木薯粉对罗非鱼生长、饲料利用和鱼体营养成分的影响

选择健康的吉富罗非鱼(体重1.29±0.25 g)为实验鱼,配制五种木薯粉含量分别为0%、10%、20%、30%和40%的等氮(粗蛋白为32%)、等能(总能为16 kJ·g-1)实验饲料,饲喂罗非鱼56 d,每饲料组设三个重复,研究不同含量木薯粉对吉富罗非鱼生长、饲料利用及全鱼营养成分的影响.结果表明:(1)木薯粉能提高罗非鱼的增重和蛋白质效率,其中以40%木薯粉组的效果最佳,其增重率、蛋白质效率和饲料系数分别为1470.99%(P＜0.05)、2.36(P＜0.05)和1.27(P＜0.05).(2)40%木薯粉组的干物质和蛋白质的表观消化率分别较对照组提高13.87%(P＜0.05)和7.93%(P＜0.05).(3)40%木薯粉组的全鱼粗蛋白、粗灰分分别较对照组显著提高7.07%(P＜0.05)和8.78%(P＜0.05),粗脂肪降低了13.00%(P＜0.05).     

不同木薯变性淀粉对鲤鱼生长及糖代谢的影响

选用初始体质量为(55.73±3.55)g,健康状况良好的鲤鱼1080尾,随机分成6个组,每组3个重复,每个重复60尾,进行为期8周的养殖试验,养殖试验在淡水浮式网箱中进行。试验结果显示,预糊化木薯淀粉组的质量增加率、特定生长率及蛋白质效率最高,饲料系数最低;肝体比及肥满度分别以预糊化木薯淀粉组为最大,而肝糖原含量以预糊化木薯淀粉组为最小,但均与原木薯淀粉组及木薯醋酸酯淀粉组差异不显著(P0.05)。预糊化木薯淀粉作为饲料糖源时显著提升了肠道中淀粉酶活性的活性(P0.05)。不同淀粉组的血糖、胰岛素、生长激素和类胰岛素,生长因子浓度存在显著性差异(P0.05),且均为预糊化木薯淀粉组最高,不同淀粉组的生长激素也有显著差异(P0.05),以预糊化木薯淀粉组最低。各淀粉组的6-磷酸果糖-1-激酶活性存在显著性差异(P0.05),预糊化木薯淀粉组最高;各淀粉组的糖异生关键酶活性存在显著性差异(P0.05),均为预糊化木薯淀粉组最低。本试验结果表明,鲤鱼对预糊化木薯淀粉的利用效果优于原木薯淀粉及木薯醋酸酯淀粉。     

肉松粉、羽毛粉和肉骨粉替代鱼粉养殖奥尼罗非鱼的效果研究

试验研究了肉松粉、羽毛粉和肉骨粉替代鱼粉池塘养殖奥尼罗非鱼的效果研究。24 000尾(349±28.3)g奥尼罗非鱼分为4组,每组设计3个平行试验区域,每2 000尾饲养于2×667 m2左右的实验区域中。对照组和1、2、3试验组日粮分别以鱼粉、肉松粉、羽毛粉和肉骨粉设计蛋白质水平为28%左右,消化能为2 670～2 810 Kcal/kg。在水温(28.2±2.8)℃饲养60 d。试验结果:①奥尼罗非鱼的相对生长率,食物转化率肉松粉组鱼粉组肉骨粉组羽毛粉组,差异显著(P0.05)。由于单位鱼成本不同,肉松粉组养殖效益为对照组的132.46%,肉骨粉组为对照组的96.60%,羽毛粉组为对照组的80.51%。②奥尼罗非鱼体水分,灰分含量差异不显著(P0.05);蛋白质含量鱼粉组肉松粉组肉骨粉组羽毛粉组,鱼粉组显著性高于肉骨粉和羽毛粉组(P0.05);脂肪含量肉骨粉组羽毛粉组肉松粉组鱼粉组,前3组显著性高于鱼粉组(P0.05)。③奥尼罗非鱼肥满度,脏体比,肝体比无显著性差异(P0.05),仅肉骨粉组肠脂比及肝脂肪含量最高,羽毛粉组最低,显著性差异(P0.05)。在池塘养殖中,饲料中使用肉松粉替代鱼粉可明显降低成本,提高经济效益。在罗非鱼饲料中使用部分肉骨粉和羽毛粉是安全的。     

非淀粉多糖酶对奥尼罗非鱼生长及水质的影响

选用体重约60 g的奥尼罗非鱼560尾,随机分成4个试验组,每组7个重复,每重复20尾,分别添加不同梯度水平的液体酶制剂(0、0.01%、0.02%、0.04%)。试验结果表明:奥尼罗非鱼饵料中添加非淀粉多糖酶对罗非鱼的特定生长率、饵料系数等均有显著影响(P<0.05),0.02%组和0.04%组的特定生长率比对照组分别提高10.61%和11.36%,0.02%组和0.04%组的饵料系数比对照组分别降低16.13%和18.99%;罗非鱼饵料中添加非淀粉多糖酶显著降低了水中氨氮含量,提高了水中溶氧量。     

木薯粉在罗非鱼饵料中的适口性研究

选择健康的吉富罗非鱼为试验鱼,比较不同水平木薯粉之间的诱食效果以及木薯粉与豆粕、次粉的适口性,评价木薯粉在罗非鱼饵料中的应用效果。结果表明,(1)40%、30%木薯粉组的诱食活性显著高于10%、20%木薯粉组(p0.01),40%与30%木薯粉之间没有显著差异(p0.05)。(2)罗非鱼对木薯粉与豆粕、次粉的适口性依次为豆粕木薯次粉。     

不同配合饲料对南方鲇幼鱼体组成的影响

主要探索不同饲料组成对鱼体组成的影响.将360尾南方鲇(Silurus meridionalis Chen)幼鱼随机分成24组,饲养于24个水泥池中;共设计了21种饲料;实验持续了40 d.结果表明:(1)不同营养素水平,对鱼体中的蛋白质沉积无明显影响;肌肉中脂肪水平随着饲料中脂肪和碳水化合物(CBH)水平的增加而增加;CBH含量为33%时,肌肉中的CBH的沉积量显著高于其他几个组(P<0.05);(2)脏体比和肠脂比随着饲料中脂肪水平升高而升高,脂肪水平9%～15%,肝脏中沉积的脂肪含量随着饲料中脂肪含量的增加而增加,添加CBH含量为33%的饲料时,肝脏中糖原的沉积含量显著的高丁其他几个CBH含量的组(P<0.05).     

两种甘薯饲料原料的营养成分及其对仿刺参(Apostichopus japonicus)摄食与生长的影响

在刺参配合饲料中添加6个比例(10%、20%、30%、40%、50%、60%)的甘薯块根粉与甘薯蔓茎粉,测定两种甘薯饲料原料的营养成分及其对仿刺参摄食与生长的影响。结果显示,甘薯块根粉中粗蛋白含量为10.01%,甘薯蔓茎粉中粗蛋白含量为5.54%;每100 g甘薯块根与蔓茎粉中氨基酸总量分别为7.33 g和4.37 g。在30 d的实验期间,投喂添加甘薯块根粉饲料的实验组仿刺参平均体重随实验时间呈上升趋势,实验结束时,10%和20%组特定生长率(SGR)显著高于对照组(P0.05),30%组SGR与对照组差异不显著(P0.05)。投喂添加10%甘薯蔓茎粉的实验组仿刺参SGR与对照组差异不显著(P0.05),其余各组SGR均低于对照组(P0.05)。投喂添加10%、20%甘薯块根粉饲料的实验组仿刺参食物转化率(FCE)显著高于对照组(P0.05),投喂添加10%甘薯蔓茎粉饲料的实验组FCE与对照组差异不显著(P0.05),其余各实验组仿刺参FCE显著低于对照组(P0.05)。结果表明,当甘薯块根粉和甘薯蔓茎粉添加比例分别低于30%和10%时,可满足刺参的营养需求,提高饲料利用效率,保证并促进仿刺参的摄食与生长。     

两种甘薯饲料原料的营养成分及其对仿刺参(Apostichopus japonicus)摄食与生长的影响

在刺参配合饲料中添加6个比例(10％、20％、30％、40％、50％、60％)的甘薯块根粉与甘薯蔓茎粉,测定两种甘薯饲料原料的营养成分及其对仿刺参摄食与生长的影响.结果显示,甘薯块根粉中粗蛋白含量为10.01％,甘薯蔓茎粉中粗蛋白含量为5.54％;每100 g甘薯块根与蔓茎粉中氨基酸总量分别为7.33 g和4.37 g.在30 d的实验期间,投喂添加甘薯块根粉饲料的实验组仿刺参平均体重随实验时间呈上升趋势,实验结束时,10％和20％组特定生长率(SGR)显著高于对照组(P＜0.05), 30％组SGR与对照组差异不显著(P＞0.05).投喂添加10％甘薯蔓茎粉的实验组仿刺参SGR与对照组差异不显著(P＞0.05),其余各组SGR均低于对照组(P＜0.05).投喂添加10％、20％甘薯块根粉饲料的实验组仿刺参食物转化率(FCE)显著高于对照组(P＜0.05),投喂添加10％甘薯蔓茎粉饲料的实验组FCE与对照组差异不显著(P＞0.05),其余各实验组仿刺参FCE显著低于对照组(P＜0.05).结果表明,当甘薯块根粉和甘薯蔓茎粉添加比例分别低于30％和10％时,可满足刺参的营养需求,提高饲料利用效率,保证并促进仿刺参的摄食与生长.     

饲料中添加甘薯(Ipomoea batatas)块根与茎蔓对刺参(Apostichopus japonicus)生长和非特异性免疫力的影响

在刺参(Apostichopus japonicus)配合饲料中添加不同比例(10％、20％、30％、40％、50％、60％)的甘薯块根粉与甘薯茎蔓粉,测定了添加2种甘薯饲料成分对刺参生长和非特异性免疫力的影响.结果显示,在50 d实验期间,投喂添加甘薯块根粉饲料的实验组刺参平均体重随实验时间呈上升趋势,实验结束时,添加20％甘薯块根粉组终末体重显著高于对照组(P＜0.05),10％、30％组特定生长率(SGR)与对照组差异不显著(P＞0.05);投喂添加10％甘薯茎蔓粉的实验组刺参SGR与对照组差异不显著(P＞0.05),其余各组SGR均低于对照组(P＜0.05).投喂添加10％、20％甘薯块根粉饲料的实验组刺参体腔液中过氧化氢酶(CAT)、酸性磷酸酶(ACP)、碱性磷酸酶(AKP)均显著高于对照组(P＜0.05);投喂添加10％甘薯茎蔓粉饲料的实验组ACP显著高于对照组(P＜0.05),刺参体腔液中的溶菌酶(LZM)、总超氧化物歧化酶(T-SOD)、CAT和AKP与对照组差异不显著(P＞0.05).研究表明,当甘薯块根与茎蔓的添加比例分别在30％和20％以下时,可满足刺参的营养需求,促进或保证刺参的生长,提高刺参免疫能力.     

饲料中添加甘薯(Ipomoea batatas)块根与茎蔓对刺参(Apostichopus japonicus)生长和非特异性免疫力的影响

在刺参(Apostichopus japonicus)配合饲料中添加不同比例(10%、20%、30%、40%、50%、60%)的甘薯块根粉与甘薯茎蔓粉,测定了添加2种甘薯饲料成分对刺参生长和非特异性免疫力的影响。结果显示,在50 d实验期间,投喂添加甘薯块根粉饲料的实验组刺参平均体重随实验时间呈上升趋势,实验结束时,添加20%甘薯块根粉组终末体重显著高于对照组(P0.05),10%、30%组特定生长率(SGR)与对照组差异不显著(P0.05);投喂添加10%甘薯茎蔓粉的实验组刺参SGR与对照组差异不显著(P0.05),其余各组SGR均低于对照组(P0.05)。投喂添加10%、20%甘薯块根粉饲料的实验组刺参体腔液中过氧化氢酶(CAT)、酸性磷酸酶(ACP)、碱性磷酸酶(AKP)均显著高于对照组(P0.05);投喂添加10%甘薯茎蔓粉饲料的实验组ACP显著高于对照组(P0.05),刺参体腔液中的溶菌酶(LZM)、总超氧化物歧化酶(T-SOD)、CAT和AKP与对照组差异不显著(P0.05)。研究表明,当甘薯块根与茎蔓的添加比例分别在30%和20%以下时,可满足刺参的营养需求,促进或保证刺参的生长,提高刺参免疫能力。     

Feed processing affected the digestibility of carbohydrate sources for dourado Salminus brasiliensis

Carbohydrate utilization by fish varies with feeding habits and feed processing. Extruded aquafeeds have increased digestibility of carbohydrate sources resulting from the cooking and gelatinization of this nutrient, making it readily available for all aquatic species. This study aimed at determining the effects of extrusion cooking of feeds in the digestibility of different dietary carbohydrate sources for dourado. Isonitrogenous and isoenergetic diets (530 g kg^?1 crude protein and 20.80 MJ kg^?1 gross energy) containing either corn, toasted cassava flour, wheat flour, broken rice, cassava starch, or corn starch, in extruded or pelletized form and added of chromic oxide as inert marker, were fed to groups of juvenile dourado (73.97 ± 12.0 g; n = 40) stocked in 500‐L polyethylene tanks. Extrusion cooking improved the digestibility of energy and/or starch of corn, cassava starch, wheat flour, rice and corn starch (P < 0.05), but did not affect digestibility of toasted cassava flour (P > 0.05). It is thus fair to infer that dourado, despite being a carnivorous species, is properly fit to digest wheat flour, rice and corn starch in natural form.     

吉富罗非鱼对饲料中维生素B1的需要量

采用维生素B1(VB1)含量为0.08(对照组)、0.57、1.13、2.09、4.11和8.09 mg/kg的6种纯化饲料,分别饲养初始体质量为(64.4±1.5)g的吉富罗非鱼12周,研究VB1对其生长性能、部分血清生化指标、肝脏VB1蓄积量及转酮醇酶基因表达量的影响,以确定其对饲料VB1的需要量.结果显示,随着饲料中VB1含量增加,吉富罗非鱼增重率先呈线性增加后趋于稳定,当饲料中VB1含量为1.13、2.09、4.11、8.09 mg/kg时增重率达最大.吉富罗非鱼肝脏VB1含量随着饲料VB1含量增加不断增大,当增加到2.09 mg/kg后趋于稳定.饲料中缺乏VB1显著提高血清丙酮酸含量(P＜0.05),但对全鱼水分、粗脂肪、粗蛋白、灰分无显著性影响(P＞0.05).饲料中添加VB1显著提高血清高密度脂蛋白胆固醇和肝脏转酮醇酶基因表达量(P＜0.05).饲料中VB1含量大于1.13 mg/kg各组的肝脏转酮醇酶活性显著高于VB1含量小于0.57 mg/kg组(P＜0.05).折线回归分析表明,吉富罗非鱼(64 ～325 g)获得最佳生长时对饲料VB1需要量为1.16 mg/kg;肝脏VB1蓄积量达到最大时,对VB1的需要量为2.06mg/kg.     

吉富罗非鱼对饲料中泛酸的需要量

选用初始体质量为(79.4±1.6)g吉富罗非鱼270尾,随机分成6组(每组3重复,每重复15尾),养殖于500 L养殖桶中,分别饲喂泛酸含量为0.5、4.8、9.5、18.2、36.3和74.4 mg/kg纯化饲料12周,研究确定其对泛酸的需要量。结果表明,随着饲料泛酸含量增加,吉富罗非鱼增重率、肝脏和肌肉泛酸含量均呈先线性增加后稳定的趋势;肥满度和肝体比呈先增加后降低的趋势,均以4.8 mg/kg组最高。全鱼水分含量先降低后增加,全鱼脂肪含量呈现与水分含量相反的趋势。肝总脂含量显著降低,添加组显著低于未添加组(P0.05)。血清高密度脂蛋白含量随着饲料泛酸含量的增加而显著增加(P0.05)。折线回归分析结果表明,吉富罗非鱼(80~350 g)获得最佳生长时对饲料泛酸需要量为10.5 mg/kg,饲料中12.6和13.5mg/kg泛酸可以分别使肝脏和肌肉泛酸累积量达到最大。     

不同糖源对拟穴青蟹仔蟹的生长、体成分及消化酶的影响

在水温26~30℃,盐度18~22条件下,初始体质量(0.012±0.000)g的拟穴青蟹仔蟹饲养在底铺1~2 cm细沙、边缘放5 cm^2瓦片的塑料水桶(直径20 cm,水深20 cm)中,投喂以葡萄糖、蔗糖、糊精、木薯淀粉、玉米淀粉、糊化木薯淀粉和糊化玉米淀粉为糖源的7种等氮等能饲料,养殖3周,研究不同糖源对拟穴青蟹仔蟹生长、体组成及消化酶活性的影响。试验结果显示,不同糖源显著影响拟穴青蟹仔蟹的生长性能(P<0.05);质量增加率和特定生长率依次为糊化木薯淀粉>糊化玉米淀粉>木薯淀粉>玉米淀粉>糊精>蔗糖>葡萄糖;葡萄糖试验组的成活率显著低于其他各组(P<0.05)。不同糖源对拟穴青蟹仔蟹体组成中粗蛋白和粗脂肪含量影响显著(P<0.05),对仔蟹的水分和灰分含量影响不显著(P>0.05);不同糖源对3种消化酶活性影响显著(P<0.05)。拟穴青蟹仔蟹对大分子糖源的生物利用度要大于小分子糖源。在本试验的研究条件下,7种常见糖源中糊化木薯淀粉是拟穴青蟹仔蟹的最适糖源。     

The autochthonous microbiota of the freshwater omnivores jundiá (Rhamdia quelen) and tilapia (Oreochromis niloticus) and the effect of dietary carbohydrates

Previous studies have shown that the gut microbiota of fish differs depending on host feeding habits and these populations may also be influenced by dietary ingredients. In this study, the bacterial populations of the intestinal tract of the opportunistic omnivore jundiá Rhamdia quelen and the typical omnivore tilapia Oreochromis niloticus were investigated in two experiments. In experiment I, the levels of amylolytic, cellulolytic, lipolytic, proteolytic and total culturable bacteria were compared in the proximal, mid and distal intestine using selective agar. Higher levels of amylolytic, cellulolytic, lipolytic, proteolytic and total culturable bacteria were observed in the tilapia than jundiá, in all intestinal regions. Jundiá contained higher levels of proteolytic bacteria and lipid digesting bacteria in the distal intestinal portion as compared with the mid intestine; both fish species also presented more amylolytic bacteria in the distal intestine. In experiment II, the amylolytic intestinal microbiota between the two species was compared after administration of diets containing different carbohydrate sources. Jundiá fed broken rice presented higher total culturable bacterial levels; however, dietary cassava bagasse and ground corn significantly elevated the population of amylolytic bacteria in tilapia (P > 0.05). PCR‐DGGE was also used to assess the bacterial communities in experiment II. A Cetobacterium spp. was detected in jundiá fed diets containing broken rice, and tilapia fed cassava bagasse, dextrin, broken rice and ground corn. Microbial differentiation was further demonstrated between jundiá and tilapia, because an uncultured bacterium was unique in tilapia and an uncultured spirochete was observed only in jundiá; the presence of these bacterial species was also influenced by dietary carbohydrate sources.     

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%。     

不同糖源对卵形鲳鲹(Trachinotus ovatus)日增重、饲料利用和消化酶活性的影响

以葡萄糖、蔗糖、糊精、玉米淀粉和糊化玉米淀粉为糖源制成5种等氮等脂饲料,投喂卵形鲳碜(Trachinotus ovatus)8周,研究不同糖源对其日增重、饲料利用和肝脏消化酶活性的影响.结果显示,不同糖源对卵形鲳鲹日增重、饲料效率和蛋白效率均有显著影响(P＜0.05).糊化玉米淀粉组的日增重、饲料效率和蛋白效率均最高,显著高于非淀粉糖源组(P＜0.05),而与玉米淀粉组无显著差异(P＞0.05);葡萄糖组的日增重、饲料效率和蛋白效率均最低,显著低于其他糖源组(P＜0.05).消化酶活性结果显示,饲料中的不同糖源对卵形鲳鲹的肝脏消化酶活性有显著影响(P＜0.05).两个淀粉组的蛋白酶活性显著低于分子量较低其他三组(P＜0.05);蔗糖组的淀粉酶活性最高,显著高于除糊精组外的其他糖源组(P＜0.05);脂肪酶活性随着糖分子量的增大而增大.本研究中淀粉类大分子糖类对卵形鲳鲹的促生长效果优于葡萄糖、蔗糖和糊精,糊化玉米淀粉组的促生长效果最好.     

Growth and survival rate of three genetic groups fed 28% and 34% protein diets

The strain by nutrition interaction in body weight and survival rate was examined by testing three genetic groups (Selection and Control lines of the GIFT strain, and Red tilapia) at two levels of protein in the diet (28% and 34%). The GIFT strain of Nile tilapia (Oreochromis niloticus) has been selected for high‐breeding values for body weight, whereas the Control was contemporaneously maintained and selected for breeding values of body weight close to the population mean. The Red tilapia (Oreochromis spp) was unselected at the time of the experiment. There were a total of 6000 fish at stocking in the study (2000 fish per genetic group). During the grow‐out period of 147 days, within each genetic group, the fish were randomly assigned to either a 28% or a 34% protein diet. Survival rate during grow‐out averaged 72%. A total of 4335 fish were harvested, with individual body measurements and survival recorded. The effect of genetic group accounted for the largest proportion of variation in body weight and survival, followed by sex and protein level. Across the two dietary protein levels, the GIFT strain had the highest growth. The difference in body weight between the Control and Red tilapia was not statistically significant (P > 0.05). Responses in growth to dietary protein levels also differed between genetic groups. No differences (P > 0.05) in body weight were found in the GIFT selection and Control fish fed 28% or 34% protein diets. However, body weight of Red tilapia was greater in the high‐ than in the low‐protein diet. In contrast to body weight, survival rate from stocking to harvest was affected by protein level. The high‐protein diet significantly improved survival rate, averaging 24% across the three strains. The overall results indicate significant effects of genetic group and dietary protein level on both body weight and survival rate; however, the interaction between strain and dietary protein levels was small and possibly unimportant for these traits. It is concluded that the 28% protein diet used in the selection programme for the GIFT strain results in the selection of genotypes that can perform well under commercial feeds.     

Utilization of different carbohydrate sources and starch forms by bagrid catfish (Mystus nemurus) (Cuv & Val)

Two experiments were conducted to ascertain the utilization of different carbohydrate sources and different forms of starch present in bagrid catfish (Mystus nemurus) fry. The nutritional quality and starch forms of cornstarch, dextrin, broken rice, and sago flour were evaluated in a 4 × 2 factorial design. All diets were formulated to be isonitrogenous (400 g kg^?1 crude protein) and isolipidic (150 g kg^?1 crude lipid), fed to triplicate groups of bagrid catfish fry (initial weight 6.04 ± 0.04 g). Growth studies, enzymatic response and postprandial plasma glucose were observed. A two‐way anova (P > 0.05) analysis of the data obtained showed that the final body weight, specific growth rate (SGR) and food conversion ratio (FCR) were significantly affected by carbohydrate source, but not significantly affected by starch form. Fish fed broken rice and corn starch had similar SGR and FCR compared to fish fed with dextrin and sago flour. The postprandial plasma glucose trend in fish fed with corn starch and broken rice showed a gradual increase while sago flour and dextrin‐fed fish peaked at 2 and 3 h, respectively. Lipogenic enzyme (G6PDH) activity were more pronounced than gluconeogenic enzyme (ME) in M. nemurus irrespective of carbohydrate source and starch form. Therefore, we suggest that raw broken rice and corn starch are suitable carbohydrate sources in the M. nemurus diet.     

Dietary Niacin Requirement of GIFT Tilapia,Oreochromis niloticus,Reared in Freshwater

The aim of our experiment was to determine the dietary niacin requirement of genetically improved farmed tilapia (GIFT) tilapia, Oreochromis niloticus, reared in freshwater. Six semi‐purified diets were formulated to contain graded levels of niacin (6.4 [basal diet], 16.8, 36.8, 68.5, 143.8, and 297.8 mg/kg). Each diet was fed to triplicate groups of 30 fish (initial average weight 87.2 ± 3.3 g) for 12 wk in 5.6‐m³ aquaria (r = 1.5 m, h = 0.8 m). Results showed that the weight gain rate (WGR) of the fish increased linearly with dietary niacin levels increasing, but there were no further benefits above 36.8 mg/kg. The niacin concentrations in fish livers were positively correlated with dietary levels of niacin and plateaued when niacin in diet exceeded 84.6 mg/kg. With increasing dietary niacin level, serum high density lipoprotein cholesterol (HDLC) content significantly increased, while serum triacylglycerol (TG) content significantly decreased (P < 0.05). There were no significant differences in serum glucose (GLU) and total cholesterol (T‐CHO) contents in the separate fish groups (P > 0.05). Broken‐line regression analysis showed that GIFT tilapia (87–376 g) require a minimum of 20.4 mg/kg niacin in the diet for maximal growth, and 84.6 mg/kg for the highest liver niacin accumulation.