Heat stress induced hepatocyte apoptosis in largemouth bass Micropterus salmoides via IRE1α/TRAF2/ASK1/JNK pathway

Heat stress(HS)has been shown to adversely affect fish livers and can lead to extensive apoptosis.To investigate the relationship between endoplasmic reticulum(ER)stress and HS-induced apoptosis in fish livers,we isolated and cultured primary hepatocytes of largemouth bass,Micropterus salmoides by trypsin method,then established an in-vitro model of liver cells under HS(35℃).The contents of lactic dehydrogenase(LDH)and hydrogen peroxide(H2O2)were determined to evaluate the effects of HS on hepatocyte injury and oxidative stress.RT-qPCR was performed to discover the key genes in unfolded protein response(UPR)pathways involved at different HS duration.ERS inhibitor 4-PBA and IRE1αinhibitor 4μ8C were used to further investigate the effects of HS on IRE1αapoptosis pathway in hepatocytes.Results show that HS led to significant increases in the release of LDH,the content of H2O2,and the expressions of oxidative protein folding genes(ero1αand pdi)under HS,suggesting severe hepatocyte injury and oxidative stress happened in heat-stressed largemouth bass hepatocytes.The continuous activation of IRE1αpathway genes(grp78,grp94,atf6,perk,eif2a,atf4,chop,ire1α,traf2,ask1,jnk1,and jnk2)indicated that HS led significantly to ER stress.In particular,the mRNA expression levels of ER stress-related genes(grp78,grp94,atf6,perk,ire1α,chop,jnk1,and jnk2)in the high temperature(HT)+4-PBA group and the HT+4μ8C group were significantly down-regulated under HS.After 4μ8C treatment,the expression levels of apoptosis-related genes(caspase-2,caspase-3,caspase-6,caspase-7,caspase-8,caspase-9,and caspase-10)and LDH content were significantly decreased,whereas the cell survival rate was significantly increased when given 4-PBA or 4μ8C treatment.These findings demonstrate that HS could induce liver apoptosis of largemouth bass through the IRE1αpathway,which may act as a key switch mediating liver apoptosis of largemouth bass under HS.

Protective efficacy evaluation of immunogenic protein AHA_3793 of Aeromonas hydrophila as vaccine candidate for largemouth bass Micropterus salmoides

Aeromonas hydrophila is a Gram-negative pathogen that can infect various fish,including largemouth bass(Micropterus salmoides),which have caused huge economic losses.In present study,largemouth bass anti-A.hydrophila antibodies were produced,then a highly immunogenic outer membrane proteins,AHA_3793,was identified by combined western blotting and mass spectrometry analysis.Moreover,AHA_3793 was expressed,and its immunogenicity was further verified by western blotting.Subsequently,the protective efficacy of AHA_3793 were evaluated in largemouth bass.The results showed that rAHA_3793 could produce a relative percentage survival(RPS)of 61.76% for largemouth bass against A.hydrophila challenge.ELISA analysis showed the specific serum antibodies of largemouth bass against rAHA_3793 and A.hydrophila in vaccinated group in weeks 4 and 5 after immunization were significantly higher than those in control group,which suggested that rAHA_3793 induced production of specific serum antibodies against rAHA_3793 and A.hydrophila.The qRT-PCR analysis showed that expressions of CD4-2 and MHC Ⅱα were also significantly up-regulated after immunization.These results collectively demonstrated that rAHA_3793 could induce a strong humoral immune response of largemouth bass,and then produce high immune protection ef fects against A.hydrophila infection.

Effects of Different Feeding Patterns on the Growth of Micropterus salmoides

Three experimental groups with different feeding frequencies,different feeding rates and compensatory feeding were set up to study their effects on the growth of Micropterus salmoides.The results showed that different feeding rates of 2%,3%and 4%had no significant effects on the growth of M.salmoides.Therefore,before the individual weight of 50 g,the fish could be fed with a feeding rate of 4%,which could be gradually decreased to 2%in the later period.Under the condition of relatively fixed feeding rate,different feeding frequencies had an impact on the growth of M.salmoides.Under the conditions of suitable water temperature,it is reasonable to feed twice daily.The experimental fish fed for 5 d and then deprived of feed for 1 d showed fully compensatory growth,and there were no significant differences in weight gain rate,daily weight gain and specific growth rate compared with the continuous feeding group(P>0.05).Therefore,according to the feeding conditions of fish in the breeding process,stopping feeding for 1 d every 5 d could save feed and labor and improve breeding efficiency.

大口黑鲈(Micropterus salmoides)不同养殖模式氮磷收支及养殖效果研究

为了揭示池塘内循环流水养殖模式(Inner-Pond Raceway Aquaculture,IPRA)氮磷收支变化及养殖效果情况,阐明其生态特征及营养物质的来源与归宿,合理评价IPRA的经济与生态效益,通过定期采样计算氮磷的输入和输出项目,同时设置传统常规养殖池塘(usual pond aquaculture,UPA)为对照组。结果表明:(1)两种养殖模式中,饲料是池塘氮、磷输入的主要来源,分别占IPRA和UPA池塘氮输入的95.02%±2.31%和94.57%±1.82%,占两种模式磷输入的93.19%±2.75%和91.81%±4.44%;(2)底泥沉积是氮、磷输出的主要方式,占IPRA和UPA氮输出的45.16%±1.31%和53.98%±1.48%,占磷输出的40.28%±3.19%和59.59%±4.45%,差异显著(P<0.05),其次是养殖产出,IPRA渔获物氮输出比例37.73%±0.91%高于UPA的35.07%±0.99%,差异不显著(P>0.05),磷输出比例25.50%±1.77%显著高于UPA的20.78%±1.33%(P<0.05);(3)IPRA对氮的绝对和相对利用率高于UPA,但差异不显著(P>0.05),而对磷的利用率显著高于UPA(P<0.05),IPRA提高了养殖对象对氮、磷的吸收利用率;(4)IPRA耗水系数、排水系数及排污系数均显著低于UPA(P<0.05),但IPRA养殖效益显著高于UPA(P<0.05)。综上所述,IPRA是一种清洁高效的新型养殖模式,可以进行推广应用。本研究旨在为今后更好地开展IPRA水质管理和科学养殖提供数据支撑,同时为IPRA模式在节水生态、经济效益等评价方面提供理论依据。

RAPD Analysis of Micropterus salmoides and Tilapia nilotica

The intra-population phylogenetic relationship between Micropterus salmoides and Tilapia nilotica was analyzed by random amplified polymorphic DNA （ RAPD） technique. The results showed that the similar coefficient of bands between M. salmoides and T. nilotica was 0.236, and the genetic distance was 0. 764, which indicated that M. salmoides had a distant relationship with T. nilotica.

抗大口黑鲈(Micropterus salmoides)蛙虹彩病毒药效模型的构建及其抗病毒中药筛选

大口黑鲈蛙虹彩病毒(LMBV)是一种严重危害大口黑鲈养殖的病害,但目前缺乏有效的防控手段。通过研究水温、鱼体大小以及攻毒剂量等条件对大口黑鲈感染蛙虹彩病毒的影响,构建体内抗病毒药效筛选模型,同时利用MTT法构建体外药物筛选模型,进而通过体外和体内药效模型,对29种中草药进行抗病毒药效评价,对筛选出药效最佳的2种中药进行体外和体内抗病毒药效评价。结果表明:水温和鱼体大小是影响体内药效模型的2个关键因子,最佳体内药效模型条件为:水温为25℃,鱼体大小20 g,攻毒剂量为0.1 mL 10^(9.33) TCID_(50)/mL。结合体内和体外药效模型结果,筛选出紫花地丁和黄连这2种中药具有较好的抗病毒效果的中草药。体内药效结果表明:黄连和地丁的添加量为0.6 g/kg和1.2 g/kg时,其对大口黑鲈的保护率最高均达到40%,而两者用药后病毒在肝组织的抑制率分别可达71.5%和67.0%。组织病理学结果表明,当药物使用浓度为0.6 g/kg和1.2 g/kg时,可有效降低因大口黑鲈蛙虹彩病毒感染所导致的肝和肾等组织的病理学损伤。上述结果表明,黄连和地丁均具有较好的抗蛙虹彩病毒的作用。

Denitrification potential evaluation of a newly indigenous aerobic denitrifier isolated from largemouth bass Micropterus salmoides culture pond

This work evaluates the application potential of a new indigenous aerobic denitrifi er, strain Pseudomonas CW-2, isolated from a largemouth bass culture pond. The rate of ammonium-N removal by strain CW-2 was approximately 97% at a DO concentration of 5.2 mg/L. Furthermore, when nitrate and ammonia coexisted, the strain gave priority to assimilating ammonia, and thereafter to denitrifi cation. Under optimal cultivation conditions, citrate and acetate were the carbon resources, C/N was 8, dissolved oxygen was 5.2 mg/L, and pH was 7; the removal rate of ammonium reached nearly 90%. The changing patterns of different bacteria in strain CW-2-treated and the control pond water were also compared. Lower levels of ammonia, nitrite, and phosphates were observed in the treated water as compared with the controls. Meanwhile, phylum-level distributions of the bacterial OTUs revealed that P roteobacteria, Bacteroidetes, Planctomycetes, and N itrospirae continuously changed their relative abundances in relation to carbon and the addition of strain CW-2; this finding implies that the conventional denitrifi cation process was weakened under the ef fects of carbon or the presence of strain CW-2. We propose that strain CW-2 is a promising organism for the removal of ammonium in intensive fish culture systems, according to our evaluations of its denitrifi cation performance.

Dietary black soldier fly oil enhances growth performance,flesh quality,and health status of largemouth bass(Micropterus salmoides)

The study aimed to assess the effects of dietary black soldier fly oil(BSFO)on the growth performance,flesh quality,and health status of largemouth bass(Micropterus salmoides).Six iso-nitrogenous and isolipid diets were formulated by substituting fish oil and soybean oil(1/2,wt/wt)with BSFO in percentages of 0%,20%,40%,60%,80%,and 100%,respectively.The diets were fed to 960 fish(initial body weight=16.5 g)in four replicates for 8 weeks.Indicators related to growth performance,body composition,hematology,flesh quality,expression of genes related to inflammatory cytokines and apoptosis,and the response of fish to Aeromonas veronii challenge were analyzed.The results showed that the weight gain rate was numerically improved in all BSFO substitution groups,ranging from 9.3%to 44.0%compared to the control group.The highest survival rate and the lowest hepatosomatic index and condition factor were observed in the BFSO20 group.In terms of flesh quality,the water-holding capacity of the dorsal muscle was elevated with higher levels of dietary BSFO.However,significant changes in texture properties(cohesiveness,gluing,and chewiness)were observed in the BSFO20 group(P<0.05).Six hematological parameters related to glycolipid and liver function were optimized in most of the BFSO substitution groups.Furthermore,the expressions of six inflammation-and apoptosis-related genes(IL-1β,Bcl-xl,BAX,caspase8,TNF-α,and IL-10)were significantly affected by dietary BSFO(P<0.05).Following bacterial challenge,the seven-day cumulative survival rates of fish were considerably increased from 10.0%in the control group to 60.0%and 66.7%in the BSFO80 and BSFO100 groups,respectively.One-variable linear regression analysis revealed that various parameters related to fish growth,flesh quality,and health status were significantly influenced by dietary BSFO substitution levels in a dose-dependent manner(P<0.05).In conclusion,substituting around 20%of dietary fish oil and soybean oil with BSFO is promising in improving the growth performance and flesh quality of M.salmoides.However,to enhance immunity and disease resistance,it is recommended to further increase the inclusion of BSFO in the diet.

Effects of paraprobiotics on bile acid metabolism and liver health in largemouth bass(Micropterus salmoides)fed a cottonseed protein concentrate-based diet

Cottonseed protein concentrate is a sustainable fishmeal alternative in aquafeed.A 10-week experiment was conducted to investigate the effects of a cottonseed protein concentrate-based diet with and without multi-strain yeast fractions(MsYF)on growth,bile acid metabolism,and health in largemouth bass.Four hundred fish(54.0±0.0 g)were casually distributed into 16 tanks(4 replicates/diet).Fish were fed with 4 iso-nitrogen and iso-energetic diets 3 times daily,including a fishmeal diet(FM),a soy protein concentrate-based diet(SPC;replacing 81%fishmeal protein),a cottonseed protein concentrate-based diet(CPC;replacing 81%fishmeal protein),and a CPC diet supplemented with 800 mg/kg MsYF(CPCY).Results showed that the survival of SPC was the lowest,i.e.,48%,with no apparent diet effect among other treatments;we omitted the SPC in additional analyses.Fish fed cottonseed protein concentrate-based diets showed lower growth than FM(P<0.05).Fish fed CPC showed the highest nuclear dense hepatic phenotypes ratio(50%),followed by CPCY(33%)and FM(17%).Further,dietary CPC increased hepatic total cholesterol and triglyceride levels with concurrently increased cholesterol syn-thesis but decreased triglyceride synthesis-associated transcription levels(P<0.05).Furthermore,di-etary CPC increased bile acid synthesis but decreased bile acid transport-associated transcription levels(P<0.05),and then induced an increment of plasma cholic acid and hepatic chenodeoxycholic acid content and the decrement of genus Romboustia(P<0.05).Regarding the effect of MsYF,fish fed CPCY reduced hepatic lipid accumulation and total plasma bile acid content(P<0.05)compared to CPC,suggesting an improvement in liver health.Also,dietary MsYF could reverse the microbiota community structure showing a similar gut microbial composition to FM.In conclusion,81%of fishmeal protein replaced by cottonseed protein concentrate suppressed growth and liver health,while dietary MsYF might mitigate the negative impact of a high cottonseed protein concentrate level diet on liver functions via gut microbiota regulation.

Dietary lysophospholipids improves growth performance and hepatic lipid metabolism of largemouth bass(Micropterus salmoides)

This study was conducted to evaluate the influence of dietary lysophospholipids combined with 1%dietary fish oil reduction on the growth performance and hepatic lipid metabolism of largemouth bass(Micropterus salmoides).Five isonitrogenous feeds were prepared with lysophospholipids at 0%(fish oil group,FO),0.05%(L-0.05),0.1%(L-0.1),0.15%(L-0.15)and 0.2%(L-0.2),respectively.The dietary lipid was 11%in the FO diet and 10%in the other diets.Largemouth bass were fed for 68 d(initial body weight=6.04±0.01 g)with 4 replicates per group and 30 fish per replicate.The results showed that the fish fed diet containing 0.1%lysophospholipids had higher digestive enzyme activity and obtained better growth performance compared to the fish fed FO diet(P<0.05).The feed conversion rate in the L-0.1 group was significantly lower than that in the other groups.Serum total protein and triglyceride contents in L-0.1 group were significantly higher than those in other groups(P<0.05)and the contents of total cholesterol and low-density lipoprotein cholesterol in L-0.1 group were significantly lower than those in FO group(P<0.05).The activity and genes expression of hepatic glucolipid metabolizing enzymes in L-0.15 group were significantly increased compared to those in FO group(P<0.05).Reducing 1%fish oil along with 0.1%lysophospholipids added to the feed could improve the digestion and absorption of nutrients,enhance the activity of liver glycolipid metabolizing enzymes,and thus effectively promote the growth of largemouth bass.

Isolation and characterization of a novel strain(YH01) of Micropterus salmoides rhabdovirus and expression of its glycoprotein by the baculovirus expression system

As one of the most important aquatic fish,Micropterus salmoides suffers lethal and epidemic disease caused by rhabdovirus at the juvenile stage.In this study,a new strain of M.salmoides rhabdovirus(MSRV)was isolated from Yuhang,Zhejiang Province,China,and named MSRV-YH01.The virus infected the grass carp ovary(GCO)cell line and displayed virion particles with atypical bullet shape,300–500 nm in length and 100–200 nm in diameter under transmission electron microscopy.The complete genome sequence of this isolate was determined to include 11 526 nucleotides and to encode five classical structural proteins.The construction of the phylogenetic tree indicated that this new isolate is clustered into the Vesiculovirus genus and most closely related to the Siniperca chuatsi rhabdovirus.To explore the potential for a vaccine against MSRV,a glycoprotein(1–458 amino acid residues)of MSRV-YH01 was successfully amplified and cloned into the plasmid pFastBac1.The high-purity recombinant bacmid-glycoprotein was obtained from DH10Bac through screening and identification.Based on polymerase chain reaction(PCR),western blot,and immunofluorescence assay,recombinant virus,including the MSRV-YH01 glycoprotein gene,was produced by transfection of SF9 cells using the pFastBac1-gE2,and then repeatedly amplified to express the glycoprotein protein.We anticipate that this recombinant bacmid system could be used to challenge the silkworm and develop a corresponding oral vaccine for fish.

A new single-cell protein from Clostridium autoethanogenum as a functional protein for largemouth bass(Micropterus salmoides)

Clostridium autoethanogenum protein(CAP)is a new single-cell protein source originating from inactivated bacteria.An in vitro digestion experiment and an 8-wk growth experiment were conducted to evaluate the molecular weight distribution of the CAP hydrolysate,and the effects of dietary CAP levels on the growth performance,plasma parameters,hepatic and intestinal health,and the diversity of gutadherent microbiota of largemouth bass(Micropterus salmoides).The fish(initial body weight of 47.99±0.01 g)were fed diets where CAP gradually replaced 0%(CAP0),12.5%(CAP12.5),25%(CAP25),37.5%(CAP37.5)and 50%(CAP50)of low-temperature steam dried anchovy fish meal(LTFM)in the diet.Results showed that the content of peptides below 1,000 Da in the CAP hydrolysate(0.56 mg/mL)was higher than that of the LTFM hydrolysate(0.48 mg/mL).Dietary CAP inclusion had no negative effect on growth performance,while whole-body lipid content significantly reduced in the CAP25 and CAP50 groups(P<0.05).The plasma alanine aminotransferase activities and triglyceride concentrations in the CAP inclusion groups were significantly lower than those in the CAP0 group(P<0.05).The plasma aspartate aminotransferase activity was significantly reduced in the CAP37.5 group(P<0.05).The richness and diversity of the gut-adhesive microbiota and the proportion of Clostridium sensu stricto 12 in the CAP50 group were significantly higher than those in the CAP0 group(P<0.05).Dietary CAP inclusion inhibited inflammatory responses by down-regulating the mRNA levels of interleukin 1b(IL1b),IL10 and transforming growth factor b1(P<0.05)in the liver.The mRNA levels of acetyl-CoA carboxylase 1 were significantly down-regulated in the CAP12.5,CAP25 and CAP37.5 groups(P<0.05),while that of fatty acid synthase was significantly down-regulated in the CAP50 group(P<0.05).These results demonstrate that dietary CAP inclusion could improve the hepatic and intestinal health of largemouth bass,and can be helpful to further develop CAP as a functional feed ingredient.

Effects of fish meal replacement with Chlorella meal on growth performance,pigmentation,and liver health of largemouth bass(Micropterus salmoides)

Chlorella meal is a potential protein source for aquafeeds.However,the physiological response of carnivorous fish fed Chlorella meal remains elusive.This study evaluated the effects of replacing dietary fish meal with Chlorella meal on growth performance,pigmentation,and liver health in largemouth bass.Five diets were formulated to replace dietary fish meal of 0%(C0,control),25%(C25),50%(C50),75%(C75),and 100%(C100)with Chlorella meal,respectively.Total 300 fish(17.6±0.03 g)were randomly assigned to 15 tanks(3 tanks/group).Fish were fed the experimental diet twice daily for 8 weeks.The increased dietary Chlorella meal quadratically influenced the final body weight(FBW),weight gain rate(WGR),specific growth rate(SGR),and feed intake(FI),which were significantly lower in the C100 group than in the other groups(P<0.05).The feed conversion ratio(FCR)increased linearly or quadratically with dietary Chlorella meal.Dietary Chlorella meal linearly or quadratically increased the lutein content of plasma,liver,and dorsal muscle of largemouth bass(P<0.05).Compared to the C0 group,all supplemented Chlorella meal groups significantly improved the yellowness(b*)of the dorsal body(1.5 to 2.0 fold),abdominal body(1.5 to 1.8 fold),and dorsal muscle(3.8 to 5.4 fold)of largemouth bass(P<0.05).In addition,compared to the C0 group,the liver vacuolation area of fish was significantly increased in the C75 and C100 groups(P<0.05).Transcriptional levels of apoptosis-related genes of b-cell lymphoma-2(bcl2),caspase-9-like(casp9),and caspase-3a(casp3)were markedly upregulated(0.9 to 1.6 fold)in the C100 group compared to the C0 group(P<0.05).Based on the quadratic regression analysis between FBW,WGR,or SGR and dietary Chlorella meal level,largemouth bass had the best growth when replacing 31.7%to 32.6%of fish meal with 15.03%to 15.43%dietary Chlorella meal.The present results indicated that dietary supplementation with Chlorella meal(11.85%to 47.45%)significantly enhanced the pigmentation;however,total replacement of fish meal(40%)with Chlorella meal(47.45%)caused growth retardation,apoptosis,and liver damage in largemouth bass.

玉屏风多糖复合益生菌对大口黑鲈响应迟缓爱德华氏菌脂多糖的免疫调节作用

为探究玉屏风多糖复合益生菌对大口黑鲈(Micropterus salmoides)响应迟缓爱德华氏菌(Edwardsiellatarda)脂多糖(LPS)的免疫调节作用,选取450尾健康大口黑鲈(11±2)g,随机分为对照组、复合益生菌组(CPB)、玉屏风多糖组(YPF)、未发酵玉屏风多糖复合益生菌组(UYP)和发酵玉屏风多糖复合益生菌组(FYP)5组,饲喂28 d后注射迟缓爱德华氏菌LPS,在注射后0、8、24、48 h采样,测定免疫器官生长指数、血清生化指标、组织抗氧化指标和肝脏免疫相关基因表达。结果显示:饲喂28 d后,FYP组头肾指数显著高于对照组和YPF组。在LPS免疫刺激0 h时,实验组血清总抗氧化能力均显著高于对照组。免疫刺激8 h时UYP组和FYP组血清谷草转氨酶和谷丙转氨酶活性显著高于对照组,肝脏白细胞介素-1和肿瘤坏死因子-α浓度显著高于对照组,肝脏核因子-κB抑制物激酶、白细胞介素-1β、白细胞介素-8相对表达量较对照组均显著下调。与其他实验组相比,FYP组在免疫刺激后8 h时肠组织和肝组织超氧化物歧化酶活性显著高于其他组,48 h时血清免疫球蛋白M浓度显著高于其他组。综上,本研究表明玉屏风多糖与复合益生菌均能提高大口黑鲈的免疫能力,发酵玉屏风多糖复合益生菌效果更佳。

大口黑鲈鱼舱工厂化高效节能养殖技术

为探索大口黑鲈(Micropterus salmoides)高效节能工厂化养殖技术,进行了试验示范,配套工厂化车间,采用双循环三分离尾水处理技术,进行苗种放养、苗种适时分级、饲料选择与投喂、水体环境调控、鱼病防控等,实现一年生产两批鲈鱼,年产量10.57万kg,年单产163.12 kg/m^(3),年单位效益1908.33元/m^(3),年投入产出比1∶1.50,每日电费仅有106.98元,每日从车间外池塘补水3.09%,取得了良好经济效益、社会效益和生态效益。

两种蛋氨酸对大口黑鲈(Micropterus salmoide)生长性能、肌肉品质与抗氧化能力的影响

为探究在酶解羽毛粉替代鱼粉的饲料中蛋氨酸对大口黑鲈(Micropterus salmoide)生长性能和肌肉品质的影响,配制三种饲料,对照组投喂基础饲料,晶体组添加晶体蛋氨酸,螯合组添加锌螯合蛋氨酸。挑选初始体重为(9.68±0.05)g(平均值±标准差)的大口黑鲈幼鱼180尾,随机分到9个养殖缸中,每个养殖缸20尾,并将9个养殖缸随机分成3组(每组3重复),进行8周养殖。结果表明,添加两种蛋氨酸后,大口黑鲈WGR与SGR显著提高(P<0.05)。两种蛋氨酸对大口黑鲈肌肉水分和粗脂肪均无显著影响(P>0.05);晶体组肌肉粗蛋白含量显著提高(P<0.05),螯合组无显著改变(P>0.05);两种蛋氨酸没有改变大口黑鲈肌肉组织学结构和TPA数据(P>0.05)。两种蛋氨酸都提高了大口黑鲈血清AKP、T-SOD和T-AOC活性(P<0.05);同时,添加锌螯合蛋氨酸降低了大口黑鲈血清MDA含量(P<0.05)。综上所述,酶解羽毛粉替代部分鱼粉的饲料中添加蛋氨酸可以提高大口黑鲈的生长性能,同时不改变其肌肉品质,并提高大口黑鲈抗氧化能力。

饲料中添加桑枝生物炭对大口黑鲈生长性能及抗氧化指标的影响

为探究饲料中添加桑枝生物炭对大口黑鲈(Micropterus salmoides)生长性能、体成分、血清生化及抗氧化指标的影响,本实验随机选取480尾初始体质量为(3.31±0.01)g的大口黑鲈分为4组,每组4个重复,每个重复30尾,在42 d饲养期中分别投喂添加桑枝生物炭0、10、20和40 g/kg的实验饲料,养殖结束后统计各组总重及总尾数,计算成活率、增重率、饲料系数和特定生长率等生长性能,检测血清生化指标及血清、肝脏抗氧化指标。结果显示:饲料中添加桑枝生物炭对大口黑鲈的生长性能无显著影响,粗脂肪含量随着桑枝生物炭添加量的增加而呈显著下降趋势。桑枝生物炭组大口黑鲈血清尿素、甘油三酯、胆固醇和谷草转氨酶含量显著降低。大口黑鲈的血清总抗氧化能力(T-AOC)呈先升后降趋势,血清丙二醛(MDA)含量随桑枝生物炭的添加而显著下降。各桑枝生物炭添加组肝脏T-AOC和SOD活性显著高于对照组,桑枝生物炭添加组肝脏MDA含量显著降低,20 g/kg组肝脏MDA含量最低。20 g/kg组血清及肝脏谷胱甘肽过氧化物酶(GSH-Px)活性显著增加。综合生长性能和抗氧化指标评价,大口黑鲈饲料中的桑枝生物炭添加水平为10~20 g/kg时效果较好。

蚯蚓渣粉替代鱼粉对大口黑鲈生长和肌肉品质的影响

为探究蚯蚓渣粉替代鱼粉日粮对大口黑鲈(Micropterus salmoides)生长性能和肌肉品质的影响,实验设计蚯蚓渣粉替代不同比例鱼粉(0%、10%、20%、30%)的4种饲料,分别记为Control、D10、D20和D30组,进行四个月养殖实验。结果显示,D10组大口黑鲈终末重和特定生长率显著高于Control组,D20组大口黑鲈肌肉保水能力显著高于Control组,D30组大口黑鲈肌肉弹性和回复性显著低于Control组。并且3个实验组大口黑鲈全鱼和肌肉中蛋白质含量和肌纤维面积(1000~5000μm^(2))的百分比显著高于Control组,而碱性磷酸酶(AKP)、谷草转氨酶(GOT)和谷丙转氨酶(GPT)活力无显著性差异。此外,与Control组相比,蚯蚓渣粉替代鱼粉实验组可通过上调肌肉生长相关基因的表达水平来促进肌纤维新生和生长,进而改善肌肉品质。D20组肌肉保水能力、蛋白质含量、肌纤维面积(1000~5000μm^(2))和胰岛素样生长因子1基因表达量均显著高于Control组,其肌肉弹性和回复性均显著低于Control组。因此,综合分析生长性能及肌肉品质结果,建议大口黑鲈日粮中蚯蚓渣粉替代鱼粉的最适替代比例为20%。

发酵豆粕对加州鲈生长性能的影响

该试验旨在探究不同水平的发酵豆粕对加州鲈(Micropterus salmoides)生长性能的影响,确定发酵豆粕的最适添加水平。试验选择375尾体重约为5g的加州鲈,按照单因素试验设计原则,将其均匀分为5个处理组,每组3个重复,每个重复25尾加州鲈。各组加州鲈分别投喂含有0%(对照组)、2.5%、5%、10%和20%发酵豆粕的试验饲料。试验周期为60 d。试验结束后,检测各组加州鲈的生长性能。结果显示,与对照组比较,加州鲈投喂含有10%的发酵豆粕的饲料可以显著提高试验末重和特定生长率(P<0.05),投喂含5%、10%和20%发酵豆粕的饲料可以显著提高增重率(P<0.05)。研究表明,加州鲈投喂适量的发酵豆粕可以提高其生长性能,综合各项数据,发酵豆粕的最适添加量为10%。

大宗淡水鱼坑塘设置网箱养殖大口黑鲈试验

在河北地区采用在大宗淡水鱼坑塘中设置网箱养殖大口黑鲈(Micropterus salmoides)的模式,4月份网箱放养大口黑鲈鱼种75尾/m^(2),规格126~158 g/尾;10月份网箱产量41.44 kg/m^(2),平均规格595 g/尾,成活率92%,饲料系数1.33,利润294.48元/m^(2),投入与产出比1∶1.32。网箱外坑塘大宗淡水鱼鱼种平均产量11115 kg/hm^(2),饲料系数为1.08。该模式当年投放大规格大口黑鲈鱼种,可当年养成,当年销售见效益。