n-3/n-6 HUFA对大菱鲆幼鱼生长性能、全鱼脂肪酸组成和血清生化指标的影响

为探讨饲料中不同n-3/n-6高不饱和脂肪酸(HUFA)对大菱鲆幼鱼生长性能、全鱼脂肪酸组成和血液生化指标的影响,配制了6种不同n-3/n-6 HUFA(D1:29.54,D2:23.04,D3:18.97,D4:9.06,D5:6.86,D6:3.87)的实验饲料。以大菱鲆幼鱼(12.18±0.01)g为研究对象,在循环水养殖系统中开展了为期8周的养殖实验。实验共分6组,每组3个重复,每个重复35尾鱼。结果显示:饲料中n-3/n-6 HUFA对大菱鲆幼鱼的成活率(SR)无显著影响;增重率(WGR)、特定生长率(SGR)和蛋白质效率(PER)呈先上升后下降趋势且D6组的显著低于其他各组,D2组蛋白质效率显著高于其他各组。全鱼粗蛋白和灰分均呈先上升后下降趋势;D6组肌肉粗蛋白和灰分显著低于其他各组。全鱼ARA含量随着n-3/n-6 HUFA的下降呈上升趋势;全鱼中EPA、DHA、n-3/n-6多不饱和脂肪酸(PUFA)和n-3/n-6 HUFA均随着饲料中n-3/n-6 HUFA的下降呈下降趋势。血清中酸性磷酸酶(ACP)和超氧化物歧化酶(SOD)随着n-3/n-6 HUFA的变化呈上升趋势;溶菌酶(LZM)和总抗氧化能力(T-AOC)呈先上升后下降的趋势,溶菌酶在D2组达到最大值,总抗氧化能力在D3组达到最大值。综上所述,饲料中n-3/n-6 HUFA在适宜范围(18.97~23.04)显著提高了实验鱼的生长性能和非特异性免疫力,改变了鱼体组织的常规成分和脂肪酸组成。     

饲料n-3HUFA水平对褐菖鲉血清生化指标、主要脂代谢酶活力及抗氧化能力的影响

研究饲料中n-3HUFA对褐菖鲉(Sebastiscus marmoratus)血清生化指标、主要脂代谢酶活力以及抗氧化能力的影响。以鱼粉、豆粕、酪蛋白为蛋白源,不同比例鱼油与大豆油的混合油为脂肪源,配制n-3HUFA含量分别为0.36%、1.02%、1.82%、2.65%以及3.70%的5种饵料(依次编号为A、B、C、D和E)。实验选用平均初始体重为31.47±0.23 g的褐菖鲉幼鱼225 ind,随机分成5组(每组3个平行,每个平行15 ind),实验周期60 d。研究结果表明:(1)不同n-3HUFA含量的饲料对褐菖鲉血清中的总胆固醇(CHO)以及低密度脂蛋白(LDL-C)含量有显著的影响(P<0.05)。随着饲料中n-3HUFA含量的升高,褐菖鲉血清中的CHO以及LDL-C呈逐渐升高的趋势(P<0.05)。高密度脂蛋白(HDL-C)随饲料中n-3HUFA含量的升高呈现上升的趋势(P>0.05),血清甘油三酯(TG)含量在各组之间没有显著差异(P>0.05);(2)饲料n-3HUFA水平对肝脏脂肪酸合成酶的活力有显著影响,随着饲料中n-3HUFA含量的升高,褐菖鲉肝脏脂肪酸合成酶活力呈现逐渐上升的趋势(P<0.05),脂蛋白酶活力和肝酯酶活力虽均呈现上升趋势,但各组间没有显著差异(P>0.05);(3)饲料n-3HUFA水平对褐菖鲉肝脏丙二醛(MDA)以及总抗氧化能力(T-AOC)有显著的影响(P<0.05),肝脏超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活力随饲料中n-3HUFA水平的升高呈现上升的趋势(P>0.05),血清中SOD以及CAT活力随n-3HUFA水平升高呈逐渐上升趋势(P>0.05)。     

饲料n-3 HUFA水平对珍珠龙胆石斑鱼幼鱼生长、免疫力及相关基因表达和抗病力的影响

本实验旨在研究饲料中不同n-3高不饱和脂肪酸(HUFA)水平对珍珠龙胆石斑鱼幼鱼生长性能、非特异性免疫、免疫相关基因表达及对抵抗哈维氏弧菌能力的影响。配制n-3 HUFA水平分别为0.65%(对照组)、1.00%、1.35%、1.70%、2.05%和2.40%的6种等氮等脂的实验饲料,投喂初始体质量为(12.06±0.01) g的珍珠龙胆石斑鱼幼鱼8周。结果显示:①饲料n-3 HUFA水平对饲料系数(FCR)、存活率(SR)、肝体比(HSI)和肥满度(CF)均无显著性影响;1.35%组增重率(WGR)和特定生长率(SGR)显著高于2.40%组。②1.00%组的体粗脂肪含量显著低于1.70%和2.40%组。③攻毒前,1.35%和1.70%组血清超氧化物歧化酶(SOD)、过氧化氢酶(CAT)的活性和补体C3的浓度显著高于对照组。攻毒后,血清CAT、谷胱甘肽过氧化物酶(GSH-Px)、溶菌酶(LZM)活性和C3含量急剧上升,SOD活性显著下降。攻毒前,2.40%组肠道TLR22和MyD88 mRNA的表达量显著增加,2.05%组TNF-α和IL-1β的表达量显著高于1.00%和1.35%组;此外,1.70%组肾脏TLR22和IL-1β的表达量显著低于对照组。攻毒后,1.35%组肠道MyD88 mRNA的表达量显著高于1.00%和1.70%～2.40%组,1.70%组TNF-α和IL-1β的表达量有最小值;1.70%组肾脏IL-10的表达量显著高于其他各组,而IL-1β的表达量呈相反趋势,显著低于2.40%组。研究表明,适宜的饲料n-3 HUFA(1.47%～1.70%)可以提高珍珠龙胆石斑鱼的生长性能和非特异性免疫力,并抑制促炎基因的表达。     

n-3/n-6 HUFA对许氏平鲉幼鱼生长、体组成及组织脂肪酸组成的影响

为研究饲料n-3/n-6高不饱和脂肪酸(HUFA)对许氏平鲉幼鱼生长、体组成及组织脂肪酸组成的影响,配制了6种n-3/n-6 HUFA(D1:14.28,D2:9.26,D3:5.66,D4:3.06,D5:2.02,D6:1.50)的等氮等脂的实验饲料。以许氏平鲉幼鱼(36.30±0.03) g为研究对象,在网箱中养殖65 d,分为6实验组,每组设3个重复,每个重复30尾鱼。结果发现:①饲料n-3/n-6 HUFA对许氏平鲉幼鱼的成活率无显著影响。随着n-3/n-6 HUFA降低,幼鱼增重率呈先上升后下降趋势,饲料系数呈相反趋势,D2和D3组的增重率显著高于各组。②全鱼和肌肉粗脂肪含量呈先上升后下降趋势,分别在D2、D3组达到最大值。肝脏粗脂肪含量呈先下降后上升趋势,D2组显著小于其他各组。③各组织C20:4n-6含量随n-3/n-6 HUFA的降低均呈上升趋势,而C20:5n-3、C22:6n-3和n-3/n-6 HUFA整体呈下降趋势。④鱼体脂肪酸组成受饲料影响程度由大到小依次为腹脂、肌肉、全鱼、肝脏,且各组织C20:5n-3与饲料C20:4n-6均呈显著负相关。研究表明,在本实验条件下,饲料中适宜比例(5.66～9.26)的n-3/n-6 HUFA显著提高实验鱼的生长,改变体组成及组织脂肪酸组成,以增重率和饲料系数作评价指标,经一元二次回归分析得许氏平鲉幼鱼饲料中n-3/n-6 HUFA的适宜比例分别是8.93和8.70。     

n-3高不饱和脂肪酸对黑鲷幼鱼生长及脂肪代谢的影响

研究了饲料中不同水平n-3 HUFA(0.79%,0.83%,0.85%,0.88%,0.92%,0.94%;DHA/EPA=2.8/1)对黑鲷幼鱼生长及脂肪代谢的影响.结果显示:(1)黑鲷幼鱼肝体指数(HSI)及腹脂率(IPF ratio)随饲料中n-3 HUFA含量的增加而减小,且于0.92%和0.94%组时显著低于其他各组;脂肪细胞直径呈减小趋势,其中0.94%组显著小于0.85%组;肌肉脂肪含量受n-3 HUFA的影响显著,于0.88%组时达到最低.各组全鱼水份和脂肪含量差异不显著(P＞0.05).肝脏、肌肉及腹腔脂肪组织饱和脂肪酸(∑SFA)和C16:0含量均随饲料n-3HUFA水平增加呈下降趋势,而∑n-3 HUFA呈显著上升趋势.各组织中DHA/EPA不受饲料脂肪酸组成的影响.以增重率为参考指标,二次回归分析结果表明,黑鲷幼鱼[(8.08±0.09)g]获得最佳增重时对饲料中n-3 HUFA的需要量为0.87%DM;(2)黑鲷幼鱼肝脏脂肪酸合成酶(FAS)活性及基因表达水平均在n-3 HUFA＞0.92%时有显著下降(P＜0.05);腹腔脂肪激素敏感脂肪酶(HSL)活性及基因表达水平均随饲料中n-3 HUFA的添加呈升高趋势(P＜0.05),且高含量n-3 HUFA(0.94%)可使HSL活性增加近一倍.结果表明,饲料中n-3HUFA通过同步调控脂肪合成与分解两个过程影响黑鲷幼鱼脂肪代谢.     

饲料不同钙磷比对三疣梭子蟹幼蟹生长性能、矿物质沉积和能量代谢的影响

为研究饲料中不同钙磷比对三疣梭子蟹幼蟹生长性能、血清生化、矿物质沉积和能量代谢的影响,配制5种等氮等脂(46%粗蛋白和7%粗脂肪)钙磷比分别为1.00∶2.00、1.00∶1.50、1.00∶1.00、1.00∶0.75和1.00∶0.50的实验饲料。选择初始体质量为(12.82±0.37) g的梭子蟹150只,随机分成5组(每组3个重复,每个重复10只),进行为期8周的养殖实验。结果显示,钙磷比为1.00∶1.00和1.00∶0.75的饲料,其特定生长率(SGR)和饲料效率(FER)显著高于其他组。钙磷比为1.00∶0.50饲料组幼蟹血淋巴的谷草转氨酶(GOT)显著高于其他组,碱性磷酸酶(AKP)和谷丙转氨酶(GPT)活性随着饲料钙磷比的增加呈上升的趋势。幼蟹肝胰腺、肌肉和甲壳中的磷含量随着钙磷比的升高呈下降的趋势,且钙磷比1.00∶2.00组幼蟹磷含量显著高于1.00∶0.50组。钙磷比1.00∶1.50和1.00∶1.00组幼蟹肝胰腺ATP含量显著高于其他饲料组。幼蟹肝胰腺己糖激酶(HK)和琥珀酸脱氢酶(SDH)的活性随饲料钙磷比的升高呈先升高后下降的趋势,当钙磷比为1时,梭子蟹肝胰腺的HK和SDH酶活性最高。此外,钙磷比1.00∶1.00组显著上调了梭子蟹肝胰腺电子传递链相关基因(nd1、sdhc、cytb和coxⅡ)的表达水平,当钙磷比为1.00∶0.75时,显著上调了幼蟹肝胰腺线粒体能量代谢相关基因(ATPase6、sirt3和nrf1)的表达量。研究表明,本实验条件下,以增重率为评价指标,通过回归模型得到梭子蟹最适钙磷比为1.06～1.26,在此范围内能促进三疣梭子蟹幼蟹的生长、维持组织的最适磷沉积以及很好地促进能量的产生。     

饲料不同脂肪和脂肪酶水平对细鳞鲑生长性能、血清生化指标和肝脏抗氧化性能的影响

本实验旨在研究饲料不同脂肪和脂肪酶水平对细鳞鲑(Brachymystax lenok)生长性能、血清生化指标和肝脏抗氧化性的影响。采用2×3双因素实验设计,配制2个脂肪水平(180和220 g/kg)和3个脂肪酶水平(0、2500和5000 U/kg)的6种实验饲料,即C-0、C-2500、C-5000和H-0、H-2500、H-5000。挑选270尾初始体重为(7.34±0.16) g的细鳞鲑,随机分为6个组,每组3个重复,每个重复15尾鱼。各组实验鱼分别投喂6种不同的实验饲料,养殖63 d。结果显示,不同脂肪含量和脂肪酶水平对终末平均体重存在极显著交互作用(P<0.01),对增重率(WGR)和特定生长率(SGR)存在显著的交互作用(P<0.05),脂肪与脂肪酶二者均对机体的生长性能产生影响,其中,同一脂肪水平,鱼体重、WGR和SGR均以C-5000组最高。H-0、H-2500、H-5000组血液中的谷丙转氨酶(ALT)分别低于C-0、C-2500、C-5000组,其中,H-0、H-5000与C-0、C-5000组存在显著差异(P<0.05);H-0、H-2500、H-5000组的低密度脂蛋白胆固醇(LDL-C)分别高于C-0、C-2500、C-5000组,其中,H-0、H-2500与C-0、C-2500组存在显著差异(P<0.05)。随着脂肪酶水平升高,肝脏中谷胱甘肽过氧化物酶(GPX)水平提高,且相同脂肪酶水平的220 g/kg组GPX高于180 g/kg组。综上所述,在脂肪水平为183.7 g/kg、脂肪酶添加量为5000 U/kg时,可以明显改善细鳞鲑幼鱼的生长和抗氧化性能。     

发酵豆粕部分替代鱼粉后凡纳滨对虾对赖氨酸的需求量

为研究发酵豆粕部分替代鱼粉后,饲料赖氨酸(Lys)水平对凡纳滨对虾生长、体组成与血清生化指标的影响,进而确定凡纳滨对虾对饲料赖氨酸的需要量,实验在基础饲料中分别添加0%、0.25%、0.50%、0.75%和1.00%的晶体赖氨酸配制成5种等氮等脂的实验饲料(含粗蛋白41.5%、粗脂肪7.5%),实测各组赖氨酸含量分别为2.43%、2.65%、2.87%、3.06%和3.24%,记为Lys0、Lys25、Lys50、Lys75和Lys100。选择初始体质量为(2.0±0.1) g的凡纳滨对虾随机分为5组,每组3个重复,每个重复50尾虾,在室内水泥池中进行为期56 d的养殖实验。结果显示,随着饲料赖氨酸水平的提高,凡纳滨对虾的增重率(WGR)和特定生长率(SGR)先升高后降低,在Lys75组达到最高,且该组饲料系数(FCR)最低;凡纳滨对虾成活率不受饲料赖氨酸水平的影响。Lys75组对虾肌肉粗蛋白和粗脂肪含量最高,而对虾肌肉粗灰分和水分含量则不受饲料赖氨酸水平的影响;肌肉必需氨基酸中的赖氨酸、缬氨酸(Val)、异亮氨酸(Ile)、苯丙氨酸(Phe)随着饲料赖氨酸水平的提高呈先升高后降低的趋势。随着饲料赖氨酸水平的提高,血清中谷丙转氨酶(ALT)、谷草转氨酶(AST)活性呈先升高后降低的趋势,甘油三酯(TG)含量呈逐渐升高的趋势,Lys75组超氧化物歧化酶(SOD)活性显著低于其他各组。对SGR、FCR与饲料赖氨酸水平进行二次曲线拟合分析,结果显示,凡纳滨对虾对赖氨酸的最适需求量分别为2.88%(饲料粗蛋白的6.94%)、2.89%(饲料粗蛋白的6.96%)。本实验通过探讨凡纳滨对虾在该饲料配方条件下对赖氨酸的最适需求量,旨在为其大规模配合饲料的生产提供参考。     

饲料蛋白质水平与投喂频率对吉富罗非鱼幼鱼生长及部分生理生化指标的影响

为探讨饲料蛋白质水平与投喂频率对罗非鱼生长及生理健康的影响,采用2×3双因子实验,研究饲料蛋白质水平(36.27%和26.02%)与投喂频率(1、2和3次/d)对吉富罗非鱼幼鱼生长、体成分、血清指标和肝胰脏结构的影响。养殖周期为42 d,结果表明:随饲料蛋白质水平的增加,实验鱼的末体质量(FW)、增重率(WGR)、特定生长率(SGR)、饲料效率(FE)、肥满度(CF)、去内脏全鱼灰分(EWA)、内脏水分(VM)、高密度脂蛋白胆固醇(HDLC)水平显著升高(P0.05),而摄食率(FI)、脏体比(VSI)、饲料成本(FC)、去内脏全鱼粗脂肪(EWF)、内脏粗脂肪(VF)、肝胰脏粗脂肪(HF)显著降低(P0.05);随投喂频率的增加,实验鱼的FW、WGR、SGR、肝体比(HSI)、CF、FC、EWF、VF、HF,血清中的总胆固醇水平(TCHO)、HDLC、低密度脂蛋白胆固醇(LDLC)、总蛋白(TP)、甘油三酯(TGK)水平显著升高(P0.05),而FE、蛋白质效率(PER)、去内脏全鱼水分(EWM)、EWA、VM、肝胰脏水分(HM)显著降低(P0.05)。饲料蛋白质水平和投喂频率对实验鱼的FW、WGR、SGR、VM和HDLC的交互作用显著(P0.05)。投喂26.02%蛋白质水平饲料的实验鱼,肝胰脏细胞肿大变形,呈现透明的空泡化,出现细胞核偏移;而投喂36.27%蛋白质饲料的实验鱼,大多数肝细胞胞浆清晰,可观察到的肝细胞空泡面积较小。综合考虑,饲料蛋白质含量为36.27%是适合吉富罗非鱼幼鱼的,其适宜的投喂频率为2次/d以上,可根据罗非鱼市场情况进行调节。     

养殖细鳞鲑、哲罗鲑及其杂交种肌肉脂肪酸组成与含量的比较

本文分析和比较2龄细鳞鲑Brachymystax lenok、哲罗鲑Hucho taimen及其杂交种肌肉脂肪酸组成与含量。结果表明:在细鳞鲑、哲罗鲑及其杂交种肌肉中均检测到19种脂肪酸,以C_(16:0)、C_(16:1)、C_(18:1)、C_(18:2n)和C_(22:6n-3)为主,未检测到C_(12:0)、C_(22:1)、C_(22:5n-3);三种鱼的饱和脂肪酸含量(∑SFA)差异不显著(P0.05);但三者不饱和脂肪酸含量(∑UFA)差异显著(P0.05),细鳞鲑的不饱和脂肪酸含量显著高于哲罗鲑和杂交种(P0.05),其中多不饱和脂肪酸含量分别为(35.42±1.80)%、(38.46±1.29)%和(40.02±3.65)%,杂交种的多不饱和脂肪酸含量显著高于细鳞鲑和哲罗鲑(P0.05)。研究结果表明,细鳞鲑、哲罗鲑及其杂交种的肌肉多不饱和脂肪酸含量较其他淡水鱼类高,尤其二十碳五烯酸(EPA)和二十二碳六烯酸(DHA)含量,甚至高于野生群体的含量;EPA和DHA的含量取决于饲料营养水平。建议人们多食用鲑鳟鱼类。     

饲料组成对银鲳幼鱼生长率及肌肉氨基酸、脂肪酸组成的影响

研究分析了饲料组成对银鲳(Pampus argenteus)幼鱼特定生长率(SGR)及肌肉氨基酸与脂肪酸组成的影响。实验共设4组不同的饲料组成,依次为饲料A(鱼肉糜)、饲料B(鱼肉糜+配合饲料)、饲料C(鱼肉糜+配合饲料+蛏子肉糜)和饲料D(鱼肉糜+配合饲料+蛏子肉糜+桡足类)。实验用银鲳幼鱼的平均体重为4.80±0.11 g,每组饲料设3重复,实验周期为9周。研究结果显示,不同饲料组成可显著影响银鲳的特定生长率,饲料A组的特定生长率最低,并显著低于其它各饲料组;饲料D组的特定生长率最高,且显著高于饲料B、C组的特定生长率(P<0.05);但饲料B、C组间银鲳特定生长率无显著性差异(P>0.05)。银鲳肌肉氨基酸与脂肪酸的分析结果显示,4组饲料组成对银鲳肌肉氨基酸的组成及含量并无显著性影响(P>0.05),但可显著影响肌肉脂肪酸的组成及含量(P<0.05)。饲料D组的多不饱和脂肪酸(PUFA)、高度不饱和脂肪酸(HUFA)及n-3HUFA含量均分别显著高于饲料A、B和C组(P<0.05),饲料B和C组的PUFA、HUFA及n-3HUFA均分别显著高于饲料A组(P<0.05),但饲料B、C组间并无显著性差异(P>0.05)。综合分析得出,丰富的饲料组成以及饲料中较高的HUFA含量均有利于银鲳幼鱼的生长。     

Requirements for n-3 highly unsaturated fatty acids in feeding juvenile Iranian sturgeon (<Emphasis Type="Italic">Acipenser persicus</Emphasis>) and its effects on growth,carcass quality,and fatty acid composition

A 60-day feeding experiment was carried out on juvenile Iranian sturgeon (Acipenser persicus) to evaluate the effects of different percentages of canola oil and fish oil containing n-3 highly unsaturated fatty acids (n-3 HUFA) on fish growth and fatty acid composition. The requirement for n-3 HUFA of juvenile Iranian sturgeon (48.4 ± 1.98 g) was studied by feeding the fish with various diets containing six different percentage of n-3 HUFA ranging from 1.56 to 17.25 (% of total fatty acids). Neither the weight gain, feed conversion ratio, condition factor, specific growth rate nor the protein efficiency ratio showed any significant differences between the dietary treatments nor in the body composition of juvenile Iranian sturgeon (P > 0.05); also there were no significant difference with respect to the effect of the dietary treatment (P > 0.05) on the blood parameters, for the content of plasma protein, glucose, cholesterol, and triglyceride. The fatty acid composition of the carcass of the Iranian sturgeon fed with the diets containing various levels of n-3 HUFA was reflected by the dietary fatty acid composition. The content of n-3 HUFA in the fish increased with an increase in dietary n-3 HUFA levels. The results indicate that the dietary n-3 HUFA had no effect on the growth of juvenile Iranian sturgeon.     

饲料不同n-3/n-6脂肪酸比值对日本沼虾生长、虾体组分、血清抗氧化及相关基因表达的影响

为探讨饲料中n-3/n-6脂肪酸比值对日本沼虾生长性能、虾体肉质及血清抗氧化能力的影响,设计了5种不同n-3/n-6脂肪酸比值(D1:0.29、D2:0.56、D3:1.02、D4:2.20、D5:8.52)的等氮等脂饲料,进行了8周养殖实验,每组设4个重复,每个重复45尾虾。结果显示,饲料n-3/n-6脂肪酸比值对日本沼虾的存活率(SR)无显著影响;日本沼虾增重率(WGR)和特定生长率(SGR)随饲料脂肪酸比值的增加先升后降,D3组最高且显著高于D1组。饲料n-3/n-6脂肪酸比值对虾体粗脂肪(CF)和粗蛋白(CP)影响显著,D4组虾体粗脂肪显著高于其他各组;D3组虾体粗蛋白显著高于D2、D4和D5组。虾体肌肉脂肪酸比值受饲料脂肪酸比值的影响,肌肉中n-3/n-6脂肪酸比值与饲料中n-3/n-6脂肪酸比值存在显著的正相关关系。血清超氧化物歧化酶(SOD)在D5组达到最高且显著高于D1、D2和D3组,但与D4组差异不显著;D3组谷胱甘肽过氧化物酶(GSH-Px)最高且显著高于其他各组;D5组血清丙二醛(MDA)含量显著高于D1和D3组。饲料脂肪酸比值对日本沼虾肝胰腺抗氧化基因表达影响显著,D4组Hsp60表达量最高且显著高于D5组,但与D1、D2和D3组差异不显著;D2组Hsp70和Toll表达量最高且显著高于其他各组;D5组Myd88表达量最高且显著高于其他各组。综上所述,饲料中n-3/n-6脂肪酸比值为1.02～2.20,可以显著提高日本沼虾的生长性能和非特异性免疫力。     

Requirement of n-3 long chain polyunsaturated fatty acids for European sea bass (Dicentrarchus labrax) juveniles: growth and fatty acid composition

European sea bass juveniles (14.4±0.1 g mean weight) were fed diets containing different levels of fish oil then of n-3 highly unsaturated fatty acids (n-3 HUFA) for 12 weeks. The fish performance as well as fatty acid (FA) composition of neutral and polar lipids from whole body after 7 and 12 weeks feeding were studied. The requirements of juvenile sea bass for n-3 highly unsaturated fatty acids (n-3 HUFA) were studied by feeding fish diets containing six different levels of n-3 HUFA ranging from 0.2% to 1.9% of the diet, with approximately the same DHA/EPA ratio (1.5:1).

The growth rate at the end of the trial showed significant differences. Fish fed low dietary n-3 HUFA (0.2% DM of the diet) showed significantly lower growth than the diet 3 (0.7%), then no further improvement (P>0.05) of growth performance was seen by elevating the n-3 HUFA level in the diet up to 1.9% (diet 6). No difference in feed efficiency, protein efficiency ratio or protein retention was observed among treatments, nor in protein and total lipid content. However, the n-3 HUFA levels in diets highly influenced fish fatty acid composition in neutral lipid, while polar lipid composition was less affected. Comparison of polar lipid content after 7 or 12 weeks indicated that DHA remained stable at the requirement level, while arachidonic acid decreased with time. Results of this experiment suggest that the requirement for growth of n-3 HUFA of juvenile sea bass of 14 g weight is at least 0.7% of the dry diet.     

n-3/n-6长链多不饱和脂肪酸对大菱鲆幼鱼脂肪沉积、脂肪吸收及代谢相关酶活性和血清生化指标的影响

为探讨饲料中不同n-3/n-6长链多不饱和脂肪酸(LC-PUFA)对大菱鲆(Scophthalmus maximus)幼鱼生长性能及饲料利用、体组成和消化酶的影响,配制了6种不同n-3/n-6 LC-PUFA比值(29.54,D1组;23.04,D2组;18.97,D3组;9.06,D4组;6.86,D5组;3.87,D6组)的实验饲料。以大菱鲆幼鱼[(12.18?0.01)g]为研究对象,在循环水养殖系统中开展了为期56 d的养殖实验。结果显示,n-3/n-6 LC-PUFA对大菱鲆幼鱼的成活率(SR)无显著影响(P0.05);增重率(WGR)随着n-3/n-6 LC-PUFA的降低呈先上升后下降趋势,D6组显著低于其他各组(P0.05);脂肪沉积率随着饲料中n-3/n-6 LC-PUFA的降低呈下降趋势,且D6组达到最小值,为14.80,显著低于其他各组(P0.05)。随着饲料中的变化,胰蛋白酶的活性呈先增强后减弱的趋势,且在D4组时达到最大值;脂肪酶活性呈上升趋势。随着饲料中n-3/n-6 LC-PUFA的变化,脂肪酸合成酶活性呈先上升后下降的趋势,最高值为D4组,显著高于其他各组(P0.05);葡萄糖-6-磷酸脱氢酶的酶活呈先上升后下降的趋势,D3组为最大值,显著高于其他各组(P0.05)。随着饲料中n-3/n-6 LC-PUFA的降低,谷草转氨酶呈先上升后下降的趋势;总蛋白、白蛋白和高密度脂蛋白胆固醇均随着饲料n-3/n-6LC-PUFA的变化呈先上升后下降的趋势,均在D5组时达到最大值。研究表明,饲料中n-3/n-6LC-PUFA的比例降低会导致大菱鲆幼鱼的脂肪沉积率降低。     

Effects of a diet lacking HUFA on lipid and fatty acid content of intestine and gills of male gilthead seabream (Sparus aurata L.) broodstock at different stages of the reproductive cycle

A feeding experiment was carried out to determine the effect of a diet lacking n-3 and n-6 highly unsaturated fatty acids (HUFA) on lipid and fatty acid content in intestine and gills of male gilthead seabream (Sparus aurata L.) broodstock at different stages of the reproductive cycle: November (pre-spermatogenesis), March (spermatogenesis), and June (post-spermatogenesis). For this purpose, gilthead seabream broodstock were fed either a control diet (C) or an n-3 and n-6 HUFA-deficient diet (D). The results showed no changes in fatty acid content of polar lipids of intestine and gills from fish fed diet C at different stages of the reproductive cycle. However, significant changes were observed in the fatty acid content of neutral lipids in intestine but not in gills in this group. Thus, between November and March, saturates and n-3 HUFA decreased while monoenes increased. In June, the contents of these fatty acids had returned to their initial values (November). Moreover, in fish fed diet D, the fatty acid content of neutral lipid changed in both intestine and gills. In intestine NL, a decrease in saturates and n-3 HUFA and an increment in monoenes were observed from November to June. In gills, a decrease was also observed in n-3 HUFA from NL along the cycle. Nevertheless, n-6 HUFA content remained unchanged. These results show both tissue specificity in seasonal mobilization of fatty acids linked to reproductive processes and the influence of dietary fatty acids on body composition.     

Effects of dietary lipid levels on the growth, digestive enzyme, feed utilization and fatty acid composition of Japanese sea bass (Lateolabrax japonicus L.) reared in freshwater

Triplicate groups of 40 Japanese sea bass Lateolabrax japonicus reared in freshwater (average weight, 9.52±0.47 g) were fed with six isonitrogenous (∼46% crude protein) diets containing 6%, 8%, 10%, 12%, 14% or 16% lipid for 10 weeks respectively. The results showed that the maximum weight gain (WG), specific growth rate (SGR), feed intake (FI) and protein efficiency ratio (PER) all occurred at the 10% lipid level ( P <0.05) and growth depression occurred when the dietary lipid level was over 12%. Whole body and liver lipid concentrations were enhanced with the increase in the dietary lipid levels, but the muscle lipid content did not significantly change with the increase in the dietary lipid levels. Both liver pepsin and trypsin activities increased with dietary lipid levels ranging from 6% to 10%, and then decreased with a further increase in the dietary lipid content. Liver lipase activities showed a positive correlation with dietary lipid levels, but amylase activities were not markedly influenced by dietary lipid levels. High proportions of 18:1n-9, 20:1n-9, eicosapentaenoic acid (20:5n-3; EPA), 22:1n-11 and docosahexaenoic acid (22:6n-3; DHA), and low concentrations of n-6 fatty acids, particularly 18:2n-6 occurring in the liver and muscle, to some extent, reflected the fatty acid composition in experimental diets.     

胆汁酸对草鱼(Ctenopharyngodon idellus)的生长性能、肌肉营养成分及消化酶活性的影响

为研究胆汁酸对草鱼(Ctenopharyngodon idellus)生长性能、肌肉营养成分及消化酶活性的影响,选取初始体重为(13.11±0.58)g的草鱼540尾,随机分成6个实验组,分别饲喂胆汁酸添加量为0、75、150、225、300、375 mg/kg的等氮等能饲料(粗蛋白含量34.56％,总能13.54 kJ/g),养殖时间为60 d.结果显示,随着胆汁酸浓度的增加,草鱼的增重率(WGR)、特定生长率(SGR)均呈先上升后下降的变化趋势,且均在胆汁酸添加量为300 mg/kg时达到最大值(分别为281.18％和2.23％/d);饲料系数(FCR)则呈先下降后上升的趋势,且在胆汁酸添加水平为225 mg/kg时达最低值(1.26).由二次回归方程可知,WGR、SGR、FCR等生产性能最优时,胆汁酸添加水平分别为222.15、265.00、242.86 mg/kg.实验鱼肌肉粗脂肪含量随胆汁酸添加量的增加而呈先下降后趋于稳定的变化趋势,粗蛋白质含量则呈先上升后降低的变化趋势.肠道各段及肝胰脏的消化酶活性均随胆汁酸添加量的增加呈先升高后下降的趋势.由此说明,适量的胆汁酸能提高草鱼生长性能,促进其脂肪代谢,降低机体脂肪沉积,改善其肌肉品质.本研究考虑到草鱼消化酶活性、肌肉品质及生长性能等因素,其饲料中胆汁酸适宜的添加量为222.15-265.00 mg/kg.     

Dietary fatty acid composition influences swimming performance in Atlantic salmon (Salmo salar) in seawater

Swimming performance was measured in Atlantic salmon (Salmo salar, L.) fed one of four isonitrogenous and isoenergetic experimental diets, in which the supplemental lipid (25% of diet) originated either solely from menhaden oil (rich in highly unsaturated fatty acids of the n-3 series; n-3 HUFA), or from different proportions of this oil and canola oil (rich in 18-carbon unsaturated fatty acids).The results indicate that dietary fatty acid composition influenced swimming performance in Atlantic salmon through changes in maximum swimming speed (U_crit). Salmon fed a diet in which menhaden oil furnished all of the supplemental lipid had a significantly lower U_crit than those fed a diet in which the supplemental lipid was an equal blend of menhaden and canola oil. Furthermore, there was a highly significant linear relationship between dietary and/or muscle levels of particular fatty acids or groups of fatty acids and U_crit.There was a negative relationship between dietary n-3 HUFA content and U_crit, but there was no relationship between U_crit and muscle n-3 HUFA content nor between U_crit and the levels of the eicosanoids thromboxane A₂ and prostacyclin, or of their ratio, in the heart and gills of fatigued salmon. These results indicate that the differences in exercise performance were not a result of differences in n-3 HUFA metabolism amongst the dietary groups.Indeed, although there was a highly significant positive relationship between U_crit and total n-6/n-3 fatty acid ratio of muscle lipids, this was largely due to the associated positive relationship between U_crit and content of the most common n-6 fatty acid in muscle lipids, linoleic acid. There was also a significant positive relationship between content in muscle lipids of the most prominent fatty acid in canola oil, oleic acid, and U_crit. It is suggested that metabolism of these 18-carbon unsaturated fatty acids accounts for the effects of the diets on exercise performance.