Dietary l‐methionine requirement of juvenile black sea bream (Sparus macrocephalus) at a constant dietary cystine level

An 8‐week feeding trial was conducted to determine the effects of dietary methionine level on juvenile black sea bream Sparus macrocephalus. Fish (initial body weight: 14.21 ± 0.24 g) were reared in eighteen 350‐L indoors flow‐through circular fibreglass tanks (20 fish per tank). Isoenergetic and isonitrogenous diets contained six levels of L‐methionine ranging from 7.5 to 23.5 g kg⁻¹ of dry diet in 3.0 g kg⁻¹ increments at a constant dietary cystine level of 3.1 g kg⁻¹. Growth performance and feed utilization were significantly influenced by dietary methionine levels (P < 0.05). Maximum weight gain (WG), specific growth rate (SGR), feed efficiency ratio, protein efficiency ratio and protein productive value (PPV) occurred at 17.2 g methionine kg⁻¹ diet, beyond which they showed declining tendency. Protein contents in whole fish body and dorsal muscle were positively correlated with dietary methionine level, while muscle lipid content was negatively correlated with it. Apparent digestibility coefficients (ADCs) of dietary nutrients were significantly affected by dietary treatments except for ADCs of crude lipid. Fish fed the grade level of methionine demonstrated a significant improvement in whole‐body methionine content, total essential amino acids (∑EAA), total non‐essential amino acids (∑NEAAs) and ∑EAA/∑NEAA ratio (P < 0.05). Regarding serum characteristics, significant differences were observed in total cholesterol, glucose and free methionine concentration (P > 0.05), while total protein level and triacylglycerol concentration kept relatively constant among treatments (P < 0.05). Analysis of dose response with second‐order polynomial regression on the basis of either SGR or PPV, the optimum dietary methionine requirements of juvenile black sea bream were estimated to be 17.1 g kg⁻¹ of diet (45.0 g kg⁻¹ methionine of protein) and 17.2 g kg⁻¹ of diet (45.3 g kg⁻¹ methionine of protein) in the presence of 3.1 g kg⁻¹ cystine, respectively.     

Optimum arginine requirement of juvenile black sea bream,Sparus macrocephalus

An 8‐week feeding trial was conducted to determine the dietary arginine requirement of juvenile black sea bream Sparus macrocephalus in 18 350 L indoors flow‐through circular fibreglass tanks. Six isonitrogenous and isoenergetic diets were formulated to contain graded levels of l ‐arginine (1.85%, 2.23%, 2.51%, 2.86%, 3.20% and 3.46% dry diet) from dietary ingredients and crystalline arginine. Each diet was randomly assigned to triplicate groups of 25 juvenile fish (10.51±0.15 g) twice daily (08:00 and 16:00 hours) to apparent satiation. Results showed that the specific growth rate (SGR) increased with increasing dietary arginine levels up to 2.51% and remained nearly the same thereafter. Feed efficiency ratio, protein efficiency ratio (PER) and protein productive value all showed an increasing tendency and then levelled off. Apparent digestibility coefficients of dry matter, crude protein and gross energy significantly improved up to 2.86% arginine diet and decreased at different extents thereafter. Fish fed 1.85% arginine diet had significantly lower protein content in the whole body and dorsal muscle than those fed diets supplemented with or >2.86% of arginine. Lipid content decreased and lower value occurred at 3.46% of dietary arginine. The dietary essential amino acid composition in the whole body of the black sea bream was significantly influenced by dietary arginine. Arginine retention increased with an increasing dietary arginine level from 1.85% to 3.20%, then declined slightly at 3.46% arginine diet. Serum biochemical parameters were significantly affected by the dietary arginine level except for the cholesterol content. Broken‐line regression based on SGR and second‐order polynomial regression based on PER indicated that the optimum dietary arginine requirements for juvenile black sea bream were 2.79% and 3.09% diet, corresponding to 7.74% and 8.13% of the dietary protein respectively.     

Effect of dietary supplemental l‐carnitine on growth performance,body composition and antioxidant status in juvenile black sea bream,Sparus macrocephalus

Effects of dietary l ‐carnitine were studied in juvenile black sea bream (Sparus macrocephalus). The semipurified basal diet [crude protein 450 g kg^?1 dry matter (DM); crude lipid 126 g kg^?1 DM] was formulated to choose white fishmeal as the protein source and fish oil plus corn oil (1 : 1) as the lipid source. Six diets (control + diets 1–5) containing 0.1, 0.12, 0.16, 0.24, 0.39 and 1.1 g of l ‐carnitine kg^?1 diet were fed to triplicate groups of black sea bream (initial weight 13.10 ± 0.05 g) for 8 weeks. At the end of the feeding trial, growth performance, body composition and antioxidant status were determined. The results showed that relative growth rate (RGR) was significantly improved by the elevation of dietary l ‐carnitine level from 0.1 to 0.24 g kg^?1, but decreased with further increment (P < 0.05). Lipid content decreased significantly (P < 0.05) in the dorsal muscle whereas increased (P < 0.05) in the liver with the addition of dietary l ‐carnitine. Dietary l ‐carnitine supplements elevated enzymatic antioxidants (superoxide dismutase, SOD; catalase, CAT; glutathione‐S‐transferase, GST) activities (P < 0.05) yet decreased the content of non‐enzymatic factor, total sulphydryl groups (TSH) (P < 0.05). In summary, the optimum dietary l ‐carnitine level was 0.284 g kg^?1 diet by second‐polynomial regression analysis based on RGR (y = ?647.4x² +367.97x + 234.55; R² = 0.977, x = dietary l ‐carnitine levels, y = RGR), and dietary l ‐carnitine addition within the levels adopted in our study could depress lipid peroxidation in tissues of juvenile black sea bream.     

A study on dietary l‐lysine requirement of juvenile yellow catfish Pelteobagrus fulvidraco

An 8‐week feeding trial was conducted to determine lysine requirement of juvenile yellow catfish (Pelteobagrus fulvidraco) by feeding formulated diets containing crystalline l ‐lysine. Six isonitrogenous and isoenergetic diets (405 g kg^?1 protein, 18 kJ g^?1 gloss energy) containing fish meal together with soybean protein concentrate as protein sources and fish oil together with soybean oil as lipid sources were formulated. Crystalline l ‐lysine was added into the six diets to acquire lysine concentrations of 17.3, 21.8, 26.0, 31.3, 35.5 and 41.9 g kg^?1 dry diets, respectively. Mixture of crystalline amino acid was supplemented to simulate the amino acid profile in muscle of yellow catfish. The results indicated that final body weight (FBW), weight gain (WG), specific growth rate (SGR), feed efficiency (FE) and protein efficiency (PE) increased with the increase in dietary lysine level from 17.3 to 31.3 g kg^?1 of diet and then decreased as the dietary lysine levels further increased. No significant difference in survival rate was found among all the dietary treatments. One‐slope, quadratic broken‐line analysis on the basis of SGR showed that the dietary l ‐lysine requirement of juvenile yellow catfish was 33.1 g kg^?1 of dry diet (83.2 g kg^?1 of dietary protein).     

Dietary l‐lysine requirement of juvenile Chinese sucker,Myxocyprinus asiaticus

An 8‐week feeding trial was conducted to quantify the dietary l ‐lysine requirement of juvenile Chinese sucker with an initial weight of 1.81 ± 0.04 g reared in indoor flow‐through and aerated tanks. Six isonitrogenous and isoenergetic practical diets were formulated to contain graded levels of lysine (1.23%, 1.80%, 2.39%, 2.98%, 3.56% and 4.18% dry matter) at 0.6% increments from dietary ingredients and crystalline l ‐lysine. Each diet was randomly assigned to triplicate groups of 30 fish each and was fed to apparent satiation by hand three times a day (09:00, 13:00 and 17:00 hours) for 8 weeks. There were significant differences in growth performance and feed utilization among the treatments. Weight gain (WG), specific growth rate and protein efficiency ratio (PER) significantly increased with increasing lysine levels up to 2.39% of diet (P < 0.05) and remained nearly the same thereafter (P > 0.05). Feed efficiency was the poorest for fish fed the lowest lysine diet (P < 0.05) and showed no significant differences when dietary lysine level increased from 2.39% to 4.18%. The N retention (% N intake) significantly increased with dietary lysine level but did not attain a plateau (P < 0.05). Survival could not be related to dietary treatments. Whole body protein increased (P < 0.05) and whole body lipid decreased (P < 0.05) with increasing dietary lysine level. The condition factor and hepatosomatic index were significantly affected by dietary lysine levels, however, viscersomatic index, whole body moisture and ash did not differ significantly among dietary treatments. Broken‐line analysis on the basis of WG and PER showed that dietary lysine requirements of juvenile Chinese sucker were 2.43% and 2.40% dry diet (5.52% and 5.45% dietary protein) respectively. Based on the ideal protein approach and the A/E ratios determined from muscle amino acid profile an estimation of the EAA requirements of Chinese sucker juveniles were calculated.     

黑鲷幼鱼饲料蛋白源氨基酸平衡的研究

以黑鲷幼鱼肌肉的氨基酸组成作为幼鱼饲料中必需氨基酸需要量的标准模式,通过必须氨基酸指数（ＥＡＡＩ）和生物饲养试验结果相结合,对黑钱财幼鱼的９种不同蛋白源酸比的饲料进行了比较研究,对黑钱财幼鱼配合饲料中氨基酸平衡和蛋白质营养价值进行了评估,筛选出个高效饲料蛋白源配方;表明ＥＡＡＩ是鱼用饲料蛋白质营养价值评估和氨基酸平衡研究的一种简便有效的评价指标。     

Quantitative l-lysine requirement of juvenile grouper Epinephelus coioides

An 8‐week feeding trial was conducted to determine the quantitative lysine requirement of juvenile grouper Epinephelus coioides (initial mean weight: 15.84 ± 0.23 g, mean ± SD) in eighteen 500‐L indoors flow‐through circular fibreglass tanks provided with sand‐filtered aerated seawater by feeding diets containing six levels of l ‐lysine ranging from 19.2 to 39.5 g kg^?1 dry diet in 4 g kg^?1 increments. The diets, in which 250 g crude protein kg^?1 diet came from fish meal and soybean protein concentrate, and 230 g kg^?1 from crystalline amino acids, were formulated to simulate the amino acid profile of 480 g kg^?1 whole chicken egg protein except for lysine. Each diet was assigned to three tanks in a completely randomized design. Grouper were fed to apparent satiation twice daily during the week and once daily on weekends. Weight gain and specific growth rate increased with increasing levels of dietary lysine up to 27.2 g kg^?1 (P < 0.05) and remained nearly the same thereafter (P > 0.05). Feed efficiency was the poorest for fish fed the lowest lysine diet (P < 0.05) and showed no significant differences among other treatments (P > 0.05). Survival could not be related to dietary treatments. Body composition remained relatively constant except for lipid contents in muscle and liver. Total essential amino acid contents in liver increased with dietary lysine level although there was a slight decline for fish fed the highest lysine level of diet. Plasma protein content increased with increasing dietary lysine level (P < 0.05), but cholesterol, triacylglycerol and glucose contents were more variable and could not be related to dietary treatments. Dietary lysine level significantly influenced morphometrical parameters (condition factor, hepatosomatic index and intraperitoneal fat ratio) of juvenile grouper (P > 0.05). Broken‐line analysis of weight gain indicated the dietary lysine requirement of juvenile grouper to be 28.3 g kg^?1 diet or 55.6 g kg^?1 dietary protein.     

稚鳖赖氨酸营养的需要量

选择体重为(22.62±0.52)g稚鳖90只,平均分成6组,分别饲喂含赖氨酸为1.42、1.87、2.22、2.57、2.92和3.32%的等能等氮半合成饵料,试验期45d.结果表明,赖氨酸缺乏会降低鳖的生活力,导致其食欲下降、生长受阻、体蛋白沉积下降、肝生长受阻和赖氨酸-α-酮戊二酸还原酶活力下降(P＜0.01);赖氨酸对鳖的增重、饵料系数、体蛋白沉积量和净沉积率、体赖氨酸沉积量和净沉积率、肝重/体重和肝赖氨酸-α-酮戊二酸还原酶活力影响极显著(P＜0.01),并成极显著或显著二次回归关系(R2=0.7667-0.9594,P＜0.005～0.02).根据这些指标确定的赖氨酸需要量差异不明显,稚鳖赖氨酸需要量为2.40%或5.32g@(100gCP)-1.尽管赖氨酸对摄饵量和肝重也有极显著影响(P＜0.01),但是不呈显著二次回归关系(R2=0.3766-0.5990,P＞0.05).     

Dietary lysine requirement of juvenile gilthead seabream Sparus aurata L.*

The dietary lysine requirement of juvenile gilthead seabream was determined by the growth response of duplicate groups of fish (3.5 g initial weight) fed on six isonitrogenous (427 g kg^?1) and isolipidic (135 g kg^?1) diets containing graded levels of crystalline l ‐lysine HCl, with dietary lysine content ranging from 36.3 to 79.7 g kg^?1 of protein. The final indispensable amino acid profile of the diets except for lysine was formulated so as to resemble that of wild seabream whole body. Except for the reduced growth performance of fish groups fed the lysine‐deficient diets no other deficiency signs were apparent. Survival observed throughout the feeding period of 6 weeks was excellent. Weight gain (in %), specific growth rate, feed efficiency and daily protein deposition (DPD) were significantly improved in response to the increasing levels of dietary lysine up to 52.7 g kg^?1 of protein and remained nearly constant thereafter. Whole‐body protein content followed a similar pattern as growth parameters in relation to dietary lysine level. Non‐linear regression analysis of DPD against dietary lysine level using the four‐parameter saturation kinetic model indicated a lysine requirement of 50.4 g kg^?1 of protein for this species to support growth.     

Dietary lysine requirement of juvenile Pseudobagrus ussuriensis

An 8‐week feeding trial was conducted to determine dietary lysine requirement of juvenile Pseudobagrus ussuriensis (initial body weight: 0.60 g). Six isonitrogenous (crude protein, 400 g/kg) and isolipidic (crude lipid, 50 g/kg) diets were formulated to contain graded levels of dietary lysine (12.8, 19.9, 26.5, 34.0, 40.8 and 44.1 g/kg dry diets, respectively). The results indicated that weight gain, specific growth rate, productive protein value and protein efficiency ratio increased, while feed conversion ratio decreased with increasing dietary lysine level up to 34.0 g/kg dry diet and then levelled off. Fish fed diet with 12.8 g/kg lysine had the lowest lysine content (58.6 g/kg dry matter) in muscle, while fish fed diet with 34.0 g/kg lysine had the highest value (61.6 g/kg dry matter; p < .05). Broken‐line analysis on the basis of weight gain showed that the optimal dietary lysine requirement for maximum growth of juvenile Pseudobagras ussuriensis is 33.5 g/kg dry diet (82.4 g/kg dietary protein). Quadratic regression analysis of protein efficiency ratio against dietary lysine levels indicated that the optimal dietary lysine requirement of juvenile Pseudobagras ussuriensis is 36.4 g/kg dry diet (89.5 g/kg dietary protein).     

3种滤料生物滤器的挂膜与黑鲷幼鱼循环水养殖效果

采用微生态净水剂作为菌种,对3种生物滤料(陶环、弹性毛刷和爆炸棉)构建的生物滤器进行生物膜培养,并以3种生物滤器为基础构建简易循环水养殖系统,进行黑鲷(Sparus macrocephalus)幼鱼养殖实验。结果表明,陶环生物滤器、弹性毛刷生物滤器和爆炸棉生物滤器的生物膜成熟时间分别为25 d、32 d和28 d。黑鲷幼鱼经过40d的饲喂,3个实验组鱼的体质量与对照组相比,均差异显著(P<0.05),成活率均达到95%以上;实验组鱼血清溶菌酶(LSZ)活性和肝组织总超氧化物歧化酶(T-SOD)活性均显著高于对照组(P<0.05);实验组鱼体消化道内菌群数量及其多样性要明显高于对照组。结果表明,不同滤料在相同工况条件下挂膜成熟时间不同;微生态净水剂作为挂膜菌种效果良好;循环水系统养殖模式不仅可以提高鱼体的生长速度,还能增强鱼体免疫性能。     

Dietary lysine requirement of juvenile Protonibea diacanthus

An 8‐week experiment was conducted to determine the optimal dietary lysine requirement for juvenile Protonibea diacanthus. Six isonitrogenous and isolipidic diets were formulated to contain levels of 10.8 (L10.8), 18.2 (L18.2), 26.1 (L26.1), 33.9 (L33.9), 40.7 (L40.7) and 48.6 g/kg (L48.6) of diets and were fed to the juvenile Protonibea diacanthus, respectively. The results indicated that weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER) and final weight (FW) increased as the dietary lysine level increased from 10.8 to 26.1 g/kg and then decreased as the dietary lysine levels further increased (p < .05). The lowest feed conversion ratio (FCR) was found when dietary lysine level was 26.1 g/kg. Analysis of specific growth rate by two slope broken‐line model indicated that the estimated optimal dietary levels of lysine for juvenile Protonibea diacanthus was 23.06 g/kg (51.24 g/kg dietary protein).     

Dietary l‐lysine requirement of fingerling stinging catfish,Heteropneustes fossilis (Bloch) for optimizing growth,feed conversion,protein and lysine deposition

Dietary lysine requirement of fingerling Heteropneustes fossilis (6.96 ± 0.05 g) was quantified by conducting 12‐week feeding trial in a flow‐through system at 28°C. Casein–gelatin based isonitrogenous (38% CP) and isocaloric (14.7 kJ g^?1 DE) amino acid test diets with six levels of dietary lysine (1.5%, 1.75%, 2.0%, 2.25%, 2.5%, 3.0% dry diet) were fed to apparent satiation in triplicates. Broken‐line and second‐degree polynomial regression analyses at 95% plateau of absolute weight gain (AWG; g fish^?1), feed conversion ratio (FCR), protein deposition (PD; g fish^?1) and lysine deposition (LD; g fish^?1) exhibited lysine requirement between 2.0% to 2.3% of the dry diet, corresponding to 5.3–6.1% protein.     

黑鲷生长激素及其受体的季节变化

采用黑鲷生长激素(seabream growth hormone,brGH)放射免疫测定法(brGHRIA)及黑鲷生长激素放射受体测定法(brGHRRA)，研究了不同季节(3月、6月、9月及12月)黑鲷血清GH水平及肝脏和性腺中生长激素 受体(growth hormone receptor,GHR)水平的变化，同时测定了黑鲷白肌及肝脏RNA-DNA比率及黑鲷肥满度 (condition factor,K)和性腺指数(gonadosomatic     

Dietary histidine requirement of juvenile blunt snout bream (Megalobrama amblycephala)

An eight‐week feeding trial was conducted to determine the dietary histidine requirement of juvenile blunt snout bream. The results showed that final body weight, weight gain rate and specific growth rate significantly increased with increasing dietary histidine levels up to 9.9 g/kg (p < .05) and decreased gradually thereafter, while feed conversion ratio showed a converse trend. The survival rate, condition factor, viscerosomatic and hepatosomatic index were not significantly affected by the graded dietary histidine levels (p > .05). About 9.9 g/kg dietary histidine level significantly improved whole‐body protein and lowered moisture content. The contents of plasma total protein, cholesterol, urea and triglyceride levels were not significantly affected by dietary histidine levels. About 9.9 g/kg dietary histidine level significantly upregulated target of rapamycin and insulin‐like growth factor mRNA levels (p < .05), and 12.1 g/kg and 14.2 g/kg dietary histidine levels significantly upregulated eukaryotic translation initiation factor 4E‐binding protein 2 and ribosomal protein S6 kinase‐polypeptide 1 mRNA levels (p < .05). Based on second‐degree polynomial regression analysis of weight gain rate, and specific growth rate against dietary histidine levels, the dietary histidine requirement for juvenile blunt snout bream was estimated to be 11.2 g/kg of diet, corresponding to 36.1 g/kg of dietary protein.     

黄鳍鲷幼鱼对几种不同糖源的利用

本研究用来评价黄鳍鲷幼鱼对饲料中葡萄糖、麦芽糖、糊精、玉米淀粉和预糊化玉米淀粉的利用。本试验饲料为6种等氮(粗蛋白:45%,干重)等脂(粗脂肪:9%,干重)的半纯化饲料,其中对照组糖源为纤维素。每种饲料设3个平行。试验鱼初始体重为(3.57±0.13)g(平均值±均差)。试验鱼饲养在含18个水族箱的循环系统中。水温保持在(27±1)℃。试验周期为8周。本试验用来评价黄鳍鲷幼鱼对饲料中不同糖源利用的指标为生长指标、饲料效率、蛋白质效率和肝脏的6-磷酸葡萄糖脱氢酶、苹果酸脱氢酶、异柠檬酸脱氢酶和葡萄糖-6-磷酸脱氢酶。试验结果表明,黄鳍鲷幼鱼体增重、特定生长率、肝体比、肠系膜脂肪体比、饲料效率、蛋白质效率、肝脂肪合成有关酶活性和全鱼、肌肉、肝脏组成均受到饲料中不同糖源的显著影响。预糊化玉米淀粉和麦芽糖组比其它糖源组显著具有更好的体增重和特定生长率,但与对照组没有显著性差异。黄鳍鲷幼鱼生长和体增重与饲料中糖源的复杂性没有相关性。饲喂预糊化淀粉和对照饲料鱼的饲料效率和蛋白质效率显著比其它组高。饲料中糖的添加增加了黄鳍鲷幼鱼的肝体比,但对照组肝体比与糊精组,玉米淀粉组没有显著性差异。预糊化玉米淀粉组肠系膜脂肪体比比其它饲料组要高。结论:基于体增重和特定生长率为指标,饲料中添加25%预糊化玉米淀粉和麦芽糖可以提高黄鳍鲷幼鱼的生长。另外,玉米淀粉预糊化显著提高了黄鳍鲷对玉米淀粉的利用。     

Dietary protein requirement of white sea bream (Diplodus sargus) juveniles

A trial was undertaken to estimate the protein requirement of white sea bream (Diplodus sargus). Five fish meal‐based diets were formulated to contain graded levels of protein (from 60 to 490 g kg^?1). Each diet was assigned to triplicate groups of 25 fish with a mean individual body weight of 22 g. Fish fed the 60 g kg^?1 protein diet lost weight during the trial, while growth improved in the other groups as dietary protein level increased up to 270–370 g kg^?1. Feed efficiency improved as dietary protein level increased. Maximum protein efficiency ratio (PER) was observed with the 17% protein diet. N retention (NR) (% N intake) was not different among groups fed diets with 17% protein and above. Ammonia excretion (g kg^?1ABW day^?1) increased as dietary protein level increased, while no differences in urea excretion were noted. An exponential model was used to adjust specific growth rate and NR (g kg^?1 day^?1) to dietary protein level. Based on that model, dietary protein required for maximum retention was 330 g kg^?1, while for maximum growth it was 270 g kg^?1. On a wet weight basis, there were no differences in whole body composition of fish‐fed diets with 170 g kg^?1 protein and above, except for the protein content, which was lower in group fed the 170 g kg^?1 protein diet than the 490 g kg^?1 protein diet. Specific activities of hepatic amino acid catabolism enzymes (glutamate dehydrogenase, alanine aminotransferase and aspartate aminotransferase) increased as dietary protein levels increased. There were no differences among groups in fatty acid synthetase and malyc enzyme but 6‐phosphate dehydrogenase (G6PDH) was significantly lower in fish fed the 60 g kg^?1 protein diet than the 170 and 490 g kg^?1 protein diets.     

Effect of dietary l‐lysine levels on growth,feed conversion,lysine retention efficiency and haematological indices of Heteropneustes fossilis (Bloch) fry

Effect of varying dietary lysine levels on growth, feed conversion, nutrient retention, lysine retention efficiency and haematological indices of Heteropneustes fossilis fry (2.97 ± 0.11 cm; 4.78 ± 0.31 g) was studied by conducting a 12‐week feeding trial. Isonitrogenous (450 g kg^?1 CP) and isocaloric (17.97 kJ g^?1 GE) amino acid test diets with graded concentrations of l ‐lysine (18, 20, 22, 24, 26, 28 g kg^?1 dry diet) were fed to triplicate groups of fish to apparent satiation twice daily at 17 and 17:30 h. Maximum thermal growth coefficient (TGC, 0.82), best feed conversion ratio (FCR, 1.28) highest protein retention efficiency (PRE, 36%), energy retention efficiency (ERE, 79%) and lysine retention efficiency (LRE, 75%) were noted at 24 g kg^?1 lysine of dry diet. Body protein was also found to be in line with growth data and peaked at 24 g kg^?1 lysine of dry diet. Similarly, superior somatic and haematological indices were exhibited by the groups fed dietary lysine at 24 g kg^?1 of the dry diet. However, exponential analysis of dietary lysine intake against TGC, lysine retention and protein retention indicated that inclusion of dietary lysine in the range of 13.24–14.14 g kg^?1 dry diet, corresponding to 29.42–31.42 g kg^?1 dietary protein, is essential for faster growth of this fish.     

赖氨酸对团头鲂幼鱼生长、血清生化及游离必需氨基酸的影响

为探讨饲料中不同水平赖氨酸对团头鲂幼鱼生长、血清生化及血清中游离必需氨基酸的影响,选用初始均重(3.34±0.03)g的团头鲂幼鱼540尾,随机分成6个实验组,每个实验组3个重复,每个重复30尾鱼,分别投喂赖氨酸含量为1.29%、1.71%、2.09%、2.48%、2.88%、3.27%的饲料,养殖实验为10周。研究表明:(1)与对照组相比,2.48%赖氨酸实验组显著提高了团头鲂幼鱼的鱼体末重、增重率、特定增重率、氮沉积率、蛋白质效率和蛋白沉积率,显著降低了饵料系数,但不影响存活率;(2)2.09%赖氨酸实验组显著提高鱼体蛋白含量和降低脏体比系数,2.88%、3.27%赖氨酸实验组显著降低了粗灰分含量;(3)3.27%赖氨酸实验组显著提高了血清中谷丙转氨酶和总蛋白含量;2.14%赖氨酸实验组显著降低了血清中白蛋白的含量;2.88%赖氨酸实验组显著降低了血清中尿素含量;(4)除血清亮氨酸和缬氨酸之外,2.88%赖氨酸实验组显著提高了血清中必需氨基酸含量;同时,随着饲料中赖氨酸水平的增加,血清中总必需氨基酸呈先升高后趋于平缓的趋势。以鱼体特定增重率和蛋白沉积率为评价指标,经折线模型回归分析得到团头鲂幼鱼饲料中赖氨酸的适宜添加量分别为饲料干重的2.36%(饲料粗蛋白含量的6.96%)和2.22%(饲料粗蛋白含量的6.53%)。     

d‐lysine can be effectively utilized for growth by common carp (Cyprinus carpio)

An 8‐week feeding trial was conducted to compare the effects of different lysine isomers on growth, nutrient utilization and metabolic enzyme activity in common carp (Cyprinus carpio). A basic experimental diet (the control group) with 30% of dietary protein from fish meal and the remaining 70% from soybean meal was used either with or without supplementation of d‐ lysine, l‐ lysine or dl‐ lysine, respectively. The total feed intake was significantly improved by supplementation with lysine regardless of isomeric form (P < 0.05). Supplementation with d‐ lysine or l‐ lysine (but not dl‐ lysine) generally increased the weight gain, specific growth rate, feed efficiency ratio and protein efficiency ratio. Dietary lysine supplementation generally increased the apparent digestibility of dry matter, crude protein and crude lipid, but no statistically significant differences were observed between the control group and the lysine‐supplement groups (P > 0.05). The d‐ amino acid oxidase and d‐ aspartate oxidase activities were generally higher in the liver, kidney and intestine of fish fed diet containing d‐ lysine compared to fish fed diet containing l‐ lysine. The lysine, protein and lipid gains in fish were markedly increased by the supplementation with d‐ lysine or l‐ lysine, and the lysine (r = 0.618, P < 0.05) and protein gains (r = 0.671, P < 0.05) were linearly related to dietary lysine intake. Lysine retention efficiency linearly decreased with the increase of dietary lysine intake (r = ?0.579, P < 0.05). These results indicate that common carp are capable of utilizing the supplemental crystalline d‐ lysine·HCl (4 g kg^?1 dry diet) for growth when the rest of dietary amino acids are protein‐bound forms.