投喂频率对池塘循环水养殖大口黑鲈消化酶、组织结构及脂代谢酶基因表达的影响

为研究池塘工程化循环水养殖模式下投喂频率(2 次/d、3 次/d、4 次/d)对大口黑鲈(Micropterus salmoides)体成分、肠道消化和肝脏组织结构及脂蛋白酯酶(LPL)和肝脂酶(HL)基因相对表达丰度的影响, 选用平均体重为 (5.0±0.4) g 的大口黑鲈为研究对象, 在池塘工程循环水养殖系统中进行为期 120 d 的养殖实验。结果表明, 投喂频率对鱼体全鱼的粗脂肪和灰分含量影响显著(P<0.05); 投喂频率 2 次/d 组的灰分含量显著高于其他两组, 而 2 次/d 组体脂肪含量低于投喂 3 次/d、4 次/d 组, 体水分和粗蛋白含量均不受投喂频率的影响(P>0.05); 投喂频率 2 次/d 组肠道淀粉酶和脂肪酶活性显著高于 4 次/d 投喂组(P<0.05); 投喂频率对大口黑鲈肠道绒毛高度和宽度影响不显著 (P>0.05), 4 次/d 组肠道绒毛排列整齐度下降且肌层厚度显著低于 2 次/d 和 3 次/d 组(P<0.05)。肝脏组织学显示, 投喂频率越高肝脏脂肪堆积加重, 相对于 2 次/d 和 3 次/d 组, 4 次/d 组肝细胞偏移、空泡化的现象较明显。在第 60 天和 90 天, 2 次/d 组 LPL 基因相对表达量显著高于 4 次/d 组(P<0.05); 而在第 120 天时, LPL 的相对表达量在各组间差异不显著(P>0.05)。2 次/d 组 HL 基因相对表达量显著高于 4 次/d 组(P<0.05)。综合分析, 在饱饲投喂条件下, 池塘循环水养殖大口黑鲈的适宜投喂频率为 2 次/d。     

禁食对大口黑鲈生长和肝脏IGF-I mRNA表达丰度的影响

运用实时荧光定量PCR技术,研究禁食对体质量为(100+1)g的1龄大口黑鲈(Micropterus salmoides)的生长和肝脏中类胰岛素生长因子-I(IGF-I)mRNA表达丰度的影响.在为期6周的实验期间,对照组每天表观饱食投喂2次;禁食组禁食3周后恢复投喂3周.实验期间对照组鱼体质量和体长逐渐增加.6周后,对照组鱼体增重率为10.99%,体长增加率为3.07%.禁食组禁食3周期间,鱼体质量下降了5.08%、体长减少了1.79%.同时肝组织IGF-I mRNA表达水平呈下降趋势,禁食结束时仪为对照组的29.93%.恢复投喂2周后肝组织IGF-I mRNA的表达量仍显著低于对照组(P＜0.05),鱼体质量为实验初始水平的98.54%,体长为实验初始水平的99.03%;恢复投喂3周后,禁食组鱼体质量、体长恢复到实验初始时水平(P＞0.05),但仍与对照组有显著差异(P＜0.01);肝组织IGF-I mRNA的表达丰度与对照组无显著性差异(P＞0.05).结果显示,禁食使大口黑鲈体质量、体长下降,同时肝组织IGF-I mRNA表达丰度也随之降低;而恢复投饲后,其生长、肝脏IGF-I mRNA的表达丰度也逐渐恢复.研究表明,鱼类的营养状况、生长和与IGF-I mRNA的表达之间存有正相关关系.     

投喂频率对史氏鲟幼鱼生长、抗氧化和免疫指标的影响

为探究史氏鲟(Acipenser schrenckii)幼鱼的最低适宜投喂频率,将实验鱼的投喂频率分别设定为2、1、0.5、0.25、0.125次/d,养殖56 d后测定其生长、抗氧化和免疫指标。结果显示,随着投喂频率降低,史氏鲟幼鱼的增重率、特定生长率、肝体比和脏体比显著降低(P0.05),但存活率和肥满度无显著性变化(P0.05)。在抗氧化指标中,随着投喂频率降低,肝脏T-AOC、SOD活性呈逐渐降低的趋势,2次/d组T-AOC活性与0.5、0.25、0.125次/d组均存在显著差异(P0.05),但各组之间SOD活性差异不显著(P0.05);肝脏CAT活性和GSH含量呈先升高、后降低的趋势,0.5、0.25次/d组肝脏CAT活性显著高于0.125次/d组(P0.05),1次/d组GSH含量显著高于0.5、0.25和0.125次/d组(P0.05);肝脏MDA含量呈逐渐增加的趋势,0.5、0.25、0.125次/d组MDA含量显著高于2、1次/d组(P0.05)。免疫指标中,随着投喂频率降低,实验鱼肝脏LZM活性逐渐降低,2次/d组与0.125次/组差异显著(P0.05);而肝脏IgM含量呈先升高、后降低的趋势,0.25次/d组显著高于2、0.125次/d组(P0.05)。综合各项指标,建议史氏鲟幼鱼的最低适宜投喂频率为1次/d,以避免投喂频率过低对鱼体造成的胁迫氧化损伤。     

周期性“饥饿-再投喂”对大口黑鲈幼鱼补偿生长的影响

在水温(26.5±1.2)℃下,将体质量(45.70±0.56)g的大口黑鲈Micropterus salmoides幼鱼分为4组,饲养在采光大棚内的30m~2水泥池中,每池40尾,D0组每天饱食投喂2次,D1、D2、D3组分别投喂6d、5d、4d,饥饿1d、2d、3d,持续8周,每组3个重复池塘,研究周期性"饥饿-再投喂"对大口黑鲈幼鱼补偿生长的影响。结果发现,随着每周饥饿天数的增加,大口黑鲈的末体质量和增重率均不同程度下降,但D1组与D0组无显著差异(P0.05)。大口黑鲈的日摄食量随饥饿时间的增加而显著提高(P0.05),但各组间无显著差异(P0.05)。D1组的饲料利用效率和蛋白质效率与D0组无显著差异(P0.05);而D2和D3组显著低于D0组(P0.05)。试验结束时,鱼体粗蛋白和粗脂肪含量随饥饿时间增加而下降。D3组鱼的胃和肠道蛋白酶活性显著低于D0组(P0.05);D1组的胃和肠道脂肪酶活性较高;D1和D2组胃淀粉酶活性较高,肠道淀粉酶活性则随着饥饿时间增加显著上升(P0.05)。饥饿使大口黑鲈血清甘油三酯和总胆固醇含量降低,血清谷草转氨酶和谷丙转氨酶活性增加。血清生长激素水平随着饥饿时间增加而上升,类胰岛素生长因子-Ⅰ水平则下降(P0.05)。结果表明:每周投喂6d饥饿1d的大口黑鲈饲料转化效率较高,实现了完全补偿生长,可供集约化养殖的科学投喂参考。     

配合饲料和冰鲜鲢对大口黑鲈生长、血浆生化指标、抗氧化能力和组织学的影响

为探讨不同来源饲料对大口黑鲈生长、血浆生化指标、抗氧化能力以及肝脏和肠道组织学的影响,实验选取初始体质量为(12.45±0.07)g的大口黑鲈180尾,随机分成2个处理,每个处理3个重复,每个重复30尾,分别投喂配合饲料和冰鲜鲢,养殖84 d。结果显示,配合饲料组大口黑鲈的增重率(WGR)、特定生长率(SGR)和饲料系数(FCR)显著低于冰鲜鲢组,而蛋白质效率(PER)、肝体比(HSI)和脏体比(VSI)显著高于冰鲜鲢组。大口黑鲈摄食配合饲料后,肝糖原含量显著高于冰鲜鲢组,肝脏蛋白酶活性显著低于冰鲜鲢组,而肌糖原和肠淀粉酶活性无显著差异。饲喂配合饲料组大口黑鲈血浆谷草转氨酶(AST)活性、血糖和丙二醛(MDA)含量以及Ca/P比值显著高于冰鲜鲢组,而血浆碱性磷酸酶(ALP)、超氧化物歧化酶(SOD)和谷胱甘肽过氧化物酶(GSH-Px)活性以及总蛋白(TP)、甘油三酯(TG)、尿素、钙和磷含量显著低于冰鲜鲢组。各实验组血浆谷丙转氨酶(ALT)活性以及胆固醇(TC)和胰岛素含量均无显著差异。配合饲料明显影响大口黑鲈肝脏和肠道的组织结构,饲喂配合饲料组实验鱼的肝脏空泡化现象严重,小肠绒毛受到严重机械性损伤。研究表明,在本实验条件下,冰鲜鲢更适合饲喂大口黑鲈,配合饲料不仅影响大口黑鲈的生长,而且损伤肝脏和肠道的健康。因此,可以借鉴冰鲜鲢的营养组成和大口黑鲈的代谢特性,深入研发大口黑鲈的饲料配制技术。     

不同投喂频率对脊尾白虾生物钟基因表达、生长及肌肉成分组成的影响

为探究不同投喂频率对脊尾白虾(Exopalaemon carinicauda)生长的影响, 确定脊尾白虾养殖适宜投喂频率, 本研究分析了在不同投喂频率下脊尾白虾眼柄和肝脏中的生物钟基因表达节律变化, 评估了不同投喂频率对脊尾白虾生物钟系统同步性的影响, 并开展了生长及肌肉组成的同步养殖验证。结果表明: 在投喂频率为＜3 次/d 时, 生物钟基因的表达节律并没有随着投喂频率的改变而发生变化, 无论在眼柄或肝脏中均表现出相似的表达周期及表达顶相, 且各自的表达量间也无显著性差异变化。然而, 当投喂频率增加到 4 次/d 时, 肝脏中部分生物钟基因的表达节律发生了显著变化, 表现为表达周期改变、相位明显偏移及表达量变化。其中, 投喂频率为 3 次/d 时, 脊尾白虾眼柄与肝脏中生物钟基因表达节律的同步性最高。生长结果也显示, 脊尾白虾的生长性能随投喂频率升高(从 1 次/d 至 3 次/d 时)而升高, 3 次/d 时达到最高, 其特定生长率及增重率分别为(6.65±0.98)%/d 和(199.46±5.42)%。同时, 随着投喂频率升高, 脊尾白虾肌肉组织中的粗蛋白及粗脂肪含量也呈现上升趋势, 在 3 次/d 时达到最高, 分别为(19.98±0.04)%和(1.88±0.23)%。投喂频率对脊尾白虾肝脏中生物钟基因的表达节律有重要影响, 表明该因素对重置或调控脊尾白虾外周生物钟系统有一定的牵引作用。     

大口黑鲈配合饲料中3种动物蛋白源的不同添加比例对其生长性能、肠道健康及蛋白质代谢的影响

目前,大口黑鲈(Micropterus salmoides)配合饲料对鱼粉的依赖性大,而鱼粉价格不断上涨,导致其饲料成本居高不下,严重制约了其养殖业的健康发展。为降低饲料成本,本研究以鱼粉、鸡肉粉和猪肉粉为饲料动物蛋白源,制作7种配合饲料(D1~D7),其鱼粉/鸡肉粉/猪肉粉的添加百分比分别为45.0/22.6/0、37.1/22.6/8.0、28.8/22.6/16.0、45.0/14.5/8.0、45.0/5.3/16.0、41.6/18.0/8.0和37.0/13.8/16.0。采用上述饲料投喂大口黑鲈幼鱼(初始体重约为55 g) 60 d,评估饲料动物蛋白源组合对鱼生长性能、组织生化指标、肌肉质构特性以及肝脏蛋白质代谢和肠道炎性因子相关基因表达的影响。结果显示,相比于其他饲料投喂组,D3组鱼的终末体重、增重率、特定生长率显著提高,饲料系数显著降低(P<0.05);D3组全鱼粗蛋白质显著高于D5组,其粗脂肪水平显著低于D4和D6组(P<0.05)。在组织生理生化指标方面,D3组鱼血清总氨基酸含量显著高于D1和D4组(P<0.05),而其谷草转氨酶活性显著低于D5组(P<0.05);D3组鱼肝脏总蛋白含量显著高于D7组(P<0.05)。在肌肉品质方面,D3组肌肉硬度和胶着性以及咀嚼性分别显著低于D4组和D6组(P<0.05)。此外,D3组肠抗炎基因il-10,肝脏蛋白质合成基因tor、s6k1、akt、pi3k mRNA表达水平上调,显著高于D7组(P<0.05);而肠促炎因子il-1β、il-6和肝脏翻译抑制因子4ebp-1 mRNA表达水平下调,显著低于D1组(P<0.05)。上述结果表明,饲料中添加28.8%鱼粉、16.0%猪肉粉和22.6%鸡肉粉对大口黑鲈的促生长效果最优,且有利于提高肝脏蛋白质合成,维护肠道健康。研究结果可为降低大口黑鲈配合饲料对鱼粉的依赖提供技术支撑。     

17α-甲基睾酮对大口黑鲈生长及性腺发育的影响

为探索建立大口黑鲈(Micropterus salmoides)生理雄鱼诱导技术, 以出膜后 15 d 体长(15.1±0.09) mm 的大口黑鲈为研究对象, 分别使用含有 17α-甲基睾酮(MT)的日粮饲喂 60 d。饲料 MT 添加量分别为 0 mg/kg (MT0)、 50 mg/kg (MT50)和 100 mg/kg (MT100), 分析其对大口黑鲈生长、性别分化、性类固醇激素含量及性腺发育相关基因表达水平的影响。结果表明, MT50 和 MT100 组大口黑鲈的体长和体重均显著低于 MT0 组(P＜0.05), MT50 和 MT100 组的雄性率均为 100%, 显著高于 MT0 组(45%); 性腺组织切片显示, MT 诱导获得的生理雄鱼性腺结构与 MT0 组雄鱼相似。性类固醇激素测定结果显示, MT50 和 MT100 组生理雄鱼血清中雌二醇的含量均显著低于 MT0 组雌鱼(P＜0.05), MT50 组生理雄鱼睾酮的含量显著高于 MT100 组(P＜0.05), 与 MT0 组雌鱼无显著差异(P＜0.05)。 此外, 与 MT0 组雌鱼相比, MT50 和 MT100 组生理雄鱼性腺中 Dmrt1 和 Gsdf 基因的表达水平显著上调(P＜0.05), 而 Foxl2 和 Cyp19a1a 基因的表达水平显著下调(P＜0.05)。研究结果表明, MT 添加投喂能有效诱导出膜后 15 d 的雌性大口黑鲈转为生理雄性个体, 适宜添加量为 50~100 mg/kg。本研究为大口黑鲈全雌品种培育奠定了基础。     

投喂频率对绿鳍马面鲀幼鱼生长、生理指标及肝脏hsp70基因表达丰度的影响

为探究投喂频率对绿鳍马面鲀(Tharnnaconus septentrionalis)幼鱼生长、生理指标及肝脏hsp70基因表达的影响,本研究设5个投喂频率,分别为1、2、3、4和5次/d (分别简称为F1、F2、F3、F4和F5),每个处理组设3个平行,每缸养殖30尾鱼[(6.47±0.56)g]。实验期间,水温为17℃~26℃,盐度为30~31,pH为6.8~7.6,溶解氧≥5 mg/L,养殖周期为30 d。结果表明,不同投喂频率对绿鳍马面鲀幼鱼的生长、体成分、消化酶和抗氧化酶活性均有影响。随着投喂频率的增加,绿鳍马面鲀幼鱼的摄食和生长均呈上升趋势,F5组数值最大,摄食率为3.95%,增重率为347.19%,特定生长率为5.07%/d,增重率为F1组的2倍多。F1组的肥满度为1.79,显著低于其他4组(P<0.05);肝体比逐渐升高,F4和F5组的肝体比显著高于其他3组(P<0.05)。增加投喂频率,鱼体的粗蛋白含量呈先升高后降低的趋势,F2组最高,为59.82%;粗脂肪含量呈逐渐升高的趋势,F5组最高,为31.23%。胰蛋白酶活性随投喂频率增加呈先降低后增加的趋势,F3组活性最低,为37.48 U/μg prot;脂肪酶活性逐渐升高,F5组最高,为2.67 U/g prot;淀粉酶活性不受投喂频率的影响(P>0.05)。过氧化氢酶、超氧化物歧化酶活性和丙二醛含量最高均在F5组,分别为14.71 U/mg prot、250.32 U/mg prot和2.73 nmol/mg。肝脏中hsp70基因的相对表达量不受投喂频率的影响(P>0.05)。基于绿鳍马面鲀幼鱼的生长性能和生理效应的综合考虑,其最适投喂频率为3次/d。     

人工饲养条件下额外投喂海蜇对银鲳生长及代谢酶活性的影响

以银鲳(Pampus argenteus)为研究对象,进行了5组不同频率额外投喂海蜇(Rhopilema esculentum)的实验,依次为无额外投喂海蜇组(对照组)、1次/d、1次/3 d、1次/6 d和1次/12 d(依次标记为O组、A组、B组、C组和D组),通过分析实验中期(36 d)和实验结束时(60 d)银鲳的生长情况及其不同组织中主要蛋白与脂类代谢相关酶活性的变化,揭示银鲳在额外投喂海蜇过程中,其生长、机体蛋白和脂类代谢指标的变化。结果显示,36 d和60 d时,高频率额外投喂海蜇组(A组和B组)银鲳增重率和特定生长率显著高于D组,但与对照组无显著差异(P0.05);各组血清和肝脏中谷丙转氨酶(GPT)和谷草转氨酶(GOT)活性均无显著差异(P0.05);60 d时,A组血清脂蛋白酯酶(LPL)活性显著高于其它各组,各组间肝脏与肌肉中LPL活性无显著性差异;60 d时,高频率组(A组和B组)肝脏脂肪酸合成酶(FAS)活性显著高于低投喂频率组(C组和D组)(P0.05),肌肉组织中,额外投喂海蜇试验组FAS活性均显著高于对照组。结果表明,高频率投喂海蜇可提高银鲳组织代谢酶的活性,特别是脂代谢相关酶的活性,从而促进机体对营养物质的消化吸收,在一定程度上提高银鲳的生长率,在银鲳人工养殖过程中,基于机体代谢指标的分析,每3天额外投喂一次海蜇较为适宜。     

Effects of different feeding frequency on the growth, survival and feed conversion ratio of the Asian sea bass Lates calcarifer juveniles reared under hypersaline seawater of the Red Sea

The effects of several feeding frequencies of two, three and four times per day on Asian sea bass Lates calcarifer growth performance have been tested. Fish were reared under ambient Red Sea water conditions; these fish were fed diets containing 48% crude protein for 45 days. The present study was carried out at the Faculty of Marine Science (Abhor branch). The results show that fish population fed twice daily had significantly better growth with a mean body weight and daily weight increment of 59.04 and 1.31 g, respectively (P<0.05), than the other population fed three or four times daily. No significant differences were observed between fish fed two and three times daily in length gain and daily length increment. Growth in weight and length was increased gradually and no mortality was observed during the experimental period. In all the feeding trials, the body weight increased with an increase in length (R²=0.87 and 0.90). The feed conversion ratio (FCR) was significantly affected by feeding frequencies, with a significantly better FCR value of 2.43 in fish fed twice daily (P<0.05) compared with the other two populations fed three and four times daily. These results led to the conclusion that feeding two times daily would result in better growth and utilization of feed for the Asian sea bass L. calcarifer juvenile.     

饥饿及再投喂处理对草鱼生长、葡萄糖代谢和转运蛋白1表达的影响

设置持续投喂组(C,持续投喂8周)、饥饿再投喂组(R,饥饿4周+再投喂4周)和持续饥饿组(S,饥饿8周)3个处理组,研究3种不同饥饿处理对草鱼(Ctenopharyngodon idellus)血清生化指标、糖原和糖代谢相关酶和葡萄糖转运蛋白1(GLUT1)的影响,同时在此实验基础上研究草鱼在急性高糖负荷胁迫下的糖耐受能力、糖代谢相关酶和GLUT1的变化规律,旨在阐明草鱼在饥饿及再投喂处理条件下的糖代谢特征。选取初重为(125.35±0.54)g的草鱼,饲养8周后以30 mg/100 g体重的剂量腹腔注射葡萄糖研究其糖耐受能力。结果显示,S组肝糖原和血清的血糖、甘油三酯含量均最低。饥饿处理对草鱼糖耐受能力影响显著,S组血糖含量在各时间点上显著低于其余两组(P0.05),肝糖原在6 h达到峰值;饥饿处理对草鱼肝脏糖代谢关键酶影响显著,饥饿处理(S组)诱使磷酸烯醇式丙酮酸激酶(PEPCK)活性上升但抑制丙酮酸激酶(PK)和果糖-6-磷酸激酶(PFK)的活性(P0.05),而饥饿再投喂(R组)后PEPCK、PK和PFK酶活性恢复到持续投喂(C组)处理水平。注射葡萄糖后S组肝脏GK酶活性增幅最大,PK酶活性呈上升趋势,而R组则呈先下降后上升的趋势;饥饿处理对草鱼肝脏和肌肉GLUT1表达影响显著,注射葡萄糖后,除R组肝脏组织外,其余各组草鱼肝脏和肌肉组织GLUT1表达量均呈先上升后下降的趋势,且S组肌肉GLUT1表达量在各个时间点上均高于其余两组(P0.05)。研究结果表明,在不同饥饿处理下,草鱼可通过消耗肝糖原和甘油三酯及降低肝脏糖酵解相关酶(PK和PFK)活性和促进糖异生PEPCK酶活性来应对饥饿胁迫,而饥饿处理可诱使GK和PK酶活性上升、促进糖原合成和激活GLUT1基因的表达和转运来缓解草鱼急性高糖负荷,从而提高其糖耐受能力。     

不同饲料料型及投喂频率对斑点叉尾鮰幼鱼生长及肌肉品质的影响

本研究旨在探究不同饲料料型及投喂频率对斑点叉尾鮰(Ictalurus punctatus)生长及肌肉品质的影响。研究采用双因素试验设计,以饲料料型(膨化饲料,EF;颗粒饲料,PF)和投喂频率(2次/日,F2;3次/日,F3)为影响因素,共4个组,分别命名为EFF2、PFF2、EFF3和PFF3,每组3个平行,投喂8周,每天定时投喂两次(7:30和16:30)或3次(7:30, 12:00, 16:30)。结果显示,斑点叉尾鮰的末重和增重率受到投喂频率的影响,F2组显著高于F3组(P0.05);而饲料料型则对斑点叉尾鮰的生长无显著影响(P0.05)。颗粒饲料组的肌肉粗脂肪含量和内聚性、回复性显著低于膨化饲料组(P0.05),而硬度显著高于膨化饲料组(P0.05)。F3组的肌肉硬度、胶着性和咀嚼性则显著高于F2组(P0.05)。颗粒饲料组生肌调节因子5 (myogenic factor 5, Myf5)和肌肉生长抑制素(myostatin,MSTN)基因的相对表达量显著低于膨化饲料组(P0.05)。F3组肌肉中MSTN基因相对表达量显著高于F2组,而肌细胞生成素(myogenin,MyoG)基因相对表达量则呈现相反趋势。综上,投喂同种配方的膨化饲料和颗粒饲料对斑点叉尾鮰的生长效果相似,但是投喂颗粒饲料的斑点叉尾鮰硬度更大,而投喂膨化饲料则肌肉脂肪含量更高;斑点叉尾鮰的最佳投喂频率是每天2次。     

饲料中添加姜黄素对尼罗罗非鱼幼鱼生长和四氯化碳诱导肝损伤的影响

本试验旨在研究饲料中姜黄素对尼罗罗非鱼(Oreochromis niloticus)幼鱼生长性能的影响和对四氯化碳(CCl_4)诱导鱼体急性肝损伤的保护作用,为筛选治疗鱼类肝脏综合征的绿色药物提供理论依据。在基础饲料中分别添加不同水平(0、15 mg/kg、30 mg/kg、60 mg/kg、120 mg/kg和240 mg/kg)的姜黄素,连续饲喂鱼体8周后进行采样,探讨姜黄素对尼罗罗非鱼生长的影响,并采用CCl_4诱导鱼体急性肝损伤,72 h后采集血液和肝组织,检测相关抗氧化指标以及肝组织切片的变化。结果显示,饲料中添加60 mg/kg和120 mg/kg姜黄素可显著增加鱼体的增重率和特定生长率(P0.05);当罗非鱼经CCl_4诱导72 h后,60 mg/kg和120 mg/kg姜黄素组的血浆谷草转氨酶(GOT)、谷丙转氨酶(GPT)活力和丙二醛(MDA)含量显著低于对照组(P0.05),而血浆总蛋白(TP)、白蛋白(ALB)、谷胱甘肽(GSH)、血浆总抗氧化能力(T-AOC)、肝超氧化物歧化酶(SOD)活力、谷胱甘肽过氧化物酶(GSH-Px)活力却显著高于对照组(P0.05);姜黄素在一定程度上可保护鱼体肝不受损伤,且以添加120 mg/kg水平时效果最佳。综上,饲料中添加60～120 mg/kg姜黄素可促进尼罗罗非鱼幼鱼生长性能的提高,而当饲料中添加120 mg/kg姜黄素时,对其肝的保护作用最强,可有效地抑制肝组织的脂质过氧化。     

Effects of feeding frequency on growth,feed efficiency and body composition of juveniles Brazilian sardine,Sardinella brasiliensis (Steindacher 1879)

The Brazilian sardine is the most important fishery resource in Brazil. Their production has declined along the last 30 years due the overfishing, climatic and oceanographic phenomena. This study was carried out to determine the optimal feeding frequency for juvenile Brazilian sardine based on growth, feed efficiency, feed intake and body composition. Six feeding frequencies of one, two, three, four, five and six times a day were evaluated in triplicate tanks for 50 days. Fish with initial mean weight of 3.29 ± 0.56 g were fed daily to apparent satiation. The results showed that fish fed once daily had lower body weight gain, specific growth rate and condition factor (P < 0.05) compared with other treatments. The feed efficiency ratio in fish fed once daily was significantly higher (P < 0.05) than those fed two or more times a day. No significant differences were observed in the coefficient of variation in body weight (P > 0.05) among the treatments. Feed intake was directly proportional to the feeding frequency. Fish fed once daily showed lower hepatosomatic and mesenteric fat indices (P < 0.05) than the other treatments. Neither protein nor ash content of fish were significantly (P > 0.05) affected by feeding frequency. However, the lipid content increased with feeding frequency. The results suggest that the optimal feeding frequency for juvenile Brazilian sardine is at least twice daily.     

Effect of Feeding Frequency on Sex-Reversal and on Growth on Nile Tilipia,Oreochromis niloticus

Methyltestosterone-treated feed was fed at four different feeding frequencies to Oreochromis niloticus fry held in hapas in order to evaluate the effect on sex reversal and on growth. Sex reversal rates greater than 97% were obtained for feeding rates ranging from 2 times/day, 5 days/week, to 4 times/day, 7 days/week. Greatest growth and lowest feed conversion occured when the fry were fed 4 times/day vs. 2 times/day. Fish were graded to sizes &#le; 15 mm and > 15 mm at the end of the 30-day treatment period and later sexed. There was no difference in the percent males between small or large fish.     

Evaluation of mixed feeding schedules with respect to compensatory growth and body composition in African catfish Clarias gariepinus

An 8‐week feeding trial was conducted in a recycling water system at 28 ± 1 °C to investigate compensatory growth and body composition in African catfish Clarias gariepinus (13.05 ± 0.05 g). A fishmeal‐based diet containing 350 g kg^?1 protein and 17.5 kJ g^?1 gross energy was fed to triplicate groups of 20 fish (per 30‐L tank). Fish were fed the diet either to satiation or feed restricted in six feeding schedules as satiation 56 days; restricted 28 days + satiation 28 days; restricted 14 days + satiation 14 days; restricted 7 days +satiation 7 days; restricted 3 days + satiation 4 days; and restricted 2 days + satiation 2 days. The restricted regime was achieved by offering fish 1% (maintenance ration) of their body weight per day adjusted after fortnightly weighing. African catfish showed partial compensatory growth under alternating periods of feed restriction and satiation feeding with significantly different values (P < 0.05) from fish fed in satiation throughout. However, significantly indifferent (P > 0.05) values of feed, protein, lipid and energy utilization were found under alternating periods of feed restriction and satiation feeding. Significantly higher (P < 0.05) feed intake was observed in treatment with satiation throughout than those in other treatments. All the feeding schedules showed no significant differences (P > 0.05) on body composition, organ indices, eviscerated carcass composition, viscera lipid and liver lipid. These studies reveals that C. gariepinus showed partial compensatory growth responses at alternating periods of restricted and satiation feeding.     

投喂频率对斑点叉尾鮰幼鱼生长、饲料利用和鱼体组成的影响

通过8周的生长试验,研究斑点叉尾鮰(Ictalurus punctatus)幼鱼(初始体重约4.5 g)的最适投喂频率。试验饲料为自制配合饲料,粗蛋白38%,总能19.0 kJ/g。设计了1～5次/d(M1-M5)5种投喂频率。结果表明:M2、M3、M4组摄食率均显著高于M1和M5组(P<0.05),其中M4组最大。M3、M4、M5组的特定生长率均显著高于M1组(P<0.05),其中M3组最大。M2、M3、M4、M5组的干物质表观消化率均显著高于M1组(P<0.05),M3和M4组的蛋白和能量表观消化率均显著高于M1和M2组(P<0.05)。M3组干物质含量显著高于M1和M2组(P<0.05),M2、M3、M4和M5组的粗蛋白、粗脂肪和能量含量均显著高于M1组(P<0.05)。因此,本研究建议,斑点叉尾鮰幼鱼养殖的最适投喂频率为3次/d。     

High dietary starch impaired growth performance,liver histology and hepatic glucose metabolism of juvenile largemouth bass,Micropterus salmoides

A 60‐day experiment was carried out to investigate dietary starch levels on growth performance, hepatic glucose metabolism and liver histology of largemouth bass, Micropterus salmoides. Fish (initial weight 22.00 ± 0.02 g) were fed five graded levels of dietary corn starch (0, 50, 100, 150 and 200 g/kg). Fish fed low (0 and 50 g/kg) dietary starch showed significantly higher weight gain than other groups (p < .05). Liver lipid and glycogen accumulations were induced when dietary starch higher than 100 g/kg. After 20 days of feeding, hexokinase activity and mRNA expression were decreased in fish fed dietary starch higher than 150 g/kg (p < .05) and the pyruvate kinase showed the opposite tendency. Insulin receptor 1 (irs1), glucagon‐like peptide‐1 receptor and glucose transport protein 2 (glut2) mRNA expression were decreased with the increasing dietary starch after 10 days of feeding (p < .05). These results indicated gluconeogenesis was depressed and β‐oxidation was enhanced in response to high dietary starch, while the glycolysis was inhibited and endocrine system was impaired when fish fed high dietary starch; then, glucose homeostasis was disturbed and finally led to the glucose intolerance of largemouth bass.