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Four isonitrogenous and isolipidic diets containing fresh fish oil (peroxide value, POV: 7.2 meq kg−1, diet FR) and three degrees of oxidized fish oil (POV: 155, 275 and 564 meq kg−1, diet OX155, OX275 and OX564, respectively) were formulated to investigate the effects of dietary oxidized fish oil on growth performance, body composition, antioxidant defense system and mitochondrial function of juvenile largemouth bass, Micropterus salmoides. After a 12-week feeding trial, fish fed the OX155 obtained significantly higher (P

The present study investigated the potential mechanisms of astaxanthin in the regulation of gastrointestinal immunity and retinal mitochondrial function of golden pompano (Trachinotus ovatus). Triplicate groups of juvenile T. ovatus (mean initial weight: 6.03 ± 0.01 g) were fed one of six diets (D1, D2, D3, D4, D5, and D6) for 8 weeks, with each diet containing various concentrations of astaxanthin (0, 0.0005, 0.001, 0.005, 0.01, or 0.1%, respectively). Growth performance of fish fed the D2–D5 diets was higher than that of fish fed the D1 diet; however, growth performance and survival of fish deteriorated sharply in fish fed the D6 diet. Gut villus in fish fed the D2–D5 diets were significantly longer and wider than that of fish fed the D6 diet. Feeding with D2–D5 diets led to increased abundance of Bacillus, Pseudomonas, Oceanobacillus, Lactococcus, Halomonas, Lactobacillus, and Psychrobacter while abundance of Vibrio and Bacterium decreased. Additionally, feeding with the D6 diet resulted in a sharp decline in Pseudomonas and Lactobacillus abundance and a sharp increase in Vibrio abundance. A low dissolved oxygen environment (DO, 1.08 mg/L) was conducted for 10 h after the rearing trial. No fish mortality was observed for any of the diet treatments. Lysozyme (LZY) activity in fish fed the D6 diet decreased sharply and was significantly lower than that in other groups. ROS production also decreased sharply in fish fed the D6 diet. Moreover, the conjunctiva and sclera in the fish fed the D6 diet were indistinguishable. Suitable dietary astaxanthin supplementation levels (0.005–0.1%) exerting a neuroprotective effect from low dissolved oxygen environments is due to up-regulated expression of anti-apoptotic factors, such as phosphorylated Bcl-2-associated death promoter (pBAD), phosphorylated glycogen synthase kinase-3β (pGSK-3β), Bcl-2 extra large (Bcl-xL), and down-regulated expression of Bcl-2-associated X protein (Bax) pro-apoptotic factor in retinas. Furthermore, suitable dietary astaxanthin levels (0.0005–0.01%) suppressed up-regulation of critical mitochondrial components, such as peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α), mitochondrial transcription factor A (TFAM), and mitochondrial DNA (mtDNA), while excessive astaxanthin supplementation produces the opposite effect. In brief, high-dose astaxanthin arouses and aggravates low dissolved oxygen-induced inflammation, oxidative stress, intestinal disorder, retinal apoptosis, and retinal mitochondrial dysfunction in T. ovatus. Second-degree polynomial regression of WG indicated that the optimum dietary astaxanthin for juvenile T. ovatus is 0.049%.

Two trials were conducted to determine the effects of dietary Forsythia suspensa extract (FSE) on shrimp, Penaeus monodon, first on growth performance, second on the immune response and immune related gene expression of shrimp. In trial 1, shrimp (mean initial wet weight about 3.02 g) were fed with five diets containing 0% (basal diet), 0.01%, 0.02%, 0.04% and 0.06% FSE in triplicate for 60 days. Growth performance (final body wet weight, FBW; weight gain, WG; biomass gain, BG) of shrimp fed FSE diets were higher (P 0.05). The antioxidant capacity (total antioxidant status, TAS; glutathione peroxidase, GSH-Px) appears in the trend of firstly increasing then decreasing with the increasing of dietary FSE levels. The highest value of TAS and GSH-Px were found in shrimp fed 0.02% FSE diet and were significantly higher than that of shrimp fed the basal and 0.06% FSE diets (P 0.05). In trial 2, a pathogenic strain of Vibrio parahaemolyticus 3HP (VP3HP) injection challenge test was conducted for 6-day after the rearing trial and shrimp survival were also compared among treatments. Survival of shrimp fed diets supplemented with 0.01%–0.02% FSE were higher than that of shrimp fed the basal and 0.06% FSE diets (P 0.05). The molecular gene expression profile of Hsp 70 mRNA was increased while HIF-1α mRNA was decreased when compared to trial 1. In conclusion, results suggested that dietary intake containing FSE could enhance the growth performance and antioxidant capacity of P. monodon and furthermore reduce oxidative stress and immune depression challenged by a pathogenic strain of Vibrio parahaemolyticus stress. Considering the effect of FSE on both growth performance and immune response of P. monodon, the level of FSE supplemented in the diet should be between 0.01% and 0.02%.

A feeding experiment was conducted to determine the effects of Schizochytrium sp. on growth performance, antioxidant capacity and non-specific immunity in golden pompano (Trachinotus ovatus).Two diets were formulated with or without Schizochytrium sp. supplemented (D1:0% and D2: 3%) to feed fish for 8 weeks. Results showed that growth performance, feed intake and survival rate increased significantly with Schizochytrium sp. supplemented (P 0.05). Feed coefficient rate (FCR) of golden pompano fed the diet supplemented with Schizochytrium sp. was significantly lower than that of fish fed the control diet (P 0.05). No significant differences were found in antioxidant capacity both in transcriptional level, including nclear factor erythroid-2-related factor-2 (Nrf2), Kelch-like-ECH-associated protein (keap1), catalase (CAT), glutathione peroxidase (GSH-PX) and heme oxygenase 1 (HO-1) and enzyme activity, such as total antioxidant capacity (T-AOC), malondialdehyde (MDA) and superoxide dismutase (SOD) (P 0.05). Gut amylase and lipase were significantly higher in dietary Schizochytrium sp. supplemented treatment than that in control group (P 0.05). The relative peroxisome proliferator-activated receptor-α (PPARα) expression level in liver was significantly higher in Schizochytrium sp supplemented treatment than that in control one (P 0.05). The mRNA expression of myeloid differentiation factor 88 (MyD88), IL-1R-associated kinases 4 (IRAK4), interferon regulating Factor 3 (IRF3), interferon regulating Factor 3(IRF7) and heat shock protein 70 (HSP70) were significantly lower in Schizochytrium sp. supplemented treatment than that in control one (P 0.05). In Schizochytrium sp. supplemented diet, golden pompano had significantly longer villi length than that in control diet (P 0.05); muscle thickness in Schizochytrium sp. supplemented diet was thicker than that in control one (P 0.05) and there were more goblet cells in Schizochytrium sp. treatment (P 0.05). After the rearing trial, an air exposure trial was conducted. Results showed that the air-exposure mortality (AEM) and mRNA expression level of Nrf2, keap1, CAT, GSH-PX and HO-1 showed no significant difference (P 0.05). These results indicated that dietary Schizochytrium sp. improved the growth performance and non-specific immunity of golden pompano while made no difference to antioxidant capacity.

Heme oxygenase-1(HO-1) is a stress-inducible enzyme that mediates antioxidative and cytoprotective effects to maintain cellular redox homeostasis. In the present study, the full sequence of HO-1 was cloned from golden pompano(Trachinotus ovatus) by RT-PCR and RACE-PCR. The full cDNA sequence of HO-1 was 1349 bp in length which comprised of a 726 bp open reading frame (ORF) preceded by 262 bp 5′-untranslated region (UTR), and followed by a 360 bp 3′UTR, encoding 241 amino acid residues. Phylogenetic analysis revealed that HO-1 showed highest similarity to that of Takifugu rubripes. Tissue distribution analysis showed that the expression level of HO-1 was relatively high in heart, liver and spleen. A trial was conducted to investigate the response of Nrf2/HO-1 signaling pathway to oxidative stress induced by copper. The results showed that mRNA expression of NF-E2-related nuclear factor2 (Nrf2), Kelch-like-ECH-associated protein1 (keap1), superoxide dismutase (SOD), catalase (CAT), HO-1, NAD(P)H quinone oxidoreductase 1 (NQO1) and Glutathione peroxidase (GSH-PX) all significantly increased in copper treated group than that in the control group. This work provides new insight into the molecular mechanism underlying the Nrf2/HO-1 pathway in oxidative response in T. ovatus.

This study was conducted to elucidate the effects of dietary mixed probiotics on growth, non-specific immunity, intestinal morphology and microbiota of juvenile pacific white shrimp, Litopenaeus vannamei. Juvenile shrimp (initial body weight 1.21 ± 0.01 g) were fed diets containing graded probiotics (F1: 0 mg/kg probiotics; F2: 1000 mg/kg probiotics; F3: 2000 mg/kg probiotics; F4: 4000 mg/kg compound probiotics; F5: 6000 mg/kg probiotics; F6: 8000 mg/kg probiotics) for 8 weeks. The result of this trial showed that the growth performance (SGR, WG, FBW) of shrimp fed diets containing probiotics (F2∼F6) were significantly higher than that of shrimp fed diet without supplemental probiotics (F1) (P 0.05), and the highest values of the growth performance (SGR, WG, FBW) and lowest FCR were found in shrimp fed the diet containing 2000 mg/kg probiotics. Total antioxidant capacity of shrimp fed diet F2 and F3 were significantly higher than that of shrimp fed the basal diets (P 0.05). Superoxide dismutase in F4 treatment was significantly higher than that of basal treatment (P 0.05). Catalase of shrimp in all probiotics supplemented (F2∼F6) treatments were significantly higher than that of the control one (F1) (P 0.05). Malondialdehyde in F5 groups was significantly lower than that of F1 groups (P 0.05). Alkline phosphatase and acid phosphatase in F3 treatments were significantly higher than those of the basal one (P 0.05). Lysozyme of shrimp fed F2∼F6 were significantly higher than that of shrimp fed F1 diet (P 0.05). The lipase and amylase activities in 2000 mg/kg probiotics groups showed the highest activities and were significantly higher than that of control one (P 0.05). Intestinal villi height in F3∼F6 treatments were significantly higher than that of control one (P 0.05). Alpha diversity indices including observed species, chao1, ACE and shannon indices showed that F2 and F3 groups had higher microbial diversity in their intestines, both richness and evenness. PCA plot showed that there was a clear shift of F2 and F3 groups from the control groups in microbial community structure. The dominant phyla in pacific white shrimp are proteobacteria, bacteroidetes and actinobacteria, the dominant genus were algoriphagus and vibrio. As the probiotics increased, the gemmatimonadetes, acidobacteria, deltaproteobacteria and xanthomonadales firstly increased and then decreased, with the highest content in F2 group, which was no significant difference to F3 group (P 0.05) while significantly higher than other groups (P 0.05). In conclusion, the supplement of mixed species probiotics can promote growth performance, enhance the non-specific immunity, influence the microbiota of the pacific white shrimps and the recommended optimum dosage in diet of Litopenaeus vannamei was 2000 mg/kg.

The study was conducted to compare and evaluate effects of four different macro-algaes on growth, immune response, and intestinal microbiota of Litopenaeus vannamei. In the rearing trial 1, shrimp were fed five diets containing four sources of macro-algaes for 8 weeks, named D1 (without macro-algae), D2 (Porphyra haitanensis), D3 (Undaria pinnatifida), D4 (Saccharina japonica), and D5 (Gracilaria lemaneiformis), respectively. Growth performance of shrimp in D5 diet was significantly higher than that of shrimp fed the control and D4 diet (P < 0.05); however, there is no significant difference among D2, D3, and D5 diets (P > 0.05). Apparent digestibility coefficients of dry matter from the D2, D3, and D5 diets were significantly higher than that from the control and D4 diets (P < 0.05). Supplementary macro-algaes enhanced hepatopancreas immunity through positively increasing total antioxidant status (TAS) and prophenoloxidase activity (ProPO), as well as up-regulating the hepatopancreas RNA expression of ProPO and IκBα and down-regulating the expression of transforming growth factor β. Furthermore, dietary macro-algaes modified intestinal microbiota of L. vannamei, boosting the relative abundance of beneficial bacterial such as Bacteroidetes, Firmicutes, and Bacillaceae, and decreasing those detrimental bacterial such as Gammaproteobacteria and Vibrionaceae. In the white spot syndrome virus (WSSV) challenge trial, shrimps were injected for 6-day after the rearing trial. On the fourth day, shrimp death started to occur, and the mortality in D2, D3, and D5 diets was significantly lower than that in control and SJ diets during 4–6 challenged days (P < 0.05). Dietary macro-algaes ameliorated hepatopancreas damage in L. vannamei by increasing TAS and ProPO activities and decreasing SOD activity, inhibiting the lipid peroxidation (malondialdehyde), as well as regulating the immune-related genes expression. Taken together, dietary macro-algaes availably relieved enterohepatic oxidative damage by improving antioxidant ability and immunity and regulated intestinal microbiota in L. vannamei. These results indicated that G. lemaneiformis is the most suitable macro-algae and then followed by U. pinnatifida and P. haitanensis as the feed ingredient for L. vannamei.

Filamentous microalga Tribonema sp. contains multiple bioactive compounds, such as eicosapentaenoic acid (EPA), palmitoleic acid and chrysolaminarin. Tribonema sp. is potentially a nature and safe ingredient in aquatic feed. Therefore, 6-week feeding experiment was conducted to investigate the effects of Tribonema sp. on growth performance, antioxidant capacity, immunity and hepatic health of Trachinotus ovatus. Three isonitrogenous and isolipidic diets (TS0, TS1 and TS5) containing 0% (control group), 1% and 5% Tribonema sp. were formulated, respectively. Results indicated that T. ovatus fed with TS5 diet significantly improved the growth performance by enhancing digestive enzyme activities and up-regulating the expression of growth hormone (GH) and insulin-like growth factor (IGF-I). T. ovatus fed with TS5 diet also significantly facilitated the antioxidant capacity through activating the Nrf2-ARE signal pathway and increasing antioxidant enzyme activities. Meanwhile, TS5 diet significantly promoted liver health by upregulating the expression of anti-inflammatory cytokines and downregulating the expression of pro-inflammatory cytokines. Furthermore, TS5 diet also upregulated the expression levels of non-specific immune related genes, including complement 4 (C4), c-type lysozyme (C-Lyz) and heat shock protein 70 (HSP70). In conclusion, Tribonema sp. can be used as feed ingredients to increase growth performance, antioxidant capacity, immunity and improve hepatic health in T. ovatus.

Carbohydrates are the cheapest source of dietary energy for fish. Utilization of carbohydrates in feed is beneficial to sparing protein consumption as energy source and saving feed cost. Therefore, 8-week feeding experiment was conducted to investigate the effects of starch level on growth performance, antioxidant capacity, serum biochemical parameters, intestinal morphology and intestinal microbiota of Trachinotus ovatus. Six isonitrogenous and isolipidic diets (D1, D2, D3, D4, D5 and D6) containing 0%, 5%, 10%, 15%, 20% and 25% corn starch were formulated, respectively. Each diet was randomly assigned to triplicate groups of fish (initial body weight 11.84 g) fed twice daily to apparent satiation. Results showed that percent weight gain, specific growth ratio, hepatosomatic index, total antioxidation capacity and glutathione content of fish fed with D6 diet were the highest among all experimental treatments. Feed conversion rate was significantly lower in fish fed with D5 and D6 diets, than in fish fed with D1-D4 diets. No significant differences were found in the survival rate, viscerasomatic index, malondialdehyde and serum triglyceride contents among all diet treatments. The superoxide dismutase activity of T. ovatus fed with D3-D6 diets were relatively higher than those fed with D1 and D2 diets. Fish fed with D3 diet showed the highest value of serum total cholesterol. High-density lipoprotein cholesterol / low-density lipoprotein cholesterol ratio of fish fed with D1 and D6 diets were relatively higher than those fed with D2-D5 diets. No significant pathological changes in the foregut were observed among all diet treatments. Dietary starch level lead to alterations in the intestinal microbiota in T. ovatus. D2-D5 dietary treatments increased the abundance of harmful bacteria such as Vibrio, Photobacterium, Mycoplasma. D1 and D6 dietary treatments had similar intestinal microbiota composition. In conclusion, 25% starch level was beneficial to the growth and health of T. ovatus.

p65 is an important component of NF-κB signaling pathways. However, information about p65 subunit in golden pompano (Trachinotus ovatus) is quiet limit. Thus, the full length of p65 subunit was cloned from T. ovatus in this study. The full-length cDNA sequence was 3162 bp in length and comprised of a 1886 bp open reading frame (ORF) preceded by 153 bp 5′-untranslated region (UTR), and followed by a 1143 bp 3′UTR. The p65 of T. ovatus contains a conserved N-terminal REL-homology domain (RHD) with 273 amino acids. The phylogenetic tree showed that p65 in T. ovatus was clustered in the clade of that in marine fish. mRNA expression of p65 was detected in 12 different tissues. The results showed that expression of p65 in liver was higher than that in other tissues (P 0.05). After 8-weeks feeding, the hepatic expression level of p65 and IL1β in fish fed diet with high fat showed significant difference with that in control diet (P

Two trials were conducted to determine the effects of dietary macroalgae Porphyra haitanensis on growth, immunity and intestinal microbiota of Litopenaeus vannamei. In trial 1, shrimp (mean initial wet weight about 0.64 g) were fed with seven diets (P0, P1, P2, P3, P4, P5 and P6) containing 0% (basal diet), 1%, 2%, 3%, 4%, 5% and 6% P. haitanensis in triplicate for 60 days. Growth performance (weight gain, WG; specific growth rate, SGR) of shrimp fed the P4 diet were significantly higher than that of shrimp fed P0, P5 and P6 diets (P 0.05) but without significant differences with shrimp fed P1-P3 diets (P 0.05). Hepatopancreas phenoloxidase (PO) activity of shrimp fed the P. haitanensis containing diets was significantly higher than that of shrimp fed the basal diet (P0) (P 0.05). Total haemocyte count (THC) of shrimp fed basal diet (P0) was significantly lower than that of shrimp fed diets containing P. haitanensis. Our results declared that dietary P. haitanensis supplementation increases the abundance of beneficial bacterials such as Nitrosopumilus, Marinobacter or Bifidobacterium and reduces the abundance of harmful bacterias such as Vibrio, and especially pronounced in P4 diet treatment. In trial 2, a WSSV injection challenge test was conducted for 7-day after the rearing trial and shrimp survival was also compared among treatments. A sudden shrimp death was found from the 4th day, and values of survival of shrimp fed the P3-P4 diets were higher than that of shrimp fed other diets during 4-7 days challenge test. The immune response in trial 2 were characterized by higher superoxide dismutase activity (SOD) and PO activities, lower THC and higher HCT compared to levels found in trial 1. In conclusion, suitable dietary P. haitanensis could enhance the growth performance, antioxidant capacity and alter total bacterial numbers or microbial diversity of L. vannamei and furthermore reduce oxidative stress and immune depression challenged by WSSV injection stress, and the level of P. haitanensis supplemented in the diet should be between 2.51% and 3.14%.

Two trials were conducted to determine the effects of dietary Forsythia suspensa extract (FSE) on shrimp, Penaeus monodon, first on growth performance, second on the immune response and immune related gene expression of shrimp. In trial 1, shrimp (mean initial wet weight about 3.02 g) were fed with five diets containing 0% (basal diet), 0.01%, 0.02%, 0.04% and 0.06% FSE in triplicate for 60 days. Growth performance (final body wet weight, FBW; weight gain, WG; biomass gain, BG) of shrimp fed FSE diets were higher (P 0.05) than that of shrimp fed the basal diet. The survival among all the diets treatments were above 90% and no significant difference was revealed among them (P 0.05). The antioxidant capacity (total antioxidant status, TAS; glutathione peroxidase, GSH-Px) appears in the trend of firstly increasing then decreasing with the increasing of dietary FSE levels. The highest value of TAS and GSH-Px were found in shrimp fed 0.02% FSE diet and were significantly higher than that of shrimp fed the basal and 0.06% FSE diets (P 0.05). Hepatopancreas malondialdehyde (MDA) of shrimp fed FSE diets were lower (P 0.05) than that of shrimp fed the basal diet. Total haemocyte count of shrimp fed the basal diet was lower (P 0.05) than that of shrimp fed FSE diets. Haemolymph clotting time of shrimp had the opposite trend with the total haemocyte count of shrimp. No significant differences were found in haemolymph biomarkers of intestinal permeability (endotoxin and diamine oxidase) and in molecular gene expression profiles of heat shock protein 70 (Hsp 70) mRNA and hypoxia inducible factor-1α (HIF-1α) mRNA in haemolymph of shrimp among all diet treatments (P 0.05). In trial 2, a pathogenic strain of Vibrio parahaemolyticus 3HP (VP