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Zn is an important trace element involved in various biochemical processes in aquatic species. An 8-week rearing trial was thus conducted to investigate the effects of Zn on juvenile largemouth bass (Micropterus salmoides) by feeding seven diets, respectively, supplemented with no Zn (Con), 60 and 120 mg/kg inorganic Zn (Sul60 and Sul120), and 30, 60, 90 and 120 mg/kg organic Zn (Bio30, Bio60, Bio90 and Bio120). Sul120 and Bio120 groups showed significantly higher weight gain and specific growth rate than Con group, with Bio60 group obtaining the lowest viscerosomatic index and hepatosomatic index. 60 or 90 mg/kg organic Zn significantly facilitated whole body Zn retention. Up-regulation of hepatic superoxide dismutase, glutathione peroxidase and catalase activities and decline of malondialdehyde contents indicated augmented antioxidant capacities by organic Zn. Zn treatment also lowered plasma aminotransferase levels while promoting acid phosphatase activity and hepatic transcription levels of alp1, acp1 and lyz-c than deprivation of Zn. The alterations in whole body and liver crude lipid and plasma TAG contents illustrated the regulatory effect of Zn on lipid metabolism, which could be possibly attributed to the changes in hepatic expressions of acc1, pparγ, atgl and cpt1. These findings demonstrated the capabilities of Zn in potentiating growth and morphological performance, antioxidant capacity, immunity as well as regulating lipid metabolism in M. salmoides. Organic Zn could perform comparable effects at same or lower supplementation levels than inorganic Zn, suggesting its higher efficiency. 60 mg/kg supplementation of organic Zn could effectively cover the requirements of M. salmoides.

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%.

The present study was conducted to evaluate the effect of replacing fishmeal (FM) with Rhodobacter sphaeroides protein on growth performance, intestinal morphology and antioxidant capability of Pacific white shrimp (Litopenaeus vannamei) in an eight-week feeding experiment. FM protein of a FM-based control diet (FM20) was replaced with 0 (FM20), 4 (FM16), 8 (FM12), 12 (FM8), 16 (FM4), and 20% (FM0) by Rhodobacter sphaeroides protein to formulate six experimental diets. Compared with control group, the shrimp fed 4% (FM16) and 8% (FM12) Rhodobacter sphaeroides protein gained higher survival rate and specific growth rate (SGR). There were no significant differences in MDA content of hepatopancreases and crude protein in whole body, while crude lipid was increased significantly in shrimp fed with Rhodobacter sphaeroides protein. In addition, there was no negative impact on the intestinal morphology of shrimp by FM replacement with Rhodobacter sphaeroides protein. The challenge test with low salt stress showed that the survival rate of shrimp fed with Rhodobacter sphaeroides protein were not significantly different from that of shrimp fed with whole fishmeal. Furthermore, higher T-AOC and GSH-PX activities of hepatopancreases of shrimp were observed in Rhodobacter sphaeroides protein after low salt stress. Moreover, compared with the control group, substitution of Rhodobacter sphaeroides significantly improved the resistance of L. vannamei against the stress of acute low salinity, as indicated by higher expression levels of SOD, Relish and HSP70 and lower expression levels of Caspase-3. Our findings suggested that Rhodobacter sphaeroides protein, has improved growth performance and maintained the intestinal tract healthy, and enhanced antioxidant competence and immunity of L. vannamei and could serve as novel FM replacement in shrimp feed that helps shrimp to overcome low salt challenge.

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.

Bile acid (BA) has been reported to improve growth performance and play an important role in lipid metabolism of fish. Five diets were formulated to investigate the effects of dietary bile acid (chenodeoxycholic acid) supplementation on growth performance, antioxidant capacity, lipid metabolism and intestinal health of juvenile largemouth bass (Micropterus salmoides). Fish (18.35 ± 0.05 g) were randomly fed five diets: the positive control diet (10.87% lipid, C), high fat diet (18.08% lipid, HF), and HF diets supplemented with 300, 600 and 900 mg/kg chenodeoxycholic acid (HFC1, HFC2 and HFC3, respectively). After 9 weeks of feeding experiment, the weight gain (WG) and special growth rate (SGR) were significantly lower in the fish fed diet HF compared with those fed diet C (P 0.05). Viscerosomatic index (VSI) and intraperitoneal fat ratio (IPF) were significantly higher in fish fed high fat diets than those fed the control diet (P 0.05), while the crude lipid of muscle significantly decreased in HFC2 group (P

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