饲料磷水平对吉富罗非鱼营养代谢和肠道微生物的影响

为研究饲料不同磷水平对吉富罗非鱼营养代谢及肠道微生物的影响,实验以磷酸二氢钙作为磷源,配制成总磷含量为0.26%(低磷组)、0.81%(适磷组)和1.51%(高磷组)的3组等氮等能饲料,每种饲料为一个处理,每个处理设置4个重复,每个重复30尾鱼,用3种饲料分别饲喂初始体重为(8.42±0.09) g的吉富罗非鱼8周。结果显示,适磷组吉富罗非鱼的增重率和特定生长率显著高于低磷组和高磷组,饲料系数在适磷组最低。脏体比、肝体比和肥满度随饲料磷水平的升高呈逐渐下降趋势。随着饲料磷水平的增加,吉富罗非鱼干物质、粗蛋白、粗脂肪、磷的表观消化率显著降低。对筛选到的差异代谢物进行KEGG注释和富集分析发现,饲料磷缺乏时下调的差异代谢物主要富集的代谢通路为氰胺酸代谢、葡萄糖酸酯的生物合成、丙氨酸、天冬氨酸和谷氨酸代谢,上调的差异代谢物主要富集的代谢通路为脂肪酸合成;当饲料磷过量时下调的差异代谢物主要富集代谢通路为精氨酸和脯氨酸代谢、苯丙酸的生物合成,上调的差异代谢物主要富集代谢通路为氨基糖和核苷酸糖的代谢。Ace、Chao1和Shannon指数表明,吉富罗非鱼肠道菌群丰度和多样性随着饲料磷水平的升高呈现...     

甘露寡糖对高糖饲喂下尼罗罗非鱼肌肉品质的影响

甘露寡糖是一种新型饲料添加剂，它具有保护肠道健康和降血糖的功能。然而，甘露寡糖对于鱼类肌肉品质的影响并无系统性报道。为此，本实验选择均重为2g左右的健康尼罗罗非鱼幼鱼315尾，随机分成对照组（Control，糖含量为35%）、高糖处理组（HC，糖含量为45%）和高糖饲料中添加甘露寡糖处理组（HM，糖含量为45%，甘露寡糖添加量为0.5%），每组3缸，每缸35尾，投喂10周后，测定其生长指标、肌肉营养成分和质构特性等相关指标。结果显示，与对照组相比，HC组尼罗罗非鱼肝体比，肌肉内聚性，肌纤维数量、肌苷酸含量、鲜味氨基酸占比、支链氨基酸/芳香族氨基酸比例、甘油三酯含量以及可促进肌肉生长的钙蛋白酶抑制蛋白基因CAST 相对表达量均显著升高；肌肉硬度、胶着性、咀嚼性、肌纤维直径、蒸煮损失，必需氨基酸占比以及在肌纤维的分化中起着重要作用的MyoG基因 相对表达量以及脂肪酸、甘油二酯和磷脂酰肌醇含量显著降低。与HC组相比，HM组尼罗罗非鱼的肌肉弹性、必需氨基酸占比，脂肪酸和甘油二酯含量以及CAST基因相对表达量显著增加；肌肉粘力、肌纤维数量、肌苷酸含量，磷脂酰乙醇胺和磷脂酰胆碱含量以及MyoG基因相对表达量均显著降低。与对照组相比，HM组尼罗罗非鱼增重率和肌肉内聚性，支链氨基酸/芳香族氨基酸比例，甘油三酯和脂肪酸含量显著增加；肝体比，肌肉硬度、咀嚼性以及磷脂含量均显著降低。上述结果表明，高糖饲喂可以使罗非鱼肌肉的保水能力增强，其肌肉更嫩更柔软紧密，提升肌肉鲜味，但会降低氨基酸营养价值。在添加甘露寡糖后，可以促进尼罗罗非鱼生长，提高产肉率和肌肉持水力，并且肌肉更加柔软紧密且富有弹性，提高氨基酸营养价值，但是会降低磷脂含量。     

吉富罗非鱼成鱼对饲料中有效磷的需要量

为获得吉富罗非鱼成鱼对饲料中有效磷的需要量,以磷酸二氢钾(KH₂PO₄)为磷源,配制含有效磷水平分别为0.15％(对照组)、0.40%、0.66%、0.91%、1.17%和1.43%的6组等氮等能的半纯化饲料,每组饲料饲喂3个重复,每个重复饲养20尾初始体质量为(184.46±8.13)g吉富罗非鱼,经过9周的饲养后,对生长性能、饲料效率、成活率、全鱼基本营养成分、脊椎骨及鳞片的磷含量进行测定。结果显示,饲料有效磷为0.66％或0.91%时,鱼体增重率和特定生长率较其它各组均显著提高(P<0.05),饲料效率显著高于对照组(P<0.05)。随着饲料有效磷含量的增加,实验鱼体的脏体指数、肝体指数和肥满度均显著降低(P<0.05),成活率无显著性变化(P＞0.05);全鱼粗蛋白、粗灰分及磷含量均显著提高(P<0.05),粗脂肪含量显著下降(P<0.05);脊椎骨和鳞片的粗灰分和磷含量均显著提高(P<0.05)。用抛物线模型拟合特定生长率与饲料有效磷含量,罗非鱼获得最大生长时,对饲料中有效磷需要量为0.85%;分别对全鱼磷含量、鳞片磷含量和脊椎骨灰分含量与饲料有效磷含量进行相关回归分析,罗非鱼对饲料中有效磷需要量分别为0.88%、1.14%、1.23%。     

饲料中有效磷对吉富罗非鱼生长、体组成及生化指标的影响

为探讨饲料中不同有效磷水平对吉富罗非鱼幼鱼生长、体组成及生化指标的影响,以磷酸二氢钙(MCP)为磷源,配制含有效磷(AP)水平分别为0.52%(对照组)、0.61%、0.70%、0.78%、0.87%、0.96%和1.05%的7种等氮等能实用饲料,饲喂初始均重为(29.40±0.15)g的实验鱼。每种饲料设置3个重复,每个重复放25尾鱼,进行56 d的养殖实验。结果表明:饲料AP水平对罗非鱼的增重率(WGR)、特定生长率(SGR)、饲料系数(FCR)和脏体比(VSI)均有显著影响(P<0.05)。以WGR为评价指标,通过二次回归分析得出,罗非鱼饲料的适宜AP水平为0.80%。随饲料AP水平的增加,罗非鱼全鱼总磷和灰分含量显著增加并达到稳定(P<0.05),而全鱼水分含量差异不显著(P>0.05),全鱼和肠系膜、肝脏组织脂肪含量均显著下降(P<0.05)。用折线模型分析全鱼磷和灰分含量,得出罗非鱼幼鱼对饲料AP的需求量分别为0.81%和0.80%。随饲料AP水平的增加,肝脏苹果酸脱氢酶(MDH)、丙酮酸激酶(PK)、脂蛋白脂酶(LPL)和肝酯酶(HL)活性均显著增加(P<0.05)。血清谷丙转氨酶(GPT)活性显著下降(P<0.05),而碱性磷酸酶(AKP)活性显著上升(P<0.05),血清超氧化物歧化酶(SOD)活性呈先升后降趋势,在0.78%水平组达到最大值,而肝脏丙二醛(MDA)含量正好相反,在0.78%水平组最低。综上所述,研究结果表明:吉富罗非鱼(30~150 g)实用饲料的最适有效磷水平为0.80%。     

饲料脂肪对黄颡鱼卵巢脂类代谢以及PI3KCa甲基化和转录水平的影响

为了探究饲料不同脂肪水平对黄颡鱼卵巢脂肪代谢潜在的影响,本研究设计了活体与离体两个实验。活体实验中,分别投喂3组不同脂肪水平的饲料(脂肪含量分别为6.98%、11.34%和15.41%)8周。离体实验中,分离原代黄颡鱼卵母细胞,采用(0、0.2和0.5 mmol/L)3组不同脂肪酸浓度孵育48 h。活体实验结果显示:与6.98%和15.41%脂肪水平组相比,11.34%脂肪水平显著增加黄颡鱼卵巢甘油三酯水平(TG),并上调FAS、G6PD、6PGD和ME的酶活性水平,以及LPL和CD36基因表达水平。与6.98%和11.34%脂肪水平组相比,15.41%脂肪水平组显著升高黄颡鱼的性腺指数(GSI),并上调CPTIA和DNMT3b的基因表达水平,以及PI3KCa启动子-64和-52 CpG位点的甲基化水平,而显著降低PI3KCa的基因表达水平。体外细胞实验显示:与对照组(0)相比,0.5 mmol/L脂肪酸孵育显著增加卵母细胞TG含量,并上调FAS、G6PD和ME酶活水平,以及G6PD和PI3KCa的基因表达水平。同时,与对照组相比,脂肪酸孵育组显著降低CPTIA、ACCb、LPL、CD36、DNMT1以及DNMT3b基因的表达水平。然而,脂肪酸孵育对卵母细胞PI3KCa的启动子甲基化水平没有影响。研究表明,饲料不同脂肪水平影响卵巢TG的合成,可能主要是通过脂肪转运相关基因,并且高脂肪很可能是通过影响黄颡鱼卵巢PI3KCa启动子甲基化水平来影响PI3KCa的表达。而离体条件下,脂肪酸促进卵母细胞TG的合成很可能是通过升高脂肪合成相关基因、降低脂肪分解和转运相关基因来实现,但脂肪酸孵育不通过影响黄颡鱼卵母细胞PI3KCa甲基化水平来影响PI3KCa基因表达。     

杂交鲟幼鱼饲料中有效磷需要量的研究

为研究杂交鲟(Acipenser baerii♀×Acipenser schrenckii♂)幼鱼对饲料中有效磷的需要量,实验以磷酸二氢钙为磷源,配制了有效磷水平分别为0.37%(对照组)、0.65%、0.96%、1.22%和1.48%的5组等氮等能饲料。每组饲料设置3个重复,每个重复22尾鱼,饲喂初重(10.06±0.39)g杂交鲟幼鱼8周。结果显示:(1)饲料中不同有效磷水平对实验鱼的成活率、肝体比、脏体比和肥满度均无显著影响。随饲料有效磷水平增加,实验鱼的增重率和特定生长率呈先升高后趋于平稳的趋势,0.96%、1.22%和1.48%组增重率和特定生长率均显著高于0.37%组和0.65%组;全鱼粗脂肪含量呈降低趋势;饲料效率和蛋白质效率均呈先升高后降低的趋势。(2)不同有效磷水平饲料对全鱼水分、粗蛋白和肌肉水分、粗蛋白、粗脂肪、粗灰分、磷含量均无显著影响。0.96%、1.22%和1.48%组全鱼粗灰分、磷含量和脊椎粗灰分、磷含量均显著高于0.37%组和0.65%组。(3)随饲料有效磷水平增加,实验鱼血清磷含量和碱性磷酸酶活性均呈先升高后趋于平稳的趋势。0.96%、1.22%和1.48%组血清磷含量显著高于0.37%组和0.65%组,对照组的碱性磷酸酶活性显著低于其他组。(4)分别利用折线模型拟合分析实验鱼的增重率、全鱼磷含量和脊椎磷含量与饲料有效磷水平的相关性,得到饲料中适宜有效磷需要量分别为0.93%、1.02%和0.95%。综上所述,建议杂交鲟幼鱼饲料中有效磷添加水平为0.93%~1.02%为最佳。     

饲料中不同水平磷对西伯利亚幼鲟(Acipenser baeri)血浆生化指标的影响

选择平均体重14.5±1.0g,体长16.0±0.5cm的西伯利亚鲟鱼,随机分成11组,每组3个重复,每个重复15尾.试验以磷酸二氢钙为磷源,配成磷含量分别为0.12%、0.20%、0.29%、0.39%、0.48%、0.60%、0.69%、0.80%、0.99%、1.19%和 1.38%的11组饲料,研究饲料中不同水平磷对西伯利亚幼鲟血浆生化指标的影响.结果表明:血浆总蛋白含量、白蛋白含量和球蛋白含量随饲料磷含量的增加呈逐渐上升趋势,在饲料磷含量0.69%时达最高(18.81g/L、6.99 g/L、11.63 g/L),然后随磷水平升高又逐渐下降;当饲料中磷含量大于0.29%时,磷含最对血浆中总胆固醇和甘油三酯含量_尢显著性影响(P>0.05);由血浆蛋白含量可以得出:西伯利亚鲟最适磷需要量为0.69%.     

饲料中补充适宜的大豆纤维改善建鲤的生长性能、生化指标和肠道健康

为评价饲料纤维素在鱼饲料中的营养生理功能,在基础饲料中添加大豆纤维配制成5个纤维水平（1.8%、5.2%、8.8%、12.2%和15.8%）的等氮等脂实验饲料,饲喂建鲤（均重：14.96±0.09 g）8周,从生长、血浆生化、肠道组织学以及肠道微生物等指标研究不同纤维水平对建鲤的影响。结果显示,纤维水平8.8%组建鲤的终末体质量（FBW）、增重率（WGR）、特定生长率（SGR）和蛋白质效率（PER）显著高于其它水平组,而饲料系数（FCR）显著低于其它组。同时发现,纤维水平8.8%组建鲤血浆谷丙转氨酶（ALT）和谷草转氨酶（AST）活性显著低于其它组。随饲料纤维水平的增加,脏体比（VSI）、肝体比（HSI）以及血浆甘油三酯（TG）、胆固醇（TC）和葡萄糖（GLU）含量均显著降低。与对照组（纤维水平1.8%）相比,纤维水平5.2%、8.8%和12.2%组肝脏AMPK、CPT-1活性和PPAR-α含量显著升高。此外,饲料高水平纤维15.8%会损伤建鲤的中肠和后肠组织结构,破环肠道的发育,同时也会显著影响其肠道菌群结构,促进有益微生物的生长。研究表明,饲料中添加适宜大豆纤维能够显著提高建鲤的生长性能,改善机体糖脂代谢。以SGR为指标,建鲤饲料中适宜的纤维水平为9.19%,但高水平纤维（15.8%）则具有一定抑制和破坏作用。     

饲料钙磷水平对宝石鲈生长和体成分的影响

以酪蛋白和明胶作为蛋白源,乳酸钙（Ca-lactate）和磷酸二氢钠(NaH2PO4•2H2O)为钙源和磷源,配制成D1（0.0%钙,0.0%磷）、D2（0.5%钙,0.0%磷）、D3（0.0%钙,0.6%磷）、D4（0.5%钙,0.6%磷）、D5（1.0%钙,0.6%磷）和D6（1.5%钙,0.6%磷）六种等氮等能纯化试验饲料。每组饲料饲喂3个重复,每重复饲养20尾宝石鲈幼鱼,经过室内网箱60天生长试验,探讨在饲料中添加钙磷对宝石鲈幼鱼（初始体质量13.42±0.68g）生长性能、全鱼和肌肉营养成分以及脊椎骨钙磷含量的影响。试验结果表明: 饲料中未添加磷组（D1和D2）试验鱼的终末体质量、特定生长率和脊椎骨钙磷含量显著低于添加组(P<0.05),而饲料系数、全体和肌肉脂肪含量显著高于添加组(P<0.05)。当饲料中未添加磷时,添加0.5%钙对宝石鲈的特定生长率、饲料系数、全鱼和肌肉营养成分、脊椎骨的灰分和钙磷含量没有显著影响(P>0.05)。当饲料中添加0.6%磷时,钙的添加量（0~1.5%）对宝石鲈的终末体质量、特定生长率、饲料系数、全鱼组成、肌肉组成（水分、粗蛋白和灰分）和脊椎骨组成（粗灰分、磷和钙磷比）没有显著影响(P>0.05)。饲料中钙添加量过大（1.5%）组脊椎骨钙含量显著减少(P<0.05)。饲料中添加磷显著降低了鱼体中粗脂肪含量(P<0.05),但提高了脊椎骨钙磷的含量(P<0.05)。各组脊椎骨钙磷比均处于1.78～1.82范围内,组间差异不显著(P>0.05)。通过宝石鲈幼鱼生长性能和脊椎骨矿化作用分析表明,当饲料中添加0.6%磷时,钙的适宜添加量为0.5%。 关键词：宝石鲈;钙;磷     

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。     

Dietary lipid levels affect lipoprotein clearance,fatty acid transport,lipogenesis and lipolysis at the transcriptional level in muscle and adipose tissue of large yellow croaker (Larimichthys crocea)

To investigate the effect of dietary lipid levels on lipid metabolism in muscle and adipose tissue of large yellow croaker (Larimichthys crocea), fish (average body weight 150.0 g) were fed to one of three diets with a low (6%), moderate (12%, the control diet) or high (18%) crude lipid level for 10 weeks. The expression of genes related to lipoprotein clearance (lpl, ldlr, lrp1 and srbi), fatty acid transport (cd36, fatp1, fabp3 and fabp11), lipogenesis (fas and dgat2) and lipolysis (atgl, cpt1 and aco) in muscle and adipose tissue was analysed. In muscle of fish fed the low‐lipid diet, the expression of lpl, lrp1, fas, dgat2 and atgl was significantly downregulated, whereas fabp3 and fabp11 were significantly upregulated compared with those fed the control diet. In muscle of fish fed the high‐lipid diet, the expression of lpl, ldlr, lrp1, cd36, fabp3, fas and dgat2 was significantly decreased, while fabp11 expression was significantly increased compared with those fed the control diet. Compared with the control group, only a significant downregulation of fabp3 expression in adipose tissue was observed in the low‐lipid group. In the high‐lipid group compared with the control group, the expression of ldlr, fabp11, dgat2, atgl and aco in adipose tissue was significantly upregulated, whereas cpt1 expression in adipose tissue was significantly downregulated. These results indicated that the expression of the selected key genes related to lipid metabolism was tissue‐specific regulation by dietary lipid levels in large yellow croaker.     

Effects of different dietary lipid sources on growth performance,body composition and lipid metabolism‐related enzymes and genes of juvenile golden pompano,Trachinotus ovatus

Three groups of juvenile golden pompano, Trachinotus ovatus (54.75 ± 0.25 g), were each fed one of three diets containing different lipid sources: fish oil (FO), soybean oil (SO) and lard oil (LO). Fish were reared in sea cages for 8 weeks, and the fish fed the FO diet had significantly higher specific growth rate (SGR) but lower condition factor (CF) than the other treatments. The fatty acid (FA) composition of whole‐body lipids was closely correlated with those in the diets. Although no differences can be found in hepatic fatty acid synthase (fasn) activity, the carnitine palmitoyl transferase 1 (cpt1) activity in fish fed the FO diet was significantly higher compared with other treatments. In addition, the relative gene expression of lipid metabolism‐related enzymes, such as cpt1, fas, apolipoprotein B100 (apoB100), delta‐6 fatty acyl desaturase (fadsd6) and fatty acid‐binding protein 1 (fabp1), was also influenced by the different dietary lipid sources. Serum triglyceride (TG) and glucose content in fish fed the LO and FO diets were significantly higher than those in the SO group. Accordingly, it can be concluded that FO could not be completely replaced by SO or LO in golden pompano diets. The lipid sources of a diet could impose significant influence on body condition factor and hepatic lipid metabolism of golden pompano.     

Effects of dietary highly unsaturated fatty acid levels on growth,fatty acid profiles,antioxidant activities,mucus immune responses and hepatic lipid metabolism related gene expressions in loach (Misgurnus anguillicaudatus) juveniles

A 9‐week rearing trail was conducted to examine the effects of different dietary highly unsaturated fatty acid (HUFA) levels on the growth performance, fatty acid profiles, antioxidant activities, mucus immune responses and lipid metabolism‐related gene expressions of loach (Misgurnus anguillicaudatus) juveniles. Five test diets supplemented with 0%, 0.32%, 0.64%, 0.96% and 1.28% HUFA were used here. The loaches fed no HUFA diets had the lowest specific growth rate and survival rate. The loaches fed 0.32% HUFA diets had the lowest feed conversion rate and while no significant differences were found among the other four diet groups. Contents of hepatic eicosapentaenoic acid, docosahexaenoic acid and total polyunsaturated fatty acids were significantly increased with incremental dietary HUFA levels. Activities of hepatic superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT) in 0% HUFA group were lowest, while malondialdehyde was just the opposite. The lysozyme activity was significantly increased with incremental dietary HUFA levels. However, the activities of alkaline phosphatase and acid phosphatase reached a peak in 0.32% HUFA group. Loaches fed diets with HUFA significantly up‐regulated expressions of SOD, GPx, CAT and two lipid metabolism related genes. In conclusion, the optimal dietary HUFA level for loach juveniles was 0.64%–0.96%.     

不同水平亚麻籽油对罗非鱼肝功能和脂质代谢的影响

在基础饲料中分别添加0%、1.5%、3.0%、4.5%的亚麻籽油(LO)配制4种等氮(粗蛋白质33%)试验饲料,在淡水循环养殖系统中,分别饲喂初均重为(9.15±0.03)g的吉富罗非鱼(Oreochromis niloticus)8周,研究饲料中添加亚麻籽油对罗非鱼肝功能和脂质代谢的影响。结果显示:4.5%LO组鱼体肝胰脏脂肪和丙二醛(MDA)含量显著高于其他组,而各组间比肝重(HSI)无显著差异。随饲料中LO水平的增加,鱼体肝胰脏EPA、DHA、n-3 PUFA、n-3 HUFA含量及n-3/n-6比例显著升高,而3.0%LO水平后无显著变化。鱼体肝胰脏亚油酸和n-6多不饱和脂肪酸(n-6 PUFA)含量以对照组最高,4.5%LO组最低。各试验组鱼体肝胰脏中油酸、花生四烯酸(ARA)、饱和脂肪酸(SFA)和单不饱和脂肪酸(MUFA)含量无显著差异。随LO添加水平的增加,鱼体血液中胆固醇(CHOL)、甘油三酯(TG)及低密度脂蛋白胆固醇(LDL-C)含量也显著升高。而4.5%LO组血液中高密度脂蛋白胆固醇(HDL-C)含量显著低于其他组。4.5%LO组鱼体肝胰脏苹果酸脱氢酶(MDH)活性显著高于其他组,而脂蛋白脂酶(LPL)活性以1.5%和3.0%LO组最高。3.0%LO组鱼体肝胰脏超氧化歧化酶(SOD)和过氧化氢酶(CAT)活性显著高于其他组。而肝胰脏谷丙转氨酶(GPT)和谷草转氨酶(GOT)活性以4.5%LO组最低。结果表明,饲料中添加3.0%的亚麻籽油有利于罗非鱼肝胰脏和机体健康。     

饲料脂肪含量与奥尼罗非鱼幼鱼肝脏形态结构特征的相关性

研究了投喂不同脂肪含量饲料时奥尼罗非鱼幼鱼（Oreochromis niloticus×O．aureus）肝脏形态学与组织学的变化规律，旨在阐明饲料脂肪对奥尼罗非鱼幼鱼脂肪肝发生的影响。饲料脂肪水平设置为0％、2％、4％、6％和8％等5个梯度组。随着饲料脂肪水平逐渐升高，奥尼罗非鱼幼鱼的增重率与肥满度均先上升后下降，1～5组肥满度分别为1．63±0．14、1．78±0．21、1．92±0．18、1．80±0．21和1．74±0．24。脂肪水平对奥尼罗非鱼肝脏形态学有明显影响，4～5组病鱼的肝胰脏肿大，呈油腻状，颜色发黄，柔软粉糊，有的出现白色坏死病灶，部分胆囊肿大且颜色变深，肠系膜均有过量的白色脂肪沉积。脂肪水平对奥尼罗非鱼肝脏组织学亦有明显影响，1～5组试验鱼的肝细胞直径随之增大，低脂肪水平的1～3组与高脂肪水平的4～5组具有显著差异，平均值分别为8．9和17．9μm，高脂肪水平的4～5组呈现肝细胞核偏位、胞浆内脂肪滴较多、细胞透明空泡化等症状。研究认为奥尼罗非鱼幼鱼饲料中脂肪添加量超过4％时对其肝脏形态学与组织学有一定影响。     

Preliminary study to evaluate the effects of dietary bile acids on growth performance and lipid metabolism of juvenile genetically improved farmed tilapia (Oreochromis niloticus) fed plant ingredient‐based diets

A 9‐week feeding experiment was conducted to investigate the effects of dietary bile acids (BAs) on juvenile genetically improved farmed tilapia (GIFT) (Oreochromis niloticus) based on the evaluations of growth performance and parameters relevant to lipid metabolism. Each of five vegetable protein‐based diets containing BAs at a level of 0, 0.05, 0.15, 0.45 or 1.35 g/kg diet was fed to three replicates with 40 fish (8.2 g per fish). The results showed that weight gain (WG) increased significantly with the increase in BAs from 0 to 0.15 g/kg diet and then decreased significantly at a higher BA supplementation. Dietary BAs significantly reduced the crude lipid content in the whole body, muscle and liver tissue of GIFT. Fish fed diet with 1.35 g BAs/kg diet developed serious nuclear migration and vacuolization in hepatocytes. Gall bladder appeared to contain white solid and has fragile capsules. Dietary BA supplementation had significant effects on serum biochemical indices and activities of lipid metabolism enzymes in liver and intestine. In conclusion, dietary bile acid supplementation (0.15 g/kg) can facilitate the lipid metabolism and therefore promote the growth of tilapia. However, overdosed dietary BAs induced gallstone development, disrupted lipid metabolism and depressed the growth performances of GIFT.     

Effects of dietary palm oil source on growth,tissue fatty acid composition and nutrient digestibility of red hybrid tilapia,Oreochromis sp., raised from stocking to marketable size

A 20-week feeding trial was carried out to investigate the influence of three palm oil products as the principal dietary lipid source on the growth performance, proximate composition, tissue fatty acid composition and nutrient digestibility of red hybrid tilapia (Oreochromis sp.) fed these diets from stocking to marketable size. Four isonitrogenous (30% crude protein) and isoenergetic (16.5 kJ g^− 1) practical diets were formulated with 8% of added fish oil (FO), crude palm oil (CPO), palm fatty acid distillate (PFAD) or refined, bleached and deodorized palm olein (RBDPO), respectively. Each diet was fed to triplicate groups of 30 fish of 31.24 ± 0.05 g mean initial body weight. The tilapia were raised at 29 ± 1 °C in 12 round 1000 L fiberglass tanks with a continuous water flow rate of about 1.8 L/min.Results showed that the source of added lipid did not significantly influence (P > 0.05) final body weight, specific growth rate, feed conversion ratio, survival, body indices, hematocrit and production yield of tilapia. There was no significant difference in the fillet proximate composition of fish fed the various diets, except that fish fed the PFAD diet showed lower lipid deposition. The deposition of fatty acids in fish tissues was generally influenced by the fatty acid profile of the diets. Fillet fatty acid profiles of tilapia fed palm oil-based diets had significantly higher concentrations of saturated and monounsaturated fatty acids, but lower levels of polyunsaturated fatty acids (PUFA) compared to the fish fed the FO diet. Fillet of fish fed the FO diet had significantly higher concentrations of EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) compared with fish fed palm oil-based diets. Dietary lipid source did not significantly affect dry matter and protein digestibility (62.1–64.8% and 83.5–85.0%, respectively). The inclusion of dietary palm-origin oils significantly reduced the total lipid digestibility of the diets due mainly to the decreased digestibility of the saturated fatty acids. In all treatments, the apparent digestibilities of both n − 3 and n − 6 PUFA were the highest, followed by monoenes, while the lowest were the saturated fatty acids. Despite the high free fatty acid content of PFAD (92.2%) compared to CPO (4.8%) and RBDPO (0.1%), the different free fatty acid content did not significantly affect the nutrient digestibility of the palm oil-based diets. Results obtained confirmed the feasibility of feeding tilapia with palm oil-based diets with a 100% substitution of added dietary fish oil throughout the grow-out cycle until marketable size.