histomorphology of the liver were significantly improved. These results suggested that LA supplementation in high-fat diets could improve lipid utilization, glycogen accumulation, antioxidant capacity of fish liver, thus reduce the adverse effects of high fat diets on fish, and then improve the growth performance of largemouth bass., Competing Interests: Declaration of competing interest The authors declare that they have no conflict of interest., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Glutamine addition can improve immunity and intestinal development in fish. This study examined the protective roles of glutamine on growth suppression and enteritis induced by glycinin in juvenile hybrid groupers (female Epinephelus fuscoguttatus × male Epinephelus lanceolatus). The experiment set four isonitrogenous and isolipidic trial diets: a diet containing 10% glycinin (11S), 10% of 11S diet supplemented with 1% or 2% alanine-glutamine (1% or 2% Ala-Gln), and a diet containing neither 11S nor Ala-Gln (FM). A feeding trial was conducted in hybrid grouper for 8 weeks. Weight gain and specific growth rates in Groups 1% and 2% Ala-Gln were significantly higher than those of the 11S group but were similar to those of the FM group. The intestinal muscular layer thickness, plica height and width of the 2% Ala-Gln group were significantly higher than those of Group 11S. The enterocyte proliferation efficiency of the 11S group was significantly lower compared to other groups. Compared with the 11S group, Groups 1% and 2% Ala-Gln fish had increased intestinal lysozyme activities, complement 3 and immunoglobulin M as well as cathelicidin contents. The mRNA levels of tnf-α, il-1β, ifn-α, and hsp70 genes were more downregulated in Groups 1% and 2% Ala-Gln than in Group 11S. Compared with FM group, fish from the 11S group had significantly lower mRNA levels of myd88, ikkβ, and nf-κb p65 genes. These three values in the 2% Ala-Gln group were significantly lower than those in Group 11S but not significantly different from those of Group FM. The relative abundance of Vibrio in Group 11S was higher than that in Groups FM and 2% Ala-Gln. Intestinal glutamine, glutaminase, glutamic acid, α-ketoglutarate, malate dehydrogenase and ATP contents were higher in Groups 1% and 2% Ala-Gln than in Group 11S. These results suggest that glutamine is a useful feed additive to enhance growth and intestinal immunity, alleviate inflammation, and modulate gut microbiota in hybrid grouper fed high-dose glycinin., Competing Interests: Declaration of competing interest There are no conflicts to declare., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

The study evaluated the effects of dietary phosphorus supplementation on the fishmeal replacement with Clostridium autoethanogenum protein (CAP) in the diet of L. vannamei. Four isonitrogenous and isolipid diets were formulated: the PC diet contains 25% fishmeal, the NC, P1 and P2 diets were replaced 40% fishmeal with CAP and supplemented with 0, 0.8 and 1.6% NaH 2 PO 4 respectively (equivalent to dietary phosphorus level of 0.96%, 1.12% and 1.27%). Sampling and V. parahaemolyticus challenge test were conducted after 50-day-feeding (initial shrimp weight 1.79 ± 0.02 g). The results showed that there were no significant differences in the growth performance of shrimp among the 4 groups. The expressions of dorsal in the gut were significantly lower in shrimp fed the P1 and P2 diets than shrimp fed the NC diet and the expression of peroxinectin in the gut was lower in shrimp fed the NC diet than others. The cumulative mortality of shrimp after V. parahaemolyticus challenge was significantly lower in shrimp fed the P2 diet than those fed the NC diet. After the challenge, genes expressions related to the prophenoloxidase activating system (proPO, lgbp, ppaf) were inhibited in the hepatopancreas of shrimp fed NC diet but activated in shrimp fed the P1 diet compared to those fed the PC diet. The AKP and T-AOC activities were higher in shrimp fed the P2 diet than those fed the other diets. The thickness of muscle layer of shrimp fed the P1 diet was thicker than that in the other groups, and significant stress damage happened in the midgut of the shrimp fed the NC diet. The abundance of Pseudoalteromonas, Haloferula and Ruegeria in shrimp fed the P1 diet was higher than those fed the other diets, while Vibrio in shrimp fed the P2 diet was higher than those fed the other diets. This indicated that a low fishmeal diet with dietary phosphorus level of 1.12% could improve the histology, enhance immune response, and increase the abundance of beneficial bacteria in the gut of shrimp. The low fishmeal diet with dietary phosphorus level of 1.27% could improve disease resistance and antioxidant capacity, but there was a possibility of damage to the gut histology as well as increasing abundance of Vibrio in the gut microbiota of shrimp., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Artemisinin (ART) is a kind of Chinese herbal medicine worth exploring, which obtains various physiological activities. In order to study the prebiotic effect of ART on Litopenaeus vannamei fed cottonseed protein concentrate meal diets, six groups of isonitrogenous and isolipid diets were prepared (including the fish meal control group, FM; cottonseed protein concentrate replacing 30% fishmeal protein and supplementing ART groups: ART0, ART0.3, ART0.6, ART0.9, and ART1.2). The feeding trials was lasted for 56 days. The results showed that the final body weight, weight gain and specific growth rate of the ART0.6 group were the highest, yet the feed coefficient rate of the ART0.6 group was the lowest significantly (P < 0.05). There was no significant difference in survival rate among treatments (P > 0.05). In serum, the content of malondialdehyde in ART0 group was the highest (P < 0.05); the activities of superoxide dismutase, catalase, phenol oxidase and lysozyme increased firstly and then decreased among the ARTs groups (P < 0.05). The activities of intestinal digestive enzymes (including the trypsin, lipase and amylase) showed an upward trend among the ARTs groups (P < 0.05). The histological sections showed that the intestinal muscle thickness, fold height and fold width in the FM group were significantly better than those in the ART0 group; while the mentioned above morphological indexes in the ART0 group were significantly lowest among the ARTs groups (P < 0.05). Sequencing of intestinal microbiota suggested that the microbial richness indexes firstly increased and then decreased (P < 0.05); the bacterial community structure of each treatment group was almost close; the relative abundance of pathogenic bacteria decreased significantly (P < 0.05), such as the Proteobacteria and Cyanobacteria at phylum level, besides the Vibrio and Candidatus Bacilloplasma at genus level. In intestinal tissue, the relative expression levels of TOLL1, TRAF6 and Pehaeidih3 showed up-regulated trends, while the expression of Crustin and LZM firstly up-regulated and then down-regulated (P < 0.05). The challenge experiment suggested that the cumulative mortality of FM group was significantly lower than that of ART0 group; besides the cumulative mortality firstly increased and then decreased between the ARTs groups (P < 0.05). In conclusion, the dietary supplementation of ART can improve the growth, antioxidant capacity, immune response, gut health and disease resistance of the shrimp. To be considered as a dietary immune enhancer, the recommended supplementation level of ART in shrimp's cottonseed protein concentrate meal diets is 0.43%., Competing Interests: Declaration of competing interest The authors declare that they have no competing interests., (Copyright © 2022. Published by Elsevier Ltd.)

In order to evaluate the effects of glycerol monolaurate (GML) on the growth performance, immunology function, disease resistance and intestinal microbiota for hybrid groupers. Seven levels of GML (0, 600, 1200, 1800, 2400, 3000 and 3600 mg/kg) were added to diets and were noted as the G1 (control group), G2, G3, G4, G5, G6 and G7, respectively. Each experimental diet was fed to triplicate groups of 30 juvenile groupers for 8 weeks. The FBW, WGR and SGR were significantly higher and FCR was significantly lower in the G4 group compared to the G1 group (P < 0.05). Serum immune enzyme activities (ACP, AKP and LZM) rose and then fell and had the highest values in the G4 group (P < 0.05). The expression of TNF-α and IL6 in head kidney was significantly inhibited (P < 0.05), while the expression of TLR22 was increased (P < 0.05). After the Vibrio parahaemolyticus challenge test, ACP and AKP activities were increased in the G4 and G5 groups, while mortality was lower than in the G1 group (P < 0.05). GML significantly modulated the abundance of intestinal microbiota, with the G4 and G5 groups increasing the relative abundance of the Firmicutes and Bacillus, respectively (P < 0.05). The alpha diversity of the G5 group (Sob, Chao1 and ACE) was significantly higher than that of the G1 group (P < 0.05). In summary, the optimal level of GML was 1700 mg/kg according to the regression equation model fitted by the WGR index., Competing Interests: Declaration of competing interest The authors confirm that there was no conflict of interest with this experiment., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

An 8-week feeding trial was conducted to evaluate the effects of chenodeoxycholic acid (CDCA) on growth performance, body composition, lipid metabolism, and intestinal health of juvenile white shrimp, Litopenaeus vannamei fed a low fishmeal diet. Four practical diets were formulated: HFM (25% fishmeal), LFM (15% fishmeal), LB1 (LFM + 0.04% CDCA), LB2 (LFM + 0.08% CDCA). Each diet was assigned to four tanks with forty shrimp (initial weight 0.33 ± 0.03 g) per tank. The results indicated that the growth performance of shrimp were similar between the four groups; the crude lipid content of shrimp fed the LB2 diet was significantly lower than those fed the HFM diet (P < 0.05). The lipase activity content in hepatopancreatic were significantly higher in the two CDCA supplemented groups than that in LFM group; the contents of total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol in hemolymph were significantly lower in LFM group, LB1 group and LB2 group than that in HFM group (P < 0.05). The shrimp fed LB1 diet was significantly decreased the intestinal expression levels of tube than those fed in HFM diet; the intestinal gene expression of imd and toll were significantly lower in LB2 group than those in HFM group (P < 0.05). The results of hepatopancreas gene expression suggest that shrimp fed the LFM diet showed significantly upregulated expression levels of sterol regulatory element-binding protein (srebp), acetyl-CoA carboxylase (acc), and carnitine palmitoyltransferase 1 (cpt-1) than those fed the HFM diet; shrimp fed the LB1 diet showed significantly upregulated expression levels of srebp, acc, and AMP-activated protein kinase (ampk) than those fed the HFM diet; shrimp fed the LB2 diet had higher expression levels of srebp, acc, and cpt-1 than those fed the HFM diet (P < 0.05). In the hepatopancreas, the shrimp fed the LFM diet shown significantly up-regulated the expression levels of beclin1 compared to those fed HFM diet; the expression levels of autophagy-related protein13 (atg3), autophagy-related protein 12 (atg12) of in shrimp fed the LB1 diet were significantly higher than those fed the HFM diet; and the expression levels of autophagy-related protein13 (atg13), beclin1, atg3, atg12, autophagy-related protein 9 (atg9) of shrimp fed LB2 diet were significantly higher than those fed the HFM diet (P < 0.05). The atg3 in intestine of shrimp fed the LB2 diet were significantly higher than those fed the HFM diet (P < 0.05). Intestinal mucous fold were damaged, hepatic tubules were disorganized and B cells appeared to be swollen in LFM group. The fold height and width of shrimp fed the diets supplemented with CDCA increased significantly than those fed the LFM diet (P < 0.05), the hepatic tubules were neatly arranged, and R cells increased. In conclusion, supplementary CDCA in a low fishmeal diet promoted lipid metabolism, enhanced autophagy of shrimp, also improved the health of the intestine and hepatopancreas., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Clostridium butyricum (CB) is a gram-positive bacterium that secretes short-chain fatty acids such as butyric acid and so on. An 8-week feeding trial was conducted to investigate the effects of CB on the growth performance, antioxidant capacity, immunity and resistance to Vibrio parahaemolyticus in Litopenaeus Vannamei fed with cottonseed protein concentrate (CPC) replacement of fishmeal. Six iso-nitrogenous (40%) and iso-lipidic (6%) diets were formulated including a positive control group (PC, 25% fishmeal), a negative control group (NC, CPC replaced 30% of fishmeal protein), and 0.03% (C1, 3 × 10 8  CFU/kg), 0.12% (C2, 1.2 × 10 9  CFU/kg), 0.48% (C3, 4.8 × 10 9  CFU/kg) and 1.92% (C4, 1.92 × 10 10  CFU/kg) CB were supplemented on the negative control group (NC). After the feeding trial, the remaining shrimp in each treatment group were subjected to a challenge experiment with Vibrio parahaemolyticus. The results indicated that weight gain rate (WGR), specific growth rate (SGR) in C4 group were significantly lower than those in PC and C2 groups (P < 0.05); the feed conversion ratio (FCR) was significantly higher than that of PC and C2 groups (P < 0.05). There was no significant difference in survival rate (SR) among all groups (P > 0.05). Compared to the PC and NC groups, the total superoxide capacity, superoxide dismutase and lysozyme were significantly higher in the C4 group (P < 0.05); the glutathione peroxidase, acid phosphatase and alkaline phosphatase were significantly higher in the C3 group (P < 0.05); and the malondialdehyde was significantly lower in the C4 group (P < 0.05). The relative mRNA expressions of Toll receptor (TLR), innate immune deficiency gene (IMD), penaiedin3a (Pen3) were significantly down-regulated in the NC group than those in the PC group (P < 0.05). In addition, the relative mRNA expressions of TLR, IMD and Pen3 were significantly up-regulated in all groups supplemented with CB than those in the NC group (P < 0.05). Moreover, the cumulative mortality rate in the NC group was not significantly different from the PC group (P > 0.05) and was significantly higher than those in the C3 and C4 groups (P < 0.05). In conclusion, the CB supplementation on the basis of CPC replacement of 30% fishmeal protein enhanced significantly the antioxidant capacity, immunity and disease resistance of shrimp and improved its growth performance. Therefore, considering the factors of the growth, immunity and disease resistance, the CB supplementation of 0.12%-0.48% (1.2 × 10 9  CFU/kg-4.8 × 10 9  CFU/kg) was recommended in the diet of L. vannamei based on the results of this experiment., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

An 8-week feeding trial was conducted to investigate the influence of partial replacement of fishmeal (FM) by black soldier fly (BSF) (Hermetia illucens) on the growth, distal intestine morphology, intestinal flora, and intestinal immune response of pearl gentian grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂). Four diets were formulated, 0% (0 g kg -1 ), 10% (50 g kg -1 ), 20% (100 g kg -1 ) and 30% (150 g kg -1 ) fishmeal were replaced with BSF, named as FM, BSF10, BSF20, BSF30, severally. The study found that, with the increasing dietary BSF levels, growth and feed conversion ratio of fish decreased significantly (P < 0.05). Chitinase and trypsin activities were significantly increased with increasing dietary BSF levels (P < 0.05). With the increasing dietary BSF levels, distal intestinal muscularis thickness and mucosal fold length decreased significantly (P < 0.05), as well as total abundance of intestinal flora. The relative abundance of four phyla and six genera among the top 20 genera were significantly affected by dietary BSF levels (P < 0.05). With the increasing dietary BSF levels, the mRNA levels of nf-κbem1, r-cel and il-10 up-regulated significantly (P < 0.05). For fish fed BSF30 diet, the mRNA levels of myd88 and tlr22 were significantly higher than fish fed FM diet (P < 0.05). In conclusion, replacement fishmeal with BSF increased activity of digestive enzymes, but negatively affected growth performance and intestinal health of pearl gentian grouper., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

This study was carried out to investigate the effects of dietary vitamin A (VA) on growth performance, antioxidant capacity, digestion, intestinal immune response, and mRNA expression of intestinal tight junction proteins for juvenile hybrid grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂). Six isonitrogenous and isolipidic experimental diets were formulated to obtain VA levels (317, 1136, 2038, 4142, 7715, 15204 IU/kg diet, respectively). The triplicate groups of fish (average weight of 9.01 ± 0.27 g) were fed twice daily (8:00 and 16:00) for 7 weeks. Based on the broken-line analysis model of WG and LYZ activity, the dietary VA requirement of hybrid grouper were estimated to be 2688.58 and 4096.36 IU/kg diet. The results showed that VA deficiency or excess could reduce Weight gain, specific growth rate, and protein efficiency ratio, and increase feed conversion ratio and hepatosomatic index (P < 0.05). In addition, VA deficiency could reduce the serum activities of acid phosphatase (ACP), superoxide dismutase, and total antioxidant capacity and increase the malondialdehyde content (P < 0.05). VA deficiency also could reduce intestinal activities of ACP, alkaline phosphatase, lysozyme, complement 3, complement 4 contents, and activities of alpha-amylase, lipase, and trypsin (P < 0.05). Meanwhile, VA deficiency could reduce villus height in proximal intestine (PI) and mid intestine (MI), as well as muscle thickness in PI and distal intestine (DI) (P < 0.05). Moreover, VA deficiency could down-regulated antimicrobial peptides (β-defensin, Hepcidin [not in MI and DI], Epinecidin), anti-inflammatory cytokines (interleukin 10 and transforming growth factor β1 [not in DI]), tight junction proteins (occluding and claudin3) mRNA levels in the PI, MI and DI, and up-regulated pro-inflammatory cytokines (tumor necrosis factor α [not in MI] and interleukin 1β [not in MI]), signaling molecules c-Rel and p65 (P < 0.05). Collectively, VA deficiency could reduce growth performance because of a negative effect on intestinal health by depressing digestive abilities, intestinal morphology, immunity and tight junction function in the intestine., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Fish fed a high plant protein diet exhibit intestinal inflammation, the mechanism of which needs to be clarified. We preliminarily elucidate the mechanism of the TLRs/MyD88-PI 3 K/Akt signalling pathway in intestinal inflammation induced by plant proteins. The diets contained 60% fish meal (FM, controls), or had 45% of the fish meal protein replaced by soybean meal (SBM), peanut meal (PM), cottonseed meal (CSM) or cottonseed protein concentrate (CPC). After an 8-week feeding trial, fish were challenged by injection of Vibrio parahaemolyticus bacteria for 7 days until the fish stabilized. The results showed that the specific growth rate (SGR) of the FM group was higher than other groups. The SGR of the CPC group was higher than those of the SBM, PM and CSM groups. The catalase (CAT) contents in the serum of fish fed a plant protein diet were higher than in FM fish. The abundances of Rhodobacteraceae and Microbacteriaceae in the MI (mid intestine) were higher in the CPC group. The TLR-2 expressions in the MI and DI of plant protein-fed fish were up-regulated. The expressions of IL-6 in the PI and MI, of hepcidin and TLR-3 in the MI, and of TLR-3 in the DI, were all lower than those of fish fed FM. In the PI, MI and DI, the protein expressions of P-PI 3 K/T-PI 3 K in the SBM and PM groups were higher than in the FM group. After the challenge, the cumulative mortalities in the FM and CPC groups were lower than those of the SBM, PM and CSM groups. These results suggested that plant protein diets reduced antioxidant capacity and glycolipid metabolism, hindered the development of the intestine and reduced intestinal flora diversity. TLR-3 is involved in the immune regulation of the PI in CPC group, MI and DI in SBM, PM, CSM and CPC groups, while might be involved in the immune regulation of the PI in SBM, PM and CSM groups. Furthermore, PI 3 K/Akt signaling does not participate in the regulation of PI and MI in the CSM group, MI and DI in the CPC group., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

An 8-week feeding trial was conducted to investigate the effects of partial replacement of fish meal by soy protein concentrate (SPC) on the growth performance, immune responses, intestine morphology and relation gene expression of intestinal inflammation for juvenile hybrid grouper (Epinephelus fuscoguttatus ♀ × Epinephelus lanceolatus ♂) (initial weight 12.5 ± 0.00 g). Eight isonitrogenous and isolipidic diets (48.61% protein and 11.17% lipid) were formulated by replacing 0% (the control), 11%, 22%, 33%, 44%, 55%, 66%, and 77% of fish meal (FM) with SPC, respectively (the eight dietary be named FM, S11, S22, S33, S44, S55, S66, and S77, respectively). With the replacement level increased, the final body weight, weight gain ratio (WGR), specific growth rate (SGR), and survival rate of fish were significantly decreased (P < 0.05) compared with the group FM. By contrast, the feed conversion ratio (FCR) of fish was significantly increased (P < 0.05) when the replacement level up to 44%. Partial FM replacement by SPC (ranging from 11% to 77%) substantially reduced (P < 0.05) the serum total protein, albumin, and total cholesterol contents compared with the group FM. Liver total superoxide dismutase, glutathione peroxidase, catalase activities, and total antioxidant capacity showed the same trend of gradual increase first and then decrease. Their highest values were found in the replacement levels of 55%, 33%, 22%, and 55% and were significantly higher (P < 0.05) than the control group. The lowest malondialdehyde content was observed in group S77 and was significantly lower (P < 0.05) than that of the control group. The complements C3 and C4 contents of fish fed with experimental diets (replacement level ranged from 11% to 66%) were significantly higher (P < 0.05) than the group FM. The liver lysozyme activity of the control group was the lowest and was significantly lower than that of other dietary treatments (P < 0.05). Villus length and muscle thickness in the intestine of fish were significantly lower (P < 0.05) than other groups when the replacement level exceeded 44%. With dietary replacement levels increased, the TLR22, MyD88, p65, pro-inflammatory cytokines (IL-1β, TNF-α, IL-12P40 and INF-γ) and anti-inflammatory cytokines (TGF-β, IL-10, epinecidin, MHCIIβ and hepcidin) mRNA levels in the proximal intestine were significantly up-regulated (P < 0.05). The TLR22, MyD88, p65, pro-inflammatory cytokines (IL-1β, TNF-α, IL-12P40 and INF-γ) and anti-inflammatory cytokines (TGF-β, IL-10, MHCIIβ and hepcidin) mRNA levels in the mid intestine were significantly up-regulated (P < 0.05). The mRNA levels of TLR22, anti-inflammatory cytokines (IL-1β, TNF-α, IL-12P40, INF-γ) and anti-inflammatory cytokines (TGF-β, IL-10, epinecidin, MHCIIβ and hepcidin) in the distal intestine were significantly down-regulated (P < 0.05). The mRNA expression of MyD88 and p65 mRNA were showed a tend increased first and then decreased, and the highest values were observed in group S33 and S55 (P < 0.05), respectively. Based on the present work, the correlation between WGR and FM replacement level with SPC was described using the broken-line model, which estimated the optimum FM replacement to 37.23% for juvenile hybrid grouper dietary., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The present study was conducted to evaluate the influence of Glycyrrhiza uralensis (G. uralensis) extracts on the growth performance, histological structure, immune response and disease resistance against Flavobacterium columnare (F. columnare) of yellow catfish. Fish were fed with two different diets, i.e., basal diet as control group (CG) and diet containing G. uralensis extracts as experimental group (GG). After 60 days feeding, growth performance of GG fish was significantly improved, with increased WG and SGR but decreased FCR compared to CG fish. Fish were then challenged with F. columnare for two times, as fish showed rare mortality after the first infection. GG fish showed significantly lower cumulative mortality during F. cloumnare infection than CG fish after 21 days infection (dpi). Epithelial cell exfoliation and obvious cellular vacuolization in the skin and congestion of gill lamellae were detected in CG fish, while GG fish showed increased width of epidermis and mucous cells number in skin, and increased length of secondary lamina in gill. GG fish also exhibited higher enzyme activity of lysozyme in serum and mRNA expression of lysozyme in head kidney than CG fish at most time points post infection. G. uralensis extracts supplementation also induced earlier serum anti-oxidative responses, with increased superoxide dismutase activity and total antioxidant capacity in GG fish at 1 dpi. Compared to CG fish, GG fish showed increased expression level of genes involved in TLRs-NFκB signaling (TLR2, TLR3, TLR5, TLR9, Myd88, and p65NFκB), resulting in higher expression levels of pro-inflammatory cytokines (IL-1β and IL-8) in the head kidney post infection. However, these genes showed deviation in the gill of GG fish, which increased at some time points but decreased at other time points. Moreover, G. uralensis extracts supplementation also significantly unregulated the expression levels of IgM and IgD in head kidney, and the expression levels of IgM in the gill of yellow catfish, suggesting the elevated humoral immune response during F. columnare infection. All these results contributed to the elevated disease resistance ability against F. cloumnare infection of yellow catfish after dietary G. uralensis extracts supplementation., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

This study was conducted to investigate the effects of dietary n-3 highly unsaturated fatty acids (n-3 HUFA) on growth performance, non-specific immunity, expression of some immune-related genes and resistance to Vibrio harveyi in juvenile hybrid grouper (♀ Epinephelus fuscoguttatus × ♂ Epinephelus lanceolatu). Six isoproteic and isolipidic experimental diets were formulated with graded levels of n-3 HUFA (0.65, 1.00, 1.35, 1.70, 2.05 and 2.40% of dry matter, respectively), and the 0.65% group was used as control group. Each diet was randomly allocated to triplicate groups of fish in 1000 L fiberglass tank, and each tank was stocked with 40 fish (initial weight 12.06 ± 0.01 g) for 8 weeks. Results showed that feed conversion ratio (FCR), survival rate (SR), hepatosomatic index (HSI) and condition factor (CF) were all not significantly affected by dietary n-3 HUFA levels (P > 0.05). Weight gain (WG) and specific growth rate (SGR) in 1.35% group were significantly higher than those in 2.40% group (P < 0.05). Crude lipid of body in 1.00% group was significantly lower than that in 1.70% and 2.40% groups (P < 0.05). Liver and muscle fatty acid profiles reflected that of diets. Before challenge with Vibrio harveyi, the activity of serum superoxide dismutase (SOD), catalase (CAT) and content of complement 3 (C3) in 1.35% and 1.70% groups significantly higher than those of control group (P < 0.05). After challenge with Vibrio harveyi, serum CAT, glutathione peroxidase (GSH-PX), lysozyme (LZM) and C3 all increased sharply, while SOD showed the opposite trend. Before challenge with Vibrio harveyi, the expression levels of intestine toll-like receptor 22 (TLR22) and myeloid differentiation factor 88 (MyD88) mRNA in 2.40% group were significantly increased, and the expression levels of tumour necrosis factor α (TNF-α) and interleukin 1β (IL-1β) mRNA in 2.05% group were significantly higher than those in 1.00% and 1.35% groups (P < 0.05). In addition, the TLR22 and IL-1β mRNA levels in kidney of 1.70% group were significantly lower than those in control group (P < 0.05). After challenge with Vibrio harveyi, the expression level of MyD88 mRNA in intestine of 1.35% group was significantly higher than that in 1.00% group and from 1.70% to 2.40% groups (P < 0.05), while TNF-α and IL-1β obtained minimum values in 1.70% group. In the kidney, the interleukin 10 (IL10) mRNA expression was significantly higher in 1.70% group than that in other groups, while the IL-1β expression in 1.70% group was on the contrary and significantly lower than that in 2.40% group (P < 0.05). Results of this study suggested that moderate dietary n-3 HUFA (1.47%-1.70% HUFA) could improve the growth performance, non-specific immunity and inhibit the inflammatory response of hybrid grouper., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

In order to illustrate the immunometabolic changes of fish during bacterial infection, grass carp (Ctenopharyngodon idellus) was injected with Flavobacteriumcolumnare(F.columnare) and then the immune response, nutrient metabolism and related signaling pathways were assayed from 6 h post injection (hpi) to 7 days post injection (dpi). After F.columnare injection, gill lamellae showed obvious fusion and higher mRNA expression levels of pro-inflammatory cytokines. The mRNA expression levels of TNF-α, IL-1β and IL-8 in the head kidney were also significantly upregulated at 6 hpi and 3 dpi. Moreover, the expression of IgZ in the gill was significantly upregulated at 3 dpi and 7 dpi, while the expression of IgM in the head kidney was significantly upregulated at 1 dpi and 3 dpi after F.columnare injection. During bacterial infection, the systematic nutrient metabolism was also significantly affected. Hepatic glycolysis, indicated by GK mRNA expression and PK activity, was significantly upregulated at 1 dpi, while glucogenesis, indicated by PEPCK mRNA expression and enzyme activity, was significantly increased at later time, which resulted in the decreased hepatic glycogen content at 1dpi but increased glycogen content at 7 dpi in the experimental group. LPL, which catalyzed the lipid catabolism, showed decreased mRNA expression and enzyme activity at 6 hpi, while ACC, which was rate-limiting of FA synthesis, was significantly increased at 6 hpi, 3 dpi and 7 dpi. During this process, the nutrient sensing signaling was also significantly affected. TOR signaling in grass carp was significantly activated while ERK signaling was significantly inhibited after F.columnare infection, both of which might function as the sensor and regulator of fish immunometabolic changes., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Cottonseed protein concentrate (CPC) has similar amino acid composition compared with fish meal, and has the characteristics of low gossypol and low toxicity. The present study was conducted to investigate the growth performance, antioxidant capacity and different intestinal segments immune responses of hybrid grouper to replacement dietary fish meal ofCPC. Six iso-nitrogenous (50% crude protein) and iso-lipidic (10% crude lipid) diets were formulated: a reference diet (FM) containing 60% fishmeal and five experimental diets (12%, 24%, 36%, 48 and 60%) in which fishmeal protein was substituted at different levels by CPC to feed fish (initial body weight: 11 ± 0.23 g) for 8 weeks. Thena challenge test with injection of Vibrio parahaemolyticus was conducted for 7 days until the fish stabilized. The results showed that specific growth rate (SGR) was the highest with 24% replacement level and feed conversion ratio (FCR)was significantly increased when the replacement level reached 48% (P < 0.05). The content of malonaldehyde (MDA) in the serum was significantly increased when the replacement level reached 36% (P < 0.05). The plica height in the proximal, mid and distal intestine were significantly decreased with the replacement level up to 48% (P < 0.05). Hepatic fat deposition wasaggravatedwhen the replacement level reached 36% (P < 0.05). The expression of IL-6, TNF-α, and IL-1β mRNAs were significantly up-regulated (P < 0.05). The hepcidin mRNA expression was significantly down-regulated (P < 0.05). In proximal intestine (PI) and mid intestine (MI), IFN-γ mRNA expression was significantly up-regulated (P < 0.05). These results suggested that the CPC decreased hybrid grouper growth performance and inflammation function, and different inflammation function responses in PI,MI, and distal intestine (DI) were mediated partly by the TLR-2/MyD88 signaling pathway. According to the analysis of specific growth rate, the dietary optimum replacement level and maximum replacement level were estimated to be 17% and 34%, respectively., (Copyright © 2018 Elsevier Ltd. All rights reserved.)