饲料中不同脂肪源对草鱼生长及其肌肉和肝脏脂肪含量的影响

饲料中不同脂肪源对草鱼生长及其肌肉和肝脏脂肪含量的影响成永旭，王联合，陈居明（河南师范大学生物系，４５３２００）脂肪在鱼类营养中除作为能源物质外，对机体的生长、发育和繁殖等亦有重要影响，因此，饲料中脂肪含量或脂肪质量都可能影响鱼的生长。本试验在饲料中...     

饲料中脂肪含量对草鱼生长的影响

<正> 近年来,从能量研究查明,鱼类对蛋白质的要求量随饲料中可消化能量含量多寡而异(荻野,1976)。提高饲料中可消化能量,可以降低饲料蛋白质作为能量的消费,使蛋白质利用率提高,两者同存在一个最适     

微藻粉替代鱼油对星斑川鲽幼鱼生长、体组成和生理指标的影响

为探讨微藻粉替代鱼油对星斑川鲽(Platichthys stellatus,Pallas 1788)幼鱼生长、体组成和生理指标的影响,以鱼油为主要脂肪源配制基础饲料(FO),分别用裂壶藻粉(SO)、微绿球藻粉(NO)及两种藻粉的混合物(MO)替代鱼油中的DHA、EPA,不足部分用玉米油补齐,制成4种等氮等能的实验饲料,投喂星斑川鲽幼鱼(初始体重7.35 g±0.03 g)90 d。结果显示,与FO组相比,SO组的生长性能无显著差异(P0.05),NO组和MO组特定生长率、蛋白质效率和脏体比显著降低(P0.05),饲料系数显著增大(P0.05);MO组的全鱼粗蛋白含量显著高于其他组(P0.05),FO组与MO组的全鱼粗脂肪含量显著高于其他组(P0.05),FO组背肌粗灰分含量显著低于其他组(P0.05);藻粉替代鱼油对肌肉和肝脏脂肪酸组分影响显著,肌肉的C16:0和DHA含量与其在饲料中所占的百分比呈显著正相关(r=0.973,0.967,P0.05),C14:0和C16:1n-7呈极显著正相关(r=1.00,0.996,P0.01),肝的C18:2n-6、n-6 PUFA和DHA/EPA呈显著正相关(r=0.983,0.976,0.977,P0.05),C16:1n-7呈现极显著正相关(r=0.992,P0.01);NO组和MO组血清谷丙转氨酶(ALT)、甘油三酯(TG)、胆固醇(CHO)和碱性磷酸酶(ALP)的含量较FO组显著降低(P0.05),NO组血清谷草转氨酶(AST)和葡萄糖(GLU)含量显著低于其他组(P0.05)。研究表明,本实验条件下裂壶藻粉可以替代星斑川鲽幼鱼饲料中的鱼油而不对其生长和生理指标产生负面影响,并且在一定程度上能提高星斑川鲽的营养价值。     

饲料中添加谷胱甘肽对草鱼生长、生理指标和抗病力的影响

选用初始体质量约8.50 g的草鱼(Ctenopharyngodon idella),在56 d的饲养期中分别投喂添加5种不同剂量谷胱甘肽(GSH)(添加量分别为0 mg/kg、100 mg/kg、200 mg/kg、300 mg/kg和400 mg/kg)的试验饲料,观察GSH对草鱼生长、生理指标和抗病力的影响。结果表明,饲料中添加GSH能够提高草鱼特定生长率、存活率和饲料效率。其中,300 mg/kg GSH组草鱼的特定生长率和400 mg/kg GSH组草鱼的存活率显著高于对照组;添加GSH各组草鱼的饲料效率均显著高于对照组,当添加量为200 mg/kg时草鱼饲料效率达到最高。与对照组相比,饲料中添加GSH的各组草鱼肝胰指数明显升高,其中200 mg/kg组达到显著水平。饲料中添加GSH能够提高血清IGF-1水平,其中300 mg/kg和400 mg/kg组显著高于对照组。与对照组相比,各实验组草鱼血液白细胞数目有不同程度升高,其中300 mg/kg和400 mg/kg组均达到显著水平。饲料中添加GSH可以提高草鱼对嗜水气单胞菌的抵抗能力,其中200 mg/kg GSH组草鱼攻毒后存活率达到最高。以特定生长率为判定指标,GSH在草鱼饲料中的适宜添加量为350 mg/kg。     

日粮中鱼蛋白水解物对黄颡鱼生长、体成分和血清生理指标的影响

为了探讨鱼蛋白水解物对黄颡鱼生产性能的影响,以日本鳀粉为对照,以实用型黄颡鱼饲料配方模式为基础开展实验:1以30.5%鱼粉为对照(FM),在相同配方模式下,以6%鱼蛋白水解物(MPH6)替代20%的鱼粉;2以30.5%鱼粉为对照(FM),在无鱼粉日粮中分别添加3%(FPH3)、6%(FPH6)、12%(FPH12)鱼蛋白水解物;共设计5组等氮等能实验日粮,在池塘网箱中养殖黄颡鱼[初始体质量(30.08±0.35)g]60 d。结果显示:与FM相比,FPH12在SGR、FCR、PRR和FRR方面均无显著差异,而MPH6、FPH3、FPH6组SGR降低了15.45%~24.39%,FCR升高了32.14%~42.86%,MPH6、FPH6差异显著,在PRR和FRR方面,MPH6、FPH3、FPH6组PRR降低了21.11%~27.78%,MPH6组FRR降低了41.51%;全鱼水分、粗蛋白、粗脂肪和灰分各组间差异不显著,FPH3、FPH6、FPH12肌肉多种游离氨基酸水平显著高于FM,其中Thr、Val、His与其在日粮中的水平显著相关;FPH6组HSI显著低于FM,鱼蛋白水解物对CP、VSI、肠体比的影响不显著;血清AST、ALT、HDL、LDL、TP、CHOL、TG无显著差异,FPH3组ALB显著低于FM。研究表明:黄颡鱼日粮中,12%鱼蛋白水解物(干物质)与30.5%鱼粉在生长速度、饲料效率、血清生理指标等方面具有一定的等效性;过高的植物蛋白日粮影响了黄颡鱼的生产性能;饲喂鱼蛋白水解物日粮使黄颡鱼肌肉游离氨基酸的含量升高,特别是呈味氨基酸的含量增加。     

日粮铁对草鱼生长、营养成分和部分血液指标的影响

选用(7.12±0.22)g的草鱼(Cenopharyngodon idellus)鱼种,分别在纯化日粮中添加铁0,100,200,300,400,500 mg/kg,进行为期78 d的生长试验以考察铁对草鱼生长性能、营养成分和部分血液指标的影响。试验结果显示,日粮中添加铁对草鱼的生长、体成分和血红蛋白和红血细胞数目等都有显著影响。日粮中添加铁300 mg/kg时,草鱼增重率、特定生长率、饲料效率、蛋白质效率比、蛋白沉积效率达最大值;体蛋白和肌肉蛋白含量高,脂肪含量低,灰分含量高;血红蛋白和红血细胞均达最高水平。结果说明:草鱼纯化日粮中铁的适宜添加量为300 mg/kg。     

饲料中添加丁酸钠对草鱼生长、消化酶活性、血清生化指标和肠道组织学的影响

为了探究饲料中补充不同水平丁酸钠对草鱼生长性能、肠道消化酶活性、血清生化指标和肠道组织形态的影响,分别添加0 mg/kg (SB0)、1 000 mg/kg (SB1)、2 000 mg/kg(SB2)和3 000 mg/kg (SB3)的微囊丁酸钠(含50%丁酸钠)至基础饲料中,设计4组等氮等脂的实验饲料。选取300尾体质健康的草鱼(10.0±0.1) g,分成4组,每组3个重复,每个重复25尾鱼,放置在水泥池中养殖8周。结果显示,各组草鱼增重率为273.7%～279.9%,饲料系数为1.55～1.60,饲料中补充丁酸钠对草鱼生长性能和体成分无显著影响。与对照组相比,添加不同水平的丁酸钠均显著提高了肠道蛋白酶活性和血清超氧化物歧化酶(SOD)活性,降低了血清谷草转氨酶(AST)活性,SB1组血清碱性磷酸酶(AKP)活性显著升高,而SB2和SB3组血清谷丙转氨酶(ALT)活性显著降低。各组肠道淀粉酶活性、血清酸性磷酸酶(ACP)、甘油三酯(TG)、葡萄糖(GLU)、总蛋白(TP)和D-乳酸(D-LA)无显著差异。在肠道组织学方面,各丁酸钠补充组肠道绒毛高度和SB1、SB2组肌层厚度显著...     

饲料中添加生物素对草鱼幼鱼生长、体成分和血清生化指标的影响

在纯化饲料中分别添加生物素0、0.05、0.10、0.20、0.40、0.80、1.60 mg/kg投喂初始质量为(5.92±0.25)g的草鱼(Ctenopharyngodon idellus)幼鱼8周,研究了不同生物素添加量对草鱼幼鱼生长性能、饲料系数、机体营养成分、血清生化指标的影响。试验结果显示:与对照组相比,添加生物素提高了草鱼幼鱼的增重率、特定生长率,降低了饲料系数。添加量为0.40 mg/kg时草鱼幼鱼的特定生长率和增重率最大,饲料系数最低,并与对照组存在显著差异(P<0.05);添加不同水平生物素对草鱼幼鱼全鱼水分、粗蛋白、粗脂肪含量无显著影响,但添加量为0.40 mg/kg时粗蛋白含量最大。0.10 mg/kg组和0.20 mg/kg组的全鱼灰分含量显著高于对照组(P<0.05);添加生物素对血清总蛋白(TP)、血糖(GLU)和总胆固醇(TC)无显著影响,但显著提高了血清甘油三酯(TG)含量,各添加组TG含量均显著高于对照组(P<0.05),1.60 mg/kg添加组的高密度脂蛋白胆固醇(HDL-C)和低密度脂蛋白胆固醇(LDL-C)含量显著高于对照组(P<0.05)。综合本试验结果,草鱼幼鱼饲料中生物素适宜添加量为0.40 mg/kg。     

实用饲料补充结晶或包膜赖氨酸对草鱼生长、血清游离氨基酸和肌肉蛋白质合成率的影响

研究设计 4种试验饲料 (纯化饲料、实用饲料以及分别补充结晶和包膜赖氨酸的两种实用饲料 )。试验草鱼放养在玻璃钢水族箱 (10 0cm× 5 0cm× 5 0cm)中 ,每箱放养 30尾 (平均体重 7.2 7± 0 .5g) ,每种处理设 3个平行组 ,饲养 9周。试验结果表明 ,纯化饲料组的增重率和蛋白质合成率 (Ks)明显高于 3组实用饲料 (P <0 .0 5 )。实用饲料补充包膜赖氨酸与不补充或补充结晶赖氨酸比较 ,增重率、蛋白质效率、血清必需氨基酸平衡指数(EAAP)和蛋白质合成率都得到改善。包膜赖氨酸 ,是补充饲料蛋白质的一种很好的途径。     

饲料中添加氧化鱼油对黑鲷幼鱼生长的影响

研究了饲料中添加氧化鱼油对黑鲷（Acanthopagrus schlegeli）生长性能、脂质过氧化及肝组织结构的影响。分别以新鲜鱼油（过氧化物值POV，1．27meq O2·kg^-1油）与氧化酸败鱼油（POV，45meq O2·kg^-油）为脂肪源配制等蛋等能的两种配合饲料，投喂平均体重18．9g的黑鲷幼鱼9周。结果显示，氧化鱼油显著降低了黑鲷幼鱼的增重率（WG）、饲料效率（FE）及蛋白质效率（PER）（P〈0．05）。饲料中添加氧化鱼油导致鱼体蛋白质含量极显著降低（P〈0．01）、肝脏与肌肉中脂肪含量显著升高（P〈0．05），而对鱼体、肝脏及肌肉中的水分及灰分含量无显著影响（P〉0．05）。氧化鱼油组肝脏中脂质过氧化产物丙二醛（MDA）含量显著高于对照组，而维生素E含量则显著低于对照组（P〈0．05）。饲料中添加氧化鱼油显著影响黑鲷肝脏内主要抗氧化酶活性，氧化鱼油组肝脏中超氧化物歧化酶（SOD）与过氧化氢酶（CAT）活性显著高于对照组（P〈0．05）；组织学结果显示氧化鱼油组肝脏出现明显病变，细胞核多集中在肝细胞边缘，肝细胞变大。统计分析表明，氧化酸败油脂显著降低了黑鲷的生长性能，加重了组织中脂质过氧化的程度，并导致肝脏组织发生病变。     

Effects of lysine and methionine supplementation on growth,body composition and digestive function of grass carp (Ctenopharyngodon idella) fed plant protein diets using high‐level canola meal

A 76‐day feeding trial was carried out to evaluate the effects of Lysine and Methionine supplementation on growth and digestive capacity of grass carp (Ctenopharyngodon idella) fed plant protein diets using high‐level canola meal (CM). Fish with initial average weight 103.9 ± 0.6 g were fed three extruded diets. Fish meal (FM) diet was formulated as the normal control with 40 g kg^?1 FM and 300 g kg^?1 CM; CM diet was prepared by replacing all FM with CM (total 340 g kg^?1) without Lys or Met supplementation; CM supplement (CMS) diet was similar to CM diet but was supplemented with essential amino acids (EAA) to ensure the levels of Lys and Met similar to those in the FM diet. Feed intake, feed efficiency and specific growth rate of the grass carp fed CMS and FM diets were similar (P > 0.05), but higher than those of the grass carp fed CM diet (P < 0.05). The hepatosomatic index, relative gut length, intestosomatic index and intestinal folds height were significantly improved in fish fed FM and CMS diets as compared to CM diet (P < 0.05). Lower activities of trypsin, lipase and amylase in hepatopancreas were observed in fish fed CM diet (P < 0.05). Three hundred and forty gram per kilogram CM without Lys or Met supplementation significantly decreased trypsin, lipase and amylase mRNA levels in hepatopancreas (P < 0.05). These results indicated that the high supply of CM (340 g kg^?1) in plant protein (200 g kg^?1 soybean meal and 100 g kg^?1 cottonseed meal) diets decreased digestive ability through decreasing digestive enzyme activities and enzyme gene's expressions of grass carp, and these side effects can be reversed by supplementing Lys and Met. Therefore, CM could be high level used in a plant protein blend‐based extruded diet for grass carp as long as EAA were supplemented.     

饲料氧化鱼油引起草鱼肠道黏膜结构屏障损伤

为了研究饲料氧化鱼油对草鱼肠道屏障结构和肠道通透性的影响。(实验目的)以豆油、鱼油、氧化鱼油作为饲料脂肪源,分别设计鱼油组(6F)、豆油组(6S)、2%氧化鱼油(2OF)、4%氧化鱼油(4OF)及6%氧化鱼油(6OF)5组等氮、等能半纯化饲料,在池塘网箱养殖草鱼(平均体重74.8士1.2)72d。采用实时荧光定量PCR(qRT-PCR)的方法,测定了草鱼肠道紧密连接蛋白中闭锁蛋白Occludin,闭合蛋白Claudin3、Claudin15a和胞浆蛋白ZO-1、ZO-2、ZO-3的基因表达活性,并结合肠黏膜细胞间紧密连接结构透射电镜观察结果、肠道通透性标志性指标测定结果综合分析。(实验方法)结果显示：在添加氧化鱼油后,(1)血清二胺氧化酶活性、内毒素和D-乳酸含量都出现显著增加(P<0.05);(2)组成肠黏膜细胞间紧密连接结构的闭合蛋白Claudin-3、Claudin-15a和胞浆蛋白ZO-1、ZO-2、ZO-3基因表达活性显著下调(P<0.05),而闭锁蛋白Occludin基因表达活性出现不同程度的下调,但差异不显著(P>0.05);(3)透射电镜观察结果显示肠黏膜细胞间紧密连接结构出现缝隙;⑷饲料中的AV值、POV值、MDA含量与闭合蛋白Claudin-3、Claudin-15a,胞浆蛋白ZO-1、ZO-2、ZO-3和闭锁蛋白Occludin基因表达活性均显示负相关关系的变化趋势,其中饲料POV值、MDA含量与胞浆蛋白ZO-1基因表达活性呈极显著负相关关系(P<0.05)。(实验结果)结果表明,在饲料中添加氧化鱼油后,氧化鱼油中的过氧化物、丙二醛等油脂氧化产物导致组成肠道黏膜细胞间紧密连接结构的蛋白基因表达活性显著下调、紧密连接物理性结构显著损伤,致使肠黏膜屏障结构的完整性被破坏、肠黏膜通透性显著增加。(实验结论)     

不同脂肪源饲料对草鱼稚鱼生长的影响

不同脂肪源饲料对草鱼稚鱼生长的影响刘玮，徐萍，任本根，龚纲明（江西省科学院生物资源研究所，南昌３３００２９）关键词草鱼，鱼饲料，必采脂肪酸ＥＦＦＥＣＴＳＯＦＤＩＥＴＳＣＯＮＴＡＩＮＩＮＧＤＩＦＦＥＲＥＮＴＬＩＰＩＤＳＯＮＧＲＯＷＴＨＯＦＪＵＶＥＮＩＬ...     

Effects of dietary chlorogenic acid on growth,flesh quality and serum biochemical indices of grass carp (Ctenopharyngodon idella)

The study was to investigate effects of dietary chlorogenic acid (CGA) on growth performance, flesh quality and serum biochemical indices of grass carp (95.1 ± 0.3 g) (Ctenopharyngodon idella) fed seven different diets, including control diet, Eucommia ulmoides (EU)‐supplemented diet (20 g kg^–1) and CGA‐supplemented diets containing 100, 200, 400, 600 and 800 mg/kg CGA. Contents of collagen and alkaline‐insoluble collagen in muscle and skin were significantly increased by dietary CGA and EU (p < .05). Total essential amino acids (TEAA) and total amino acids (TAA) in muscle of grass carp fed EU diet or 400, 600 and 800 mg/kg CGA diet were significantly higher than those of fish fed control diet and 100 and 200 mg/kg CGA diet (p < .05). Fish fed 200–800 mg/kg CGA showed significantly lower muscle crude lipid content than EU, control and 100 mg/kg CGA groups (p < .05). Fish fed CGA‐supplemented diets (100–800 mg/kg) had significantly higher muscle fibre density and lower muscle fibre diameter than control group (p < .05). In conclusion, supplementation of CGA improved flesh quality of grass carp, and supplemental level of CGA for improving flesh quality and growth was estimated to be 400 mg/kg diet.     

豆粕替代鱼粉对青鱼幼鱼生长及生理生化指标的影响

以初始体重(5.90±0.01)g的青鱼(Mylopharyngodon piceus)为研究对象,用豆粕替代不同水平鱼粉,配制5种等氮等能的实验饲料,分别为30%鱼粉(对照组)、25%鱼粉、20%鱼粉、15%鱼粉和15%鱼粉+晶体氨基酸,试验持续8周。结果显示:当鱼粉含量为15%时,其增重率、特定生长率、肌肉鲜味氨基酸含量和总氨基酸含量显著低于对照组,而饲料系数则显著高于对照组,添加晶体氨基酸对青鱼生长无显著改善;各处理组间甘油三酯(TG)、总蛋白(TP)、总胆固醇(TC)含量及谷丙转氨酶(ALT)活性无显著差异,但15%鱼粉组和15%鱼粉+晶体氨基酸组的青鱼的血糖含量和谷丙转氨酶活性显著高于对照组。结果表明,青鱼幼鱼实用饲料中鱼粉含量以不低于20%为宜,添加晶体氨基酸对青鱼幼鱼的生长无改善作用。     

Effects of total replacement of fish oil by pork lard or rapeseed oil and recovery by a fish oil finishing diet on growth,health and fish quality of gibel carp (Carassius auratus gibelio)

An 84‐day growth trial was designed to investigate effects of dietary replacements fish oil with pork lard (PL) or rapeseed oil (RO) on growth and quality of gibel carp (Carassius auratus gibelio var. CAS III) (initial body weight: 158.2 ± 0.2 g), and responses of the fish refed fish oil (FO) diet. Three isonitrogenous (crude protein: 30%) and isolipid (crude lipid: 10%) diets were formulated containing 7.73% FO, PL or RO. Five experimental treatments including FO group (FO), PL group (PL), RO group (RO), group fed PL for 42 days and refed FO for 42 days (PL+rFO), RO and refed FO group (RO+rFO) was tested. At the end of first 42 days, the fish fed PL and RO had higher mortality than that of the control (P > 0.05). At the end of whole experiment, fish fed PL and RO showed higher plasma cortisol than FO fish (P < 0.05). RO+rFO fish showed higher lysozyme activity than RO fish (P < 0.05). Fish growth and feed utilization, composition of whole body and muscle, free amino acids, texture, off‐flavour substances or sensory attributes were not affected by dietary treatments (P > 0.05). PL and RO diet decreased muscle EPA, DHA and n‐3/n‐6 ratio (P < 0.05), while FO‐refeeding had recovery effect. It can be concluded that the replacement of FO by PL and RO does not affect the growth, feed utilization or fish tasting quality in gibel carp. Fish muscle fatty acids modified by dietary PL and RO can be recovered by refeeding with FO diet.     

饲料中补充晶体或微囊赖氨酸对草鱼生长和血浆总游离氨基酸的影响

为考察饲料中补充晶体或微囊赖氨酸对草鱼生长性能的影响,配制了豆粕含量为23%(高豆粕组),15%(低豆粕组)的两种实用饲料,在低豆粕饲料中补充晶体赖氨酸或微囊赖氨酸,使赖氨酸达到与高豆粕组一致的水平,共4个处理组,即高豆粕组、低豆粕组、低豆粕+晶体赖氨酸(晶体赖氨酸组)、低豆粕+微囊赖氨酸(微囊赖氨酸组),每处理设3个平行。饲养平均体重为(49.0±2.0)g的草鱼8周。结果表明,各组鱼体增重率分别为279.3%、239.7%、245.6%、277.5%,饲料系数为1.62、1.88、1.85、1.62。与低豆粕组相比,添加晶体赖氨酸对草鱼生长无改善(P>0.05),而添加微囊赖氨酸则提高草鱼增重率15.8%(P<0.05),降低饲料系数0.24(P<0.05),在增重率与饲料系数方面达到与高豆粕组基本一致的水平(P>0.05)。对草鱼摄食上述4种饲料0、1、2、3、4、5h后的血浆总游离氨基酸浓度测定结果表明,添加微囊赖氨酸血浆总游离氨基酸的变化趋势与高豆粕组、低豆粕组一致,即在饲后3h达到高峰,而添加晶体赖氨酸使血浆总游离氨基酸的吸收峰值提前。晶体赖氨酸经微囊化后,其水中溶失率显著降低(P<0.05),仅...     

蝇蛆粉替代鱼粉对黄颡鱼肌肉品质的影响

选用初始体质量约2.02 g的黄颡鱼(Pelteobagrus fulvidraco)960尾,随机分为6组,分别投喂6种用蝇蛆粉替代饲料中0%、20%、40%、60%、80%、100%鱼粉配制的等氮(39.5%)等能(16.8 MJ/kg)饲料,分别记为G0、G20、G40、G60、G80和G100。养殖期为60 d。结果显示,黄颡鱼肌肉水分、粗蛋白质、粗脂肪含量受蝇蛆粉替代鱼粉水平的影响不显著(P>0.05),但G60～G100灰分含量与G0相比显著升高(P<0.05)。蝇蛆粉替代鱼粉对肌肉pH、滴水损失(DL)、蒸煮损失(CL)和超氧化物歧化酶(SOD)活性影响不显著(P>0.05)。与G0相比,G20～G100肌肉胶原蛋白含量差异不显著(P>0.05),G40～G60肌肉丙二醛(MDA)含量显著降低(P<0.05)。与G0相比,G80肌肉精氨酸(Arg)、组氨酸(His)、苯丙氨酸(Phe)、必需氨基酸(TEAA)含量显著高(P<0.05),各替代组总氨基酸含量差异不显著(P>0.05)。各组肌肉谷氨酸(Glu)、甘氨酸(Gly)、丙氨酸(Ala)、天冬氨酸(Asp)等风味氨基酸和总风味氨基酸(TFAA)含量差异不显著(P>0.05)。肌肉C14:0、C18:3n-3、DHA、EPA+DHA、多不饱和脂肪酸(PUFA)、n-3 PUFA含量和n-3/n-6比值随蝇蛆粉替代鱼粉水平的升高而降低,其中G60～G100显著低于G0(P<0.05);C16:1、单不饱和脂肪酸(MUFA)含量随替代水平增加而升高,其中G60和G100显著升高(P<0.05)。结果表明,当蝇蛆粉替代鱼粉水平不超过40%时,除MDA含量显著降低外,蝇蛆粉对黄颡鱼肌肉常规成分、理化指标、氨基酸和脂肪酸含量影响不显著。     

Response of gibel carp (Carassius auratus gibelio) to increasing levels of dietary lysine in zero fish meal diets

To investigate the response of gibel carp to dietary lysine levels in zero fish meal (FM) diets, 8 experimental diets were designed. Among them, diet 1 and diet 2 with 150 g/kg FM, methionine, lysine and threonine were supplemented in diet 2. Diet 3 was without FM but matched the amino acid profile of diet 2 except for lysine. Diets 4–8 were based on diet 3, with graded levels of lysine. After 8‐week feeding trail, final body weight, weight gain (WG), specific growth rate, feed conversion ratio (FCR) and feed intake were significantly improved by diets 1–2 and 6–8 compared with diet 3. Plasma glucose, triglyceride, immunoglobulin G and aspartate aminotransferase levels in diets 4–8 were higher than those in diet 1. Apparent digestibility coefficients (ADCs) of protein, energy, methionine, lysine, valine, histidine and phenylalanine in diet 1 were significantly lower than those in diet 6. The highest ADC of isoleucine was found in diet 3. TOR, IGF‐1, JAK3, STAT4, STAT6 and PepT2 mRNA levels were significantly increased with increasing dietary lysine up to a certain level in zero FM diet and lower than diets 1–2. Based on WG and FCR, the optimal lysine requirement of juvenile gibel carp was determined to be 24.4 g/kg and 24.2 g/kg (65.9 g/kg and 65.4 g/kg of dietary protein) in zero FM diet, respectively, using quadratic regression analysis.