高糖饲料对吉富罗非鱼生长性能、饲料利用和糖脂代谢的影响

为探讨高糖饲料对吉富罗非鱼(GIFT Oreochromis niloticus)生长性能、饲料利用和糖脂代谢的影响,设置糖水平为34%的对照饲料(C组,能量水平13.68 k J·g-1)、糖水平为48%的高糖高能饲料(HCE组,能量水平16.03 k J·g-1)和高糖等能饲料(HE组,能量水平13.81 k J·g-1),在室内循环水系统中饲养初始体质量(20.34±0.42)g的吉富罗非鱼幼鱼60 d。结果表明,HCE组和HE组的增重率、特定生长率、肝脏粗蛋白均显著低于C组(P0.05),饲料系数、肝脏粗脂肪、肝糖原、总糖表观消化率、血清低密度脂蛋白胆固醇和高密度脂蛋白胆固醇均显著高于C组(P0.05);HE组增重率、全鱼粗脂肪、血清甘油三酯和总胆固醇均显著低于HCE组(P0.05);高糖组肝脏葡萄糖激酶显著高于C组,HE组葡萄糖-6-磷酸脱氢酶、苹果酸酶、脂肪酸合成酶活性最高,C组最低(P0.05);由肝脏组织切片看出,高糖饲料引起吉富罗非鱼肝脏细胞肿大变形,出现空泡,HCE组对肝脏损伤更加显著。研究结果表明,吉富罗非鱼能够耐受48%糖水平的饲料,但长期摄食导致鱼体糖脂代谢紊乱,尤其影响脂肪代谢,造成鱼体脂肪蓄积,肝功能损伤,不利于生长与健康。     

吉富罗非鱼对饲料中苯丙氨酸的需要量

分别用含6种水平(质量比分别为0.78%、0.95%、1.09%、1.34%、1.51%和1.72%)苯丙氨酸(phenylalanine,Phe)的等氮等能(粗蛋白30.10%,总能17.73 MJ/kg)饲料,在池塘网箱中(实验期间水温为24~32℃)饲喂初始体重为(52.70±1.80)g的吉富罗非鱼60 d,考察饲料Phe对吉富罗非鱼(GIFT,Oreochromis niloticus)生长性能、饲料系数、体成分、部分血清生化指标及前肠消化酶活性的影响,以期获得吉富罗非鱼对饲料苯丙氨酸的需要量。结果表明,随着饲料中Phe水平的升高,吉富罗非鱼的增重率、特定生长率、蛋白质效率、蛋白质沉积率、肥满度、肝体比和脏体比均呈现先上升后下降的趋势,饲料系数呈现先下降后上升的趋势;全鱼粗脂肪和全鱼灰分含量显著上升(P0.05),肌肉灰分含量显著下降(P0.05)。饲料中Phe对全鱼水分和粗蛋白质、肌肉水分、肌肉粗蛋白质和肌肉粗脂肪含量无显著性影响(P0.05);各实验组的肌肉氨基酸含量差异不显著(P0.05)。饲料中Phe显著影响血清中谷丙转氨酶活性,甘油三酯、总胆固醇和葡萄糖的含量(P0.05),对谷草转氨酶活性无显著性影响(P0.05);Phe显著影响肠蛋白酶、肠脂肪酶和肠Na~+-K~+-ATP酶活性(P0.05),而对肠淀粉酶活性影响不显著(P0.05)。以增重率、饲料系数和蛋白质效率为评价指标,通过二次回归分析可知,吉富罗非鱼对饲料中Phe需要量为1.17%~1.21%,占饲料蛋白质的3.89%~4.02%。本研究结果为合理配制吉富罗非鱼配合饲料提供了理论依据。     

饲料菜粕水平对吉富罗非鱼幼鱼生长、肝脏组织结构和部分非特异性免疫指标的影响

分别用15.0%(对照组)、30.0%、45.0%、60.0%、75.0% 的菜粕配制5种等氮(粗蛋白质为34.0%)等能(总能为19.2 kJ/g)饲料,饲养吉富罗非鱼幼鱼［初始体质量(4.82±0.46) g］10周,考察饲料中不同菜粕水平对吉富罗非鱼生长、肝脏组织结构和部分非特异性免疫指标的影响。结果表明,吉富罗非鱼的增重率、特定生长率、饲料效率和蛋白质效率随着菜粕水平的增加呈下降趋势,且60.0%和75.0%组显著低于对照组(P<0.05),30.0% 和45.0% 组与对照组无显著性差异(P>0.05);各处理组之间的肝体比、脏体比和成活率无显著性差异(P>0.05)。吉富罗非鱼全鱼营养成分,60.0% 组粗蛋白质含量显著高于对照组(P<0.05),60.0%组粗脂肪含量显著低于30.0%(P<0.05),各处理组水分和灰分无显著性差异(P>0.05)。吉富罗非鱼肝细胞核偏移和空泡变性的数量随着菜粕水平的增加逐渐增加,肝脏组织结构受损程度加剧。血清碱性磷酸酶活性随着菜粕水平的增加不断升高,且75.0%组显著高于对照组(P<0.05),血清超氧化物岐化酶活性随着菜粕水平的增加而下降,60.0%组最低,与对照组差异显著(P<0.05)。在本试验条件下,吉富罗非鱼幼鱼饲料中菜粕的使用量不宜超过45.0%。     

饲料糖水平对不同食性鱼类生长及葡萄糖耐受能力的影响

为研究饲料糖水平对不同食性鱼类生长、血浆生化指标、肝/肌糖原的影响及葡萄糖耐受能力的影响,本实验以不同食性的吉富罗非鱼、卵形鲳鲹和军曹鱼为研究对象,糊精为糖源,三种鱼各设置低、中、高（CL、CM、CH;吉富罗非鱼：20%、30%、40%;卵形鲳鲹：13%、26%、39%;军曹鱼：12%、24%、36%）3个不同饲料糖添加水平,依次为进行8周的饲养实验并进行葡萄糖注射实验。结果显示：饲料中不同糖水平对吉富罗非鱼成活率没有显著影响（P>0.05）;饲料系数随饲料糖水平的升高呈现先下降后升高趋势,以CL组最高（P<0.05）;增重率与特定生长率最高值均出现在CH组中,显著高于CL组（P<0.05）。卵形鲳鲹和军曹鱼CH组存活率均显著低于其他各组（P<0.05）;而增重率与特定生长率则均为CM组显著最高（P<0.05）;三种鱼饲料系数随着饲料糖水平的升高呈现先下降后升高趋势,均以CM组最低,分别为1.47（吉富罗非）、1.61（卵形鲳鲹）和1.49（军曹鱼）。饲料中不同糖水平对不同食性鱼类糖代谢相关生化指标有不同程度的影响。随着饲料中糖水平的上升,罗非鱼CH组糖代谢指标均显著高于其他各组（P<0.05）。卵形鲳鲹和军曹鱼CH组血糖、胰岛素、肝/肌糖原、甘油三酯均为最高;军曹鱼CM组肝/肌糖原和甘油三酯均显著高于其他各组（P<0.05）。葡萄糖耐受实验结果显示注射葡萄糖后：（1）卵形鲳鲹组和罗非鱼组在1 h血糖水平达峰值（P<0.05）,并且均在12 h恢复到注射前水平;而军曹鱼组在3 h达血糖峰值后直至24 h才回到注射前水平。（2）军曹鱼组与罗非鱼组血浆胰岛素水平缓慢上升,至3 h达最高水平（P<0.05）,而卵形鲳鲹组在1 h内显著下降（P<0.05）。（3）卵形鲳鲹组与罗非鱼组肝糖原水平缓慢上升,分别在3 h、6 h达峰值（P<0.05）,而军曹鱼组在1 h内呈下降趋势。（4）罗非鱼组与卵形鲳鲹组甘油三酯水平分别在3 h、6 h达峰值（P<0.05）,而军曹鱼组在1 h内显著下降（P<0.05）。本研究表明,饲料糖水平对对三种食性鱼类生长、糖代谢生化指标、葡萄糖利用和耐受能力具有不同程度的影响,杂食性罗非鱼可比肉食性鱼类更好地利用膳食糖物质。葡萄糖耐受能力则以杂食性吉富罗非鱼为最强,卵形鲳鲹次之,军曹鱼葡萄糖耐受能力最低。     

34 ℃水温下吉富罗非鱼对饲料脂肪的需求量

为研究34 ℃水温下吉富罗非鱼对饲料脂肪的需求量,选用初始体质量为(50.88±1.57) g的吉富罗非鱼360尾,随机分成6组(每组设3个重复,每重复20尾),饲喂脂肪含量分别为0.22%(对照组)、2.83%、4.98%、7.45%、9.23%和12.47%的6种纯化饲料,在34 ℃水温下饲养56 d后,测定并分析了吉富罗非鱼的生长性能、体成分、部分血清生化和肝脏脂肪代谢酶活性等指标。结果显示,随饲料脂肪水平升高,吉富罗非鱼增重率、特定生长率、蛋白质效率与蛋白质保留率均呈现先上升后下降的趋势,饲料系数和摄食率呈现相反的趋势;12.47%实验组肝体比显著高于其他实验组,其他指标组间无显著性差异。饲料脂肪水平对吉富罗非鱼的成活率无显著影响。对照组全鱼粗脂肪含量显著低于其他实验组;当饲料脂肪含量为7.45%~12.47%时,肌肉粗脂肪含量显著高于对照组;肝脏粗脂肪含量在饲料脂肪含量为2.83%~9.23%时较对照组显著降低。血清甘油三酯和总胆固醇随饲料脂肪水平升高呈现先下降后上升的趋势;肝脏脂肪酶和脂蛋白酯酶活性随脂肪水平的增加呈上升趋势,在12.47%组达到最大值;肝脂酶的活性呈先上升再下降最后趋于稳定的趋势,在脂肪水平为2.83%时最高, 显著高于其他各组。经回归分析,在34 ℃水温下,吉富罗非鱼要获得最佳的增重率、蛋白质效率和最低饲料系数对饲料脂肪的需求量分别为4.92%、5.67%和6.49%。     

饲料中添加中性蛋白酶对吉富罗非鱼生长和消化功能的影响

在吉富罗非鱼(Oreochromis niloticus)基础饲料中添加中性蛋白酶,添加量分别为0.00%、0.05%、0.1%、0.15%、0.2%和0.25%,研究添加后对吉富罗非鱼生长和消化功能的影响。结果表明,在饲料中添加0.1%~0.25%的中性蛋白酶,吉富罗非鱼的相对增重率和特定生长率显著提高,饲料系数显著降低(P<0.05);添加0.1%~0.2%的中性蛋白酶,显著提高饲料干物质表观消化率和粗蛋白表观消化率(P<0.05);添加量为0.1%~0.15%时,肝胰脏蛋白酶显著高于对照组(P<0.05),添加量为0.15%时,肠道蛋白酶活性显著提高(P<0.05)。综合鱼体相对增重率、特定生长率、饲料系数、消化器官消化酶活性等各项指标,吉富罗非鱼饲料中中性蛋白酶的添加量以饲料的0.1%~0.2%为宜。     

玉米蛋白粉替代鱼粉对大菱鲆摄食、生长及体组成的影响

以鱼粉和玉米蛋白粉作蛋白源,配制6种等氮等能的饲料。其中5种饲料(C0、C12、C25、C38和C50.5)分别含有0%、12%、25%、38%和50.5%的玉米蛋白粉以替代相应的鱼粉蛋白。其余1种饲料(C50.5CAA)是在饲料C50.5基础上补充1.8%晶体氨基酸混合物(L-lysine:1.2%,L-arg:0.6%)。经7周的生长试验,结果表明随着饲料中玉米蛋白粉替代水平的升高,大菱鲆(12.51±0.02)g的摄食率、特定生长率、饲料效率和蛋白质效率均显著下降。饲料中玉米蛋白粉含量为50.5%时,大菱鲆摄食率显著低于其他处理组(P<0.05)。当饲料中玉米蛋白粉含量超过25%时,大菱鲆特定生长率显著低于对照组(C0)(P<0.05)。当饲料中玉米蛋白粉含量超过38%时,饲料效率和蛋白质效率与对照组(C0)相比显著下降(P<0.05)。C50.5CAA组的摄食率、特定生长率和蛋白质效率与C50.5组相比都有升高的趋势,但差异不显著。而饲料中添加晶体氨基酸显著提高了大菱鲆的饲料效率(P<0.05)。饲料中玉米蛋白粉替代鱼粉对大菱鲆鱼体水分、粗蛋白、粗脂肪及灰分含量均无显著影响。饲料中玉米蛋白粉替代鱼粉对大菱鲆血清甘油三酯和尿素氮含量也不产生显著影响,然而,随着饲料中玉米蛋白粉含量升高,血清总胆固醇含量显著下降(P<0.05)。     

注射葡萄糖对吉富罗非鱼血浆生化指标、胰岛素和糖酵解关键酶的影响

研究注射葡萄糖对吉富罗非鱼(Oreochromis miloticus)生化指标、胰岛素和糖酵解酶的影响。选取体质量约80 g的吉富罗非鱼150尾,随机分为2个实验组,对照组腹腔注射0.7%的无菌生理盐水,处理组按照30 mg/100 g(体质量)的剂量腹腔注射葡萄糖。结果表明:(1)吉富罗非鱼在注射葡萄糖后1 h血糖达到最高水平,而后显著下降(P<0.05),3 h后降低到正常水平。注射葡萄糖可显著提高胆固醇的含量(P<0.05),并显著降低谷草转氨酶水平(P<0.05),但对血浆蛋白、甘油三酯和谷丙转氨酶水平没有显著影响(P>0.05)。(2)肝糖原在葡萄糖注射后的6 h达到最高水平,而后显著下降(P<0.05),肌糖原没有发生变化。(3)血浆和肌肉中的胰岛素均在葡萄糖注射后的3 h达到最高水平,而后显著下降(P<0.05),而肝中的胰岛素水平没有发生变化。(4)丙酮酸激酶的活力在葡萄糖注射后6h达到最高水平(P<0.05),己糖激酶的活力在注射葡萄糖后没有发生变化。结果表明,注射葡萄糖可显著提高吉富罗非鱼血糖水平,且维持时间较长,胰岛素含量和丙酮酸激酶(PK)活力的提高均相对延迟,而己糖激酶活力的不足又限制了葡萄糖的酵解反应,从而引起血浆胆固醇升高,并伴有持续的血糖和肝糖原升高,从而产生营养胁迫的生理反应,加重鱼类对葡萄糖的代谢负担。     

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。     

吉富罗非鱼对饲料亚油酸的需要量

选用初始体重为(60.98±3.82)g的吉富罗非鱼(Oreochromis niloticus)630尾,随机分成7组(每组设3个重复,每个重复30尾),饲喂亚油酸含量分别为0.07%(对照组)、0.36%、0.61%、1.03%、2.00%、3.00%和4.15%的7种半纯化等能等氮饲料10周。结果表明,鱼体增重率、饲料效率、蛋白质效率和蛋白质沉积率均在亚油酸水平为1.03%时较对照组差异显著(P0.05),且均在饲料亚油酸水平为2.00%时达到最大。经二次回归分析,饲料亚油酸水平为2.49%和2.66%时吉富罗非鱼分别获得最大增重率和最高饲料效率。通过折线回归发现饲料亚油酸水平为1.02%时,吉富罗非鱼获得最大蛋白沉积。肝体比和脏体比均随亚油酸水平的升高而升高,当饲料亚油酸含量为0.61%~4.15%时显著高于对照组(P0.05)。亚油酸添加组的肌肉粗脂肪含量显著高于对照组(P0.05);当饲料亚油酸含量为1.03%~4.15%时,肝和全鱼粗脂肪含量显著高于对照组(P0.05)。随饲料亚油酸水平升高,血清甘油三酯和总胆固醇变化趋势一致,呈现先下降后上升的趋势,经二次回归分析亚油酸水平为1.63%时血清甘油三酯含量最低;各亚油酸添加组的血清高密度脂蛋白胆固醇含量显著高于对照组,且在饲料亚油酸含量为1.13%时达到最大(P0.05);当饲料亚油酸水平为1.03%~4.15%时,血清低密度脂蛋白胆固醇含量显著低于对照组(P0.05)。随饲料中饱和脂肪酸(∑SFA)含量下降,吉富罗非鱼肌肉和肝脏∑SFA含量均呈下降的趋势;随饲料亚油酸水平增加,肌肉和肝脏的n-6多不饱和脂肪酸(∑n-6 PUFA)含量呈上升趋势,肌肉和肝脏的∑n-3 PUFA含量呈下降趋势。综上所述,初始体重为(60.98±3.82)g的吉富罗非鱼饲料亚油酸需要量为1.02%~2.66%。     

Performance,body compositions,input and output of nitrogen and phosphorus in Siberian sturgeon,Acipenser baerii Brandt,as affected by dietary animal protein blend replacing fishmeal and protein levels

An 8‐week growth trial was conducted using a 2 × 3 factorial design to evaluate the effect of substitution of fishmeal (FM) by rendered animal protein blend [APB, comprised of 400 g kg^?1 poultry by‐product meal, 350 g kg^?1 meat and bone meal, 200 g kg^?1 hydrolysed feather meal (HFM) and 50 g kg^?1 spray‐dried blood meal] in diets of Siberian sturgeon, Acipenser baerii Brandt. Two isoenergetic control diets were formulated to contain two different protein levels [high‐protein control (400 g kg^?1), with 483 g kg^?1 of FM] and [low‐protein control (360 g kg^?1), with 400 g kg^?1 of FM]. At each protein level, dietary FM protein was replaced by APB at 75% and 100% levels and supplemented with crystallized essential amino acid under ideal protein concept. The six diets were named as HC, HAPB75, HAPB100, LC, LAPB75 and LAPB100, respectively. No significant differences were found in weight gain rate (WGR) and specific growth rate (SGR), but fish fed with the low‐protein diets showed higher feed intake and feed conversion ratio. Plasma growth hormone and insulin‐like growth factors I of each group were not significantly different (P > 0.05). The whole‐body composition and liver composition were not affected by dietary protein levels, replacement or their interaction. Muscle protein and lipid contents of fish fed with diet LAPB100 were significantly lower than those of HC group. Digestibility of nitrogen (N) and phosphorus (P) were reduced with higher APB inclusion levels, but productive N and P values of all groups were not different. Lower N and P intake induced lower nutrients losses (P < 0.05). The results suggested that dietary protein level could be reduced to 360 g kg^?1 from 400 g kg^?1 without affecting WGR or SGR and significantly reduced nutrients lose. Furthermore, dietary FM protein can be totally replaced by APB in feed formulation either at 400 g kg^?1 or at 360 g kg^?1 protein level.     

The effects of dietary protein and lipid on growth and body composition of juvenile and sub-adult red snapper, Lutjanus campechanus (Poey, 1860)

To allow for the initial identification of practical diet formulations for red snapper culture, the present study was conducted to evaluate the effects of feeding varying levels of dietary protein and lipid on growth and body composition of juvenile and sub‐adult red snapper. Twelve diets were formulated to contain varying levels of dietary protein and lipid. In trial 1, juvenile red snapper (initial mean weight 5.9 g) were offered diets with graded levels of dietary protein (32%, 36%, 40%, 44%) and practical energy to protein ratios. In trial 2, juvenile red snapper (initial mean weight 8.64 g) were offered isonitrogenous diets (44% protein) containing graded levels of dietary lipid (8%, 10%, 12%, 14%). Sub‐adult fish (initial mean weight 151.5 g) were used in trial 3 and maintained on diets similar to those of trial 1 (32–44% protein). Sub‐adult fish (initial mean weight 178.3 g) in trial 4 were offered isonitrogenous diets containing 32% dietary protein and graded levels of dietary lipid (6%, 8%, 10%, 12%). There were no significant differences in growth, feed efficiency ratio (FER) or survival in juvenile fish. Juvenile fish offered 32% dietary protein exhibited a significantly greater (P=0.0497) protein conversion efficiency (PCE) than fish offered a diet containing 44% dietary protein. Juvenile fish in trial 2 also had significantly higher (P=0.005) intraperitoneal fat ratios (IPFRs) at 14% dietary lipid than fish offered diets containing 8–10% dietary lipid, and displayed trends towards greater protein as a percent of whole‐body composition at 8–10% dietary lipid. Sub‐adult snapper in trials 3 and 4 showed no significant differences in growth, FER or survival. However, in trial 4 there was a general trend towards increased % weight gain (P=0.0615), FER (P=0.0601) and final mean weight (P=0.0596) with increasing levels of dietary lipid. Fish in trial 4 offered 6% dietary lipid also had significantly lower (P=0.0439) IPFR and PCE (P=0.0188) than fish offered 12% dietary lipid. Based on data obtained from these trials, inclusion of dietary protein at levels of 32–36% appears sufficient to support growth. For this level of protein, dietary lipid should be ～10% in order to meet the energetic demands of the fish and to spare dietary protein for growth.     

Growth,Feed Conversion,and Nutrient Retention Efficiency of African Catfish,Clarias gariepinus, (Burchell) Fingerling Fed Diets with Varying Levels of Protein

Growth, feed conversion, and nutrient retention efficiencies of African catfish fingerling, Clarias gariepinus (5.22 ± .07 cm; 8.22 ± 0.03 g), fed diets with varying levels of protein were assessed by feeding seven casein/gelatin based isocaloric (17.62 kJ/g GE) experimental diets with graded levels of dietary protein (20%, 25%, 30%, 35%, 40%, 45%, and 50% of the diet) to triplicate groups of fish to apparent satiation for eight weeks. Effects of feeding these diets on live weight gain (LWG%), feed conversion ratio (FCR), protein efficiency ratio (PER), protein retention efficiency (PRE%), and energy retention efficiency (ERE%) were assessed. Maximum LWG% (867%), PER (2.01), highest PRE (32%), ERE (69%), best FCR (1.39), and maximum body protein were recorded in fish fed diet containing 35% protein. On the basis of the second-degree polynomial regression analysis of the above response variables, it is recommended that the inclusion of protein in the range of 34.4%–39.6% is optimum for maximizing growth potential, feed conversion, and nutrient retention in African catfish fingerling, Clarias gariepinus.     

Effect of dietary protein and lipid levels and protein to energy ratios on growth, survival and body composition of the mangrove red snapper, Lutjanus argentimaculatus (Forsskal 1775)

The approximate levels of dietary protein and energy that would sustain good growth and survival of the mangrove red snapper Lutjanus argentimaculatus (Forsskal) were determined in two feeding experiments. In the preliminary experiment, six fish meal‐based diets were formulated to contain three protein levels (35%, 42.5% and 50%) and two lipid levels (6% and 12%) for each protein, with dietary energy ranging from 14.6 MJ kg^?1 to 20.5 MJ kg^?1. The protein to energy (P/E) ratios of diets ranged from 20.6 mg protein kJ^?1 to 27.5 mg protein kJ^?1. Diets were fed for 100 days to triplicate groups of snappers with an average initial weight of 24.8 ± 0.4 g. No significant interaction between different levels of protein and lipid was observed. Survival rates (93.8% to 100%), feed conversion ratios (FCR) (2.61–3.06) and condition factors (K) were not affected by different dietary treatments. Regardless of lipid level, fish fed 50% protein diets had a significantly higher specific growth rate (SGR) than fish fed the 35% protein diets, but not compared with the 42.5% diets (P < 0.05). Increasing lipid to 12% in all protein levels resulted in no improvement in growth over the 6% level. Fish body moisture did not vary while lipid levels based on dry matter were high (27.9% to 33.7%). Snapper appear to require more than 40% dietary protein and a high dietary energy level for good growth. In the second experiment, fish (21.1 ± 0.1 g) in four replicate groups were fed for 94 days with three diets (39%, 44% and 49% protein with P/E ratios of 21.1, 23.3 and 25.5 mg protein kJ^?1 respectively) containing similar dietary energy levels of about 19 MJ kg^?1. Average final weight, SGR and FCR were significantly higher in diets containing 44% and 49% protein diets (P > 0.05). There were no differences in survival rates, protein efficiency ratio (PER) and nutrient composition of snapper flesh. All fish had fatty livers. Results indicated that the diet containing 44% protein with a P/E ratio of 23.3 mg protein kJ^?1 was optimum for snapper growth under the experimental conditions used in the study.     

Quantitative changes in a serum protein,AS, during the life cycle of the lamprey,Petromyzon marinus L.

The electrophoretically fastest migrating protein in ammocoete serum, AS protein, was isolated and found to be an acidic glycoprotein with a molecular weight of 140,000 Daltons. Purified AS was injected into rabbits to produce a monospecific antiserum that was used in rocket immunoelectrophoresis to quantitate AS at different periods in the life cycle. AS was found to constitute approximately 70% of total serum protein in the ammocoete, remained at about the same value during transformation, and was reduced to 38% of total serum protein in the juvenile adult. In both male and female upstream migrant animals, AS was less than 0.5% of total serum protein. When juveniles were acclimated to seawater over a 10 week period, it was found that their AS level was reduced by 92% to 3.8% of total serum protein. These results are discussed in relation to changes in other serum proteins at various intervals of the lamprey life cycle.     

Protein synthesis,growth and energetics in larval herring (Clupea harengus) at different feeding regimes

Rates of growth, protein synthesis and oxygen consumption were measured in herring larvae, Clupea harengus, in order to estimate the contribution that protein synthesis makes to oxygen consumption during rapid growth at 8°C. Protein synthesis rates were determined in larvae 9 to 17 d after hatching. Larvae were bathed in ³H phenylalanine for several hours and the free pool and protein-bound phenylalanine specific radioactivities were determined.Fractional rates of protein synthesis increased 5 to 11 fold with feeding after a period of fasting. Efficiencies of retention of synthesized protein were approximately 50% during rapid growth. Rapid growth in herring larvae thus appears to be characterized by moderate levels of protein turnover similar to those obtained for larger fish. Increases in growth rate occurred without changes in RNA concentration, i.e., the larvae increased the efficiency of RNA rapidly. Oxygen consumption rates were not correlated with growth rates. Protein synthesis was estimated to account for 79% of the oxygen consumption, and energy costs of protein synthesis were high, i.e., about 98 mmole O₂ g^–1 protein synthesized.     

Fast growth, protein turnover and costs of protein metabolism in yolk-sac larvae of the African catfish (Clarias gariepinus)

In fish larvae the costs of rapid growth may be accommodated by a decrease in the rate of protein turnover or by a reduction in the costs of protein synthesis. Protein growth, synthesis and degradation were measured in yolk-sac larvae of Clarias gariepinus and the costs of protein synthesis and protein growth were estimated. Growth rates were over 100% protein weight day^-1. Protein synthesis retention efficiency (retained protein per unit of synthesis) was estimated to be 69.6%, a value comparable to that of larger fish. The larvae used 43% of their oxygen consumption for protein synthesis. Nevertheless, protein synthesis costs were close to theoretical minima. Therefore, the high growth rates of catfish yolk-sac larvae seem to be possible through minimisation of the costs of protein synthesis. These low costs are associated with high rates of protein synthesis (138%protein weight day^-1), and elevated RNA concentrations (107 µg RNA mg^-1protein), which together suggest very high RNA efficiencies (12.9 g protein synthesized g^-1RNA day^-1).     

Nitrogen,Phosphorus, and Carbon Concentrations in Some Common Aquaculture Feeds

Nitrogen, phosphorus, and carbon concentrations were measured from 203 samples of starter, fingerling, and grower aquaculture feeds from several countries and for several common species. The feed protein concentrations reported by manufacturers often were slightly greater than the measured crude protein concentrations. The correlation coefficients (R²) between feed nitrogen and carbon concentrations were less than 0.50, and nitrogen and phosphorus concentrations in feed were not correlated. There were considerable differences in elemental concentrations among feeds, but the overall averages for carbon, nitrogen, and phosphorus concentrations, respectively, were as follows: starter feed 41.36, 7.78, and 1.57%; fingerling feed 39.75, 5.95, and 1.36%; grower feed 39.97, 5.36, and 1.22%. Concentrations of carbon, nitrogen, and phosphorus in feeds are required in estimating the pollution potential of aquaculture facilities. The crude protein concentration – if provided by the manufacturer – can be used to estimate nitrogen concentration in feed, but carbon and phosphorus concentrations should be measured.     

Evaluation of growth, feed utilization, and economics of hybrid tilapia, Oreochromis niloticus×Oreochromis aureus, fed diets containing different protein sources in combination with distillers dried grains with solubles

A feeding trial was conducted in aquaria with juvenile hybrid tilapia (Oreochromis niloticus×Oreochromis aureus) to evaluate the use of different protein sources in combination with distillers dried grains with solubles (DDGS). Twelve 110‐L glass aquaria were stocked with 28 juvenile (2.7±0.5‐g) hybrid tilapia per aquarium. Three replicate aquaria were randomly assigned to each of the four dietary treatments. Diets were isonitrogenous and isocaloric. The control diet contained 12% fish meal and 41% soybean meal as the primary protein sources (Diet 1). Each experimental diet contained 30% DDGS by weight, in combination with 8% fish meal and 34% soybean meal (Diet 2), 26% meat and bone meal (MBM), and 16% soybean meal (Diet 3), or 46% soybean meal alone (Diet 4). Fish were fed to apparent satiation twice a day for 10 weeks. There were no significant differences (P>0.05) in average weight gain, specific growth rate (SGR), feed conversion ratio (FCR), and protein efficiency ratio (PER) among tilapia fed Diets 1, 2, and 3. Fish fed Diet 4 had significantly lower (P<0.05) average weight gain, SGR, and PER than fish fed Diets 1 and 3. Relative cost per unit weight gain for Diets 1, 2, and 3 were statistically similar (P>0.05), while cost per unit weight gain for Diet 4 was significantly higher (P<0.05) than other diets. Diet 3 represented approximately a 20% cost savings compared with the control diet, with no reduction in growth. This study indicates that diets without fish meal containing 30% DDGS in combination with MBM and soybean meal provide good growth in tilapia. A diet without animal protein did not support acceptable growth.