The hybrid sturgeon (HS, Acipenser baerii Brandt ♀ × A. schrenckii Brandt ♂) was compared with its parental varieties (Siberian sturgeon (SS) and Amur sturgeon (AS)) to evaluate muscle quality differences. Three sturgeon species were bred from the same batch, reared under identical conditions until three years of age, and then male fish from each species (AS, 3.2 ± 0.18 kg; SS, 2.5 ± 0.14 kg; HS, 3.5 ± 0.21 kg) were sampled for analysis of muscle nutritional composition, texture, microstructure, and metabolomics. Results showed no significant differences in proximate composition, hydrolyzed amino acids, pH, or water-holding capacity among the three groups. However, HS exhibited higher gumminess and chewiness than both parent species, as well as greater hardness and springiness compared with the SS. Muscle fiber density was higher in HS than in the AS, but no significant difference was observed between HS and SS. Levels of free amino acids (Val, Ile, Ala) were lower in HS than in AS. In terms of fatty acid profiles, HS showed elevated polyunsaturated fatty acids compared with SS, resembling the pattern observed in AS. Muscle color of HS was similar to that of SS, whereas its a* value differed from those of AS. Metabolomics identified differential metabolites (GABA, D-glucosaminic acid, AP4) enriched in pathways such as ABC transporters, protein digestion and absorption, and amino acid metabolism. Overall, HS combines improved texture traits with meat quality attributes resembling SS (muscle color, free amino acids) and AS (polyunsaturated fatty acids). These characteristics suggest that HS possesses a distinctive combination of meat quality traits.

Sturgeons, ancient fish and the source of caviar, are ecologically and economically vital in aquaculture. To enhance feed efficiency, the use of cost-effective non-protein ingredients such as soybean oil and starch has gained growing attention. This study investigated the effects of oil sources and starch levels on growth, lipid metabolism, and inflammation in Siberian sturgeon (Acipenser baerii). Four isonitrogenous and isolipidic diets were formulated: fish oil diet with low starch level (FOLS), soybean oil diet with low starch level (SOLS), fish oil diet with high starch level (FOHS), and soybean oil diet with high starch level (SOHS). A total of 240 fish (initial weight: 182.87 ± 0.24 g) were used in a 10-week feeding trial. They were randomly assigned to 12 tanks, with three replicates per diet. Results showed that oil source had no significant effect on growth performance (P > 0.05), but high starch significantly reduced final body weight, weight gain rate, and specific growth rate (P < 0.05). Both soybean oil and high starch independently increased feeding rate and feed conversion ratio (P < 0.05), with their interaction further reducing feed efficiency (P < 0.05). High starch diets disrupted lipid metabolism. Specifically, they elevated hepatosomatic index, serum triglycerides (TG), total cholesterol (TC), and low-density lipoprotein cholesterol (P < 0.05), along with increased expression of hepatic genes related to fatty acid β-oxidation (pparα, P = 0.001). Soybean oil also promoted fatty acid β-oxidation (pparα and cpt1α, P < 0.05), and in combination with high starch, enhanced lipolysis (lpl, P = 0.042). Meanwhile, high starch upregulated the expression of pro-inflammatory gene (il1β, P = 0.020). The mRNA expression results indicated that the soybean oil-high starch combination further aggravated inflammation alongside enhanced fatty acid oxidation, ultimately impairing growth. A principal component analysis (PCA) analysis of the lipidome showed that the serum lipid profile was significantly affected by the oil source (P = 0.004). Seven metabolites were identified as commonly differentially abundant. Notably, phosphatidylethanolamine [PE (18:0_20:4) and PE (18:0_18:1)] and ceramide phosphate [CerP (d39:2)] were positively correlated with levels of TG, TC, and the expression of β-oxidation and inflammatory genes (P < 0.05), suggesting their potential key roles in lipid-inflammatory dysregulation. In conclusion, dietary soybean oil and high starch interact to modulate serum lipid molecules, enhance fatty acid β-oxidation and inflammation, reduce feed efficiency, and suppress growth. Therefore, careful regulation of starch levels is essential when substituting fish oil with soybean oil in sturgeon aquafeed formulations.

IntroductionKoi herpesvirus (KHV or CyHV-3) causes a highly contagious and lethal disease in common carp and koi, resulting in substantial economic losses in global aquaculture. Rapid point-of-care testing (POCT) of KHV is critical for curbing its spread and preventing outbreaks. However, conventional diagnostic approaches, such as TaqMan quantitative PCR (qPCR), require professional personnel and specialized equipment, limiting their on-site applicability.MethodsA rapid visual POCT assay was developed by combing loop-mediated isothermal amplification (LAMP) with non-invasive mucus swab sampling. Two optimized release solutions enabled one-step nucleic acid preparation within 5 min. Among five primer sets designed, the optimal set targeting the thymidine kinase (TK) gene was selected for isothermal amplification at 65 °C for 60 min. The assay was further adapted for naked-eye result interpretation using a pH-sensitive indicatior dye.ResultsThe assay demonstrated a detection limit of 21.42 copies/μL, with a 95% confidence interval of 14.88—41.83 copies/μL. No cross-reactivity was observed with seven common fish pathogens. Comparative evaluation with TaqMan qPCR using parallel clinical specimens yielded 100% concordant results. The total detection time was 65 min, enabling the POCT implementation across diverse scenarios.DiscussionThis non-invasive, visual LAMP-based POCT platform provides a sensitive, specific and equipment-free diagnostic strategy for KHV detection, facilitating timely disease surveillance, outbreak control management, and aquaculture biosecurity.

Background/Objectives: Aeromonas veronii is a significant pathogen affecting aquatic animals and has the potential to infect humans. Vaccination remains the most effective strategy for preventing infections caused by this bacterial strain. Methods: This study aimed to validate the efficacy of bacterial ghosts as an oral vaccine by administering them to Cyprinus carpio and evaluating the resultant innate and acquired immune responses. Following immunization, the vaccinated Cyprinus carpio were exposed to a lethal dose of the wild-type bacterial strain to assess survival rates and relative protection efficiency. Results: Oral vaccination with bacterial ghosts led to the significant enhancement of lysozyme (LZM) and myeloperoxidase (MPO) activity in koi serum. It also resulted in the upregulation of cytokines, such as IL-2 and TNF-α, as well as an increase in both systemic (IgM) and mucosal (IgZs) antibody responses. The immunized group demonstrated reduced cumulative mortality following bacterial challenge. The relative percent survival in the vaccinated group reached as high as 87.50%. Conclusions: The oral immunization of Cyprinus carpio with A. veronii-derived bacterial ghosts confers substantial immune protection, providing a foundational basis for the development of novel vaccines against A. veronii.

To systematically evaluate FB’s effects on tilapia muscle quality, two distinct experimental phases are designed, the crispy texture development phase (0–16 weeks) and the crispy texture retention phase (17–24 weeks), which can determine the minimum faba bean (FB) feeding duration required to achieve optimal textural modification and can assess the persistence of improved textural properties following FB withdrawal, respectively. The results demonstrated that a 60% FB inclusion diet administered for 16 weeks did not adversely affect tilapia growth performance. Significant improvements in textural parameters, including hardness, springiness, chewiness, and shear force, were observed in FB-fed tilapia as early as 8 weeks, with these enhancements being maintained throughout the 16-week feeding period. These superior textural characteristics persisted during the subsequent retention phase following FB withdrawal. Microstructural analysis revealed that the 60% FB diet significantly enhanced muscle-fiber density while reducing fiber diameter in tilapia during the 8–16 week feeding period. These microstructural modifications persisted throughout the texture retention phase, maintaining significant differences compared to the control group. Serological analysis demonstrated the FB group elevated Superoxide dismutase (SOD) activity and reduced malondialdehyde (MDA) levels at 4 weeks, though these differences normalized thereafter. qRT-PCR showed the 60% FB clearly increased the expression of mstn at 8 weeks, while col1a-2 and myog expressions also obviously improved at 12 weeks. In summary, dietary 60% FB improved tilapia muscle crispiness by altering texture and microstructure via gene-expression regulation. The minimum duration was 8 weeks to achieve crispiness in tilapia by the 60% FB diet without adverse effects on growth, immunity, and hepatopancreas function. Furthermore, the crispy texture of tilapia fillets was maintained for at least 2 months following withdrawal of the 60% FB diet after 16 weeks of continuous feeding.

Columnaris disease, caused by Flavobacterium columnare, has a broad host range and can afflict multiple families and genera of freshwater fish. In addition, our prior research found that Enoxolone emerged as the most promising candidate with a low minimum inhibitory concentration and good cost-effectiveness. However, the therapeutic effect of Enoxolone on Micropterus salmoides infected with F. columnare remains unclear, and its antibacterial efficiency in vivo has yet to be investigated. In this study, we found that the cumulative mortality rate of M. salmoides reached 70 % within 96 h post-infection with 1 × 108 CFU/mL F. columnare, and the gills exhibited clinical signs such as paleness and ischemia, accompanied by characteristic "Clavate Gill" pathological changes. Meanwhile, both the severity of these lesions and the bacterial load showed a significantly upward trend over time. In addition, following Enoxolone treatment, the mortality rate of M. salmoides infected by F. columnare was reduced by 40 %, with alleviated general pathological changes and a significantly lower number of apoptotic positive cells compared to the infected but untreated group. The relative expression of apoptosis and inflammation-related genes showed that the expression levels of Caspase-9, IL-18, TNF-α and NF-κB were significantly upregulated after F. columnare infection. However, the relative expression of Bcl-2 and IL-10 was significantly upregulated after treatment with Enoxolone. In conclusion, there was a positive correlation between the F. columnare load and gill damage in M. salmoides. In addition, Enoxolone has potential therapeutic and protective effects against gill tissue damage caused by F. columnare. Presumably, this efficacy may stem from the drug's ability to inhibit bacteria, thereby reducing gill cell apoptosis and inflammation. These findings provide new perspectives for future research and establish a groundwork for devising preventive and curative strategies against F. columnare infections.

The intestine serves as the primary defense mechanism safeguarding fish body against pathogen infiltration. Unlike cyprinid and salmonid fish, sturgeon features a distinctive special spiral valve structure within their intestines. Several studies propose that dietary lipid intake may impact the intestinal barrier function of fish. The presence of this influence within the special spiral valve intestine of sturgeon currently remains unresolved. This study aimed to explore the effects of a low or high-lipid diet on morphology, tight junction, antioxidant and immune performance, and intestinal microbiota in the spiral valve intestine of Siberian sturgeon (Acipenser baerii) (14.19 ± 0.07 g). Three diets with different lipid levels of 8.87 % (low lipid, LL), 16.93 % (moderate lipid, ML), and 24.88 % (high lipid, HL) were designed for a 70-day feeding experiment. Histological analysis revealed that the LL diet induced chronic proliferative inflammation and intestinal mucosa adhesion. In addition, the LL diet reduced the height of mucosal fold and microvilli while the HL diet shortened the microvilli only. The expression of claudin1 was inhibited by the LL diet while Claudin2 was stimulated by the HL diet. Both LL and HL diets suppressed the expression of occludin. Superoxide dismutase (SOD), catalase (CAT), and total antioxidant capacity (T-AOC) of spiral valve intestine were not sensitive to different lipid levels, but glutathione peroxidase (GSH-Px) was decreased in fish fed with the LL, and malonaldehyde (MDA) was increased in fish fed with the HL. The sturgeons fed with LL diet had declined immunoglobulin M (IgM), IgG, tumor necrosis factor α (TNFα), interleukin 1β (IL1β), IL10, and transforming growth factor β1 (TGFβ1), while HL diet had no significant effects on them. With the increase of lipid levels, the alpha diversity of spiral valve intestinal microbiota showed a downward trend. The dominant genera were mainly clostridium_sensu_stricto_1, Bacillus, Mycoplasma, and the HL group also included Lactococcus. Fourteen differentially abundant taxa were identified by LEfSe analysis, which could be biomarkers. In conclusion, a low-lipid (8.87 %) diet damaged the mechanical barrier and reduced antioxidant and immune performance. High-lipid (24.88 %) diet decreased the height of microvilli and negatively affected tight junction proteins and intestinal microbiota.

The proper lipid content in the diets is crucial for fish growth and health. However, the appropriate lipid requirement of Amur sturgeon has not been systematically studied. This study was aimed to explore the effects of dietary lipid levels on growth performance, lipid metabolism, antioxidant and immune status of juvenile Amur sturgeon (Acipenser schrenckii). Six isonitrogenous diets containing 5.11% (L5), 8.87% (L9), 12.96% (L13), 16.93% (L17), 20.84% (L21) and 24.88% (L25) lipid were fed to Amur sturgeon (4.16 ± 0.07 g) for 10 weeks. The fish in L21 group had the highest growth, feed utilization and survival rate. Based on the broken-line regression analysis of WGR, the lipid requirement for juvenile Amur sturgeon was 20.31%. HSI, hepatic crude lipid content and serum TG, TC and LDL-C contents elevated significantly with the increase of dietary lipid. Higher hepatic SOD, Anti-O2.- were found in L21 group, while MDA in both serum and liver maintained an upward trend with dietary lipid increase. The expression levels of fasn and lpl were suppressed when dietary lipid levels reached or exceeded 16.93%. While cpt1α and pparα were up-regulated, and peaked in L21 group, but down-regulated in L25 group. The expression level of il1β was on the rise as dietary lipid increased, but il10 and tgfβ1 showed a downward trend in high lipid groups. In conclusion, based on WGR, a lipid level of 20.31% in the diet was optimal for juvenile Amur sturgeon. Low (5.11%−12.96%) or high lipid (24.88%) diet decreased growth, feed utilization and survival rate. High lipid (24.88%) diet induced excessive lipid deposition, leading to intense oxidative stress, lipid metabolism disorder and inflammation.

[目的]旨在研究金藻多糖对杂交鲟幼鱼生长性能、鱼体营养成分、血清指标和肠道菌群的影响.[方法]选用270尾杂交鲟幼鱼,随机分为3组,每组设置3个重复,每个重复放30尾鱼.各组分别饲喂在基础饲料中添加0%(JZ-0,对照组)、0.3%(JZ-1)和0.6%(JZ-2)金藻多糖的饲料组.试验期为84 d.[结果]JZ-1和JZ-2组的饲料系数(FCR)显著低于JZ-0组(P<0.05);JZ-2组的肥满度(CF)和饲料效率(FE)都显著性高于JZ-0(P<0.05);成活率(SR)特定生长率(SGR),增重率(WGR),脏体比(VSI),肝体比(HSI)各组间无明显差异(P>0.05).JZ-1和JZ-2组的全鱼和肝脏粗脂肪含量显著低于JZ-0组的(P<0.05).与JZ-0组相比,JZ-1组和JZ-2组血清中谷草转氨酶(AST)和溶菌酶(LZM)活性显著升高(P<0.05);JZ-2组谷丙转氨酶(ALT)和谷胱甘肽过氧化物酶(GSH-PX)活性显著升高(P<0.05).MiseqPE300测序结果显示,添加金藻多糖的各试验组肠道菌群的Chaol、Observed species、PD whole tree和Shannon指数显著高于JZ-0组,NMDS结果显示JZ-1和JZ-2与JZ-0在肠道微生物组成上存在显著差异;试验组肠道菌群中梭杆菌门和放线菌门的比例降低,厚壁菌门和拟杆菌门的比例增加;狭义梭菌属、分节丝状菌属丰度增加.[结论]从经济效益的角度考虑,饲料中添加0.3%的金藻多糖较好.

Despite the economic and biological importance of Amur sturgeon in the world, limited full-length transcripts are available. Oxidized fish oil (OFO) might induce injury stress, but few related studies were conducted in Amur sturgeon. In this study, an 8-week experiment with diets containing 6% fresh fish oil (FFO) or 6% OFO was conducted, and Iso-Seq combined with RNA-Seq analysis were used to explore the molecular response to dietary OFO in juvenile Amur sturgeon. A total of 18,408 high quality, unique full-length isoforms were generated by Iso-Seq, with an average length of 2180 bp and an N50 of 2793 bp. similar to 382 million clean reads were obtained from RNA-Seq, and the mapping ratio of the clean reads to the unigenes was 84.25% similar to 88.25%. There were 839 differently expressed genes (DEGs) in FFO vs OFO, of which 360 were up-regulated, and 479 were downregulated. DEGs were mapped into 276 KEGG pathways, of which 45 pathways were significantly influenced. The proportion analysis of 45 significantly changed pathways revealed that human disease was the most enriched category, and cancers, endocrine system, signal transduction, cell growth and death and carbohydrate metabolism was the most affected subcategory in each category, indicating that OFO might induce cancers, endocrine disorder, and carbohydrate metabolism disruption. Further analysis discovered that transcriptional misregulation in cancer and FOXO signaling pathway were the top2 regulated pathways. PPI network analysis showed that foxo1 and pik3c alpha were identified as hub genes in response to dietary OFO in Amur sturgeon. The present study provided the first systematic full-length transcriptome dataset of Amur sturgeon and laid a solid foundation for further research on the molecular mechanism in response to dietary OFO.

A ten-week feeding trial was performed to evaluate the effects of chlorogenic acid (CGA) on the growth, body color, antioxidant activity, serum biochemical parameters, and immune response of koi. Five diets were formulated to contain 0 (control), 200 (CGA-2), 400 (CGA-4), 600 (CGA-6), and 800 (CGA-8) mg/kg CGA for the rearing of experimental fish. By means of an analysis by polynomial orthogonal contrasts, it was determined that dietary supplementation with CGA had no significant effects on the growth performance of koi ( P > 0.05), while body color indices (redness, yellowness, and lightness) showed a linear order polynomial ( P < 0.05). A quadratic response was found for the relationship between total carotenoid in scale of koi and dietary CGA levels, with an optimum level of 381.84 mg/kg. Dietary CGA levels and lysozyme activity showed a cubic relationship polynomial model, with an optimum level of 383.89-975.73 mg/kg. TGF- β expression in the head-kidney of koi was obviously improved by 600 mg/kg CGA diet ( P < 0.05). And in regards to effect in serum, SOD and CAT activities was best explicated by a linear order polynomial, while the quadratic and cubic relationship polynomial models represented the GSH and GSH-Px activities, which the optimal supplementation level of CGA was estimated at 550.78 and 231.74-782.66 mg/kg, respectively. The relationship between ALT activity and CGA supplementation was best explicated by quadratic relationship polynomial, with an optimum level of 522.78 mg/kg. Based on the model observed, 522.78-600 mg/kg CGA was the recommended supplementation in diet that improved the body color, antioxidant activity, biochemical parameters, and immune response of koi.

This study was carried out to explore the effects of dietary oxidized fish oil on growth, feed utilization, health status and fillet quality of juvenile Amur sturgeon (A. schrenckii) (initial mean body weight = 70.0 ± 0.02 g). An 8-week experiment with diets containing 6% fresh fish oil (FFO) or 6% oxidized fish oil (OFO) was conducted. The peroxide values (POV) of fresh and oxidized fish oil were 9.14 and 384.73 meq/kg, respectively. The results indicated that compared to the FFO group, dietary OFO had no significant influence on growth (P > 0.05), but increased feeding rate (FR) and decreased productive protein value (PPV) significantly (P < 0.05). The fish in the OFO group had lower serum high-density lipoprotein cholesterol (HDL-C), albumin (ALB), and the ratio of ALB to globulin (GLOB), and higher serum malonaldehyde (MDA) and superoxide anion free radical (O2−) than those in the FFO group (P < 0.05). OFO induced inflammatory cell infiltration in the liver, and the expressions of hepatic inflammatory cytokines were significantly up regulated in the fish fed with OFO (P < 0.05). The fish in the OFO group showed abnormal yellow skin, and the yellowness value of the dorsal muscle was significantly elevated in comparison with the FFO group (P < 0.05). The contents of muscle protein, lipid, and glycogen were significantly declined by dietary OFO (P < 0.05). Dietary OFO affected the muscle essential amino acid (EAA) composition remarkably, among which the proportions of Ile and Met were reduced while Leu was promoted significantly (P < 0.05). The fish fed with OFO had significantly higher n-6 polyunsaturated fatty acids (PUFA) proportion and n-6 PUFA/n-3 PUFA ratio (P < 0.05) than the fish fed with FFO, but there were no changes in the proportion of saturated (SFA), monounsaturated fatty acid (MUFA) and n-3 PUFA (P > 0.05). The total free amino acid (FAA) was enhanced significantly by dietary OFO, but the delicious amino acid (DAA) proportion was decreased in the muscle of the fish fed with OFO (P < 0.05). In summary, dietary OFO had no significant influence on growth, but decreased feed utilization of Amur sturgeon. Dietary OFO impaired the health status of Amur sturgeon by inducing oxidative stress, lowering serum HDL-C, ALB and causing liver damage. Dietary OFO adversely affected the fillet quality of Amur sturgeon by altering body color, muscle proximate composition, glycogen content, EAA, fatty acid and FAA profiles.

An 8-week growth trial was performed to evaluate the effects of grape seed proanthocyanidins (GSPs) on growth, digestive enzymes, body composition, intestinal microbiota, serum immunological, anti-oxidative and biochemical parameters of juvenile hybrid sturgeon (Acipenser baeri Brandt female x A. schrenckii Brandt male). Fish were randomly divided to control, GSPs-50 and GSPs-100 groups, which were fed with a basal diet and basal diet supplemented with 50 and 100 mg/kg GSPs, respectively. Growth performance and digestive enzymes were improved by GSPs in sturgeon (p < .05). Lysozyme was clearly increased in serum when sturgeon fed with GSPs diets, while the thiobarbituric acid reactive substances (TBARS) displayed opposite trend (p < .05). Myeloperoxidase and glutathione peroxidase in serum of GSPs-50 were higher than control and GSPs-100 (p < .05). Serum parameters showed alanine aminotransferase, alkaline phosphatase and gamma-glutamyl transpeptidase of GSPs-50 were lower than control (p < .05). Compared with the control treatment, GSPs-100 reduced alanine aminotransferase and gamma-glutamyl transpeptidase and increased aspartate aminotransferase and lactate dehydrogenase (p < .05). High-throughput sequencing revealed that adding 50 mg/kg GSPs not only modified the microbiota diversity, but also reduced the relative abundance of Aeromonas in sturgeon intestine. In conclusion, GSPs are a promising feed additive to promote growth, immunity, antioxidant and digestive enzyme activities and improve serum biochemical parameters and intestinal microbiota of hybrid sturgeon.

The present study was to investigate the effect of dietary Tribonema ultriculosum supplementation on growth performance, fillet nutritional quality and immunity of rainbow trout Oncorhynchus mykiss (165.26 +/- 0.57 g, mean +/- SD). Three diets containing 0 (control), 50 g/kg and 100 g/kg T. ultriculosum (TU) were introduced to triplicate groups of the experimental fish for 90 days. Then, a lipopolysaccharide (LPS) stress experiment was conducted to evaluate the effect of microalgal addition on fish immune response. Compared to the control, microalgal addition significantly increased fish feed intake and growth. Dietary T. ultriculosum supplementation significantly increased the contents of palmitoleic acid, eicosapentaenoic acid (EPA) and docosahexaenoic acid in fillet. The addition of T. ultriculosum significantly increased the activity levels of spleen glutathione peroxidase (before LPS stress) and superoxide dismutase (after LPS stress), and simultaneously decreased the spleen malondialdehyde content compared to the control. In terms of the immune response, fish fed diets containing T. ultriculosum had a higher level of lysozyme activity (before LPS stress), immunoglobulin M content (before and after LPS stress) and hepcidin expression (after LPS stress) compared to the control. These results suggest that T. ultriculosum can be used to increase fish growth, fillet nutritional quality and immunity.

肠道作为一个大型的生态系统,存在数量巨大的微生物,肠道健康会直接影响到动物对饲料中营养物质的消化吸收以及机体自身的生长性能.肠道菌群是动物机体不可缺少的组成部分,在维持肠道健康、抵抗病原菌的入侵、调节物质代谢、能量吸收、器官发育以及机体免疫等方面发挥着重要作用.肠道菌群的种类和数量在动物健康时是处于稳定平衡状态的.

The aim of the study is to investigate whether dietary Chlorella sorokiniana supplementation could improve growth performance, antioxidant status, and immune response of Oncorhynchus mykiss. Three isonitrogenous (47%) and isolipidic (16.5%) diets supplemented with 0% (Control), 5% (5% CS), and 10% C. sorokiniana meal (10% CS) were assigned to O. mykiss (three replicates per diet, 30 fish in each replicate, initial body weight 165.24 ± 0.46 g). The results indicated that O. mykiss fed with 5% CS diet had an increased feeding rate (FR), specific growth rate (SGR), and weight gain rate (WGR) compared to the control (P < 0.05). Dietary 5% or 10% C. sorokiniana supplementation significantly increased activity levels of superoxide dismutase (SOD) in the liver and catalase (CAT) in the liver and head kidney. In addition, dietary supplementation with 10% C. sorokiniana also significantly increased activity level of glutathione peroxidase (GPX) and simultaneously decreased contents of malondialdehyde (MDA) in the liver and head kidney. Furthermore, fish fed with 5% CS or 10 CS diet demonstrated increased activity level of lysozyme (LYZ), higher content of immunoglobulin M (IgM), and upregulated transcriptional expression of tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β), hepcidin (HEP), and nuclear factor kappa-B (NF-κB) in the head kidney. Based on fish growth performance, antioxidant capacity, and immune response, dietary supplementation of 5% C. sorokiniana was recommended.

Infectious hematopoietic necrosis virus (IHNV) is a major fish viral pathogen causing acute clinical disease and death in a variety of salmonids. IHNV isolates have been classified into five major genogroups according to the phylogenetic analysis of partial G gene fragments or the complete G gene sequence: U, M, E, L and J. Genogroup U strains have been reported in North America and Japan prior to 1982, and genogroup J is the only genogroup that has been reported in China. Here, one of IHNV strain (BjLL) was isolated from a local farm in China and were characterized in this study. The homogenate tissues of infected fry induced IHNV-positive cytopathic effects in epithelioma papulosum cyprinid (EPC) cells that were confirmed by RT-PCR and sequencing. The complete genome sequence of BjLL comprised 11,129 nucleotides, which had been submitted to GenBank (accession no. MF509592). By the sequence comparison and phylogenetic analysis for the G gene sequence of BjLL with 51 reference sequences in GenBank, we confirmed that this Chinese isolate belonged to genogroup U. Furthermore, virus exposure experiments with juvenile rainbow trout were conducted to assess the virulence and pathogenicity of BjLL. Compared with GS-2014 of genogroup J, BjLL was an obviously less virulent strain that could result in lower mortality. Besides, typical clinical symptoms and pathological damages could be seen in fish following infection of BjLL. The present study is the first report of genogroup U IHNV infection in China and will provide essential information for future studies on pathogenesis of IHNV BjLL and development of efficient control strategies.

研究旨在探究饲料中不同脂肪水平对西伯利亚杂交鲟(Acipenser baerii Brandt♀×A.schrenckii Brandt ♂)幼鱼生长、饲料消化率、血清生化指标及肌肉脂肪酸组成的影响.以鱼油为脂肪源,配制4种脂肪水平分别为5％(D05)、10％(D10)、15％(D15)和20％(D20)的等氮饲料.选用初始体重为(152.83±0.67)g的杂交鲟,随机分为4组,每组3个重复,每个重复25尾鱼.养殖周期为12周.结果 显示,饲料中不同脂肪水平对杂交鲟的生长性能有显著影响(P＜0.05).其中,D15组杂交鲟幼鱼的末均重(FBW)、增重率(WGR)和特定生长率(SGR)显著高于D05、D10和D20组(P＜0.05),饲料效率(FE)显著高于D05和D10组(P＜0.05).随着饲料中脂肪含量的增加,杂交鲟幼鱼脏体比(VSI)、肝体比(HSI)及肌肉、肝脏中的脂肪含量显著上升(P＜0.05).饲料中不同脂肪水平对干物质(ADCd)、蛋白质(ADCp)表观消化率无显著影响(P＞0.05).D10、D15和D20组脂肪表观消化率(ADCf)显著高于D05组(P＜0.05).D15组能量表观消化率在各组中最高,显著高于D05和D10组(P＜0.05).随着饲料中脂肪水平的增加,血清超氧化物歧化酶(SOD)、总抗氧化能力(T-AOC)和髓过氧化物酶(MPO)的活性均显著升高,谷胱甘肽过氧化物酶(GSH-Px)活性显著下降(P＜0.05).此外,肝功能指标谷丙转氨酶(ALT)、谷草转氨酶(AST)、碱性磷酸酶(ALP)和乳酸脱氢酶(LDH)的活性也随饲料中脂肪水平的升高呈递增趋势(P＜0.05).肌肉中的各脂肪酸含量与饲料中脂肪酸含量呈显著的线性正相关(R2＞0.90,P＜0.05).综合各指标因素判断,西伯利亚杂交鲟幼鱼饲料中适宜的脂肪水平为15％,P/E为23.54 mg/kJ.

A 10-week experiment was conducted to evaluate the effects of dietary lipid levels on growth, feed utilization, lipid deposition, health status and digestive enzyme activities of juvenile Siberian sturgeon (Acipenser baerii). Six isonitrogenous diets were formulated with lipid levels at 51.1 (L5), 88.7 (L9), 129.6 (L13), 169.3 (L17), 208.4 (L21) and 248.8 g/kg (L25). The sturgeons fed with L17 had the highest growth and feed utilization. Higher dietary lipid obtained significantly lower PPV than that of L17 (p < .05). Based on WGR, PPV, the optimal dietary lipid was estimated at 169.9, 176.0 g/kg. The lipid deposition in the whole body, muscle and liver enhanced significantly as the dietary lipid increased (p < .05). Dietary lipid levels affected serum biochemical parameters, with the highest AST, TC, LDL-C and LDL-C/TC in L21 or L25 group and highest HDL-C in the L17 group. Serum antioxidants, oxidants and liver MDA content maintained upward trends with increasing dietary lipid from 51.1 to 248.8 g/kg (p < .05). Lipase activity in the spiral valve intestine increased when dietary lipid rose from 51.1 to 169.3 g/kg, but declined when lipid level up to 208.4 and 248.8 g/kg (p > .05). To sum up, the optimal dietary lipid was 169.9–176.0 g/kg for juvenile Acipenser baerii.