Influence of dietary protein levels on growth performance and body composition of African bonytongue fingerlings,Heterotis niloticus (Cuvier, 1829)

Two experiments were conducted to examine the influence of dietary protein levels on growth and carcass proximate composition of Heterotis fingerlings. Four isoenergetic practical diets were formulated to contain dietary protein levels from 250 to 400 g kg^?1 diet. Replicate groups of young Heterotis (initial live weight 3.96 and 26.40 g in experiments 1 and 2 respectively) were handfed twice daily to apparent satiation for a period of 42 and 28 days respectively. Statistical analysis revealed that growth rate was significantly affected by dietary protein level (P < 0.01). The highest weight gain was observed in fingerlings fed with 300 and 350 g protein kg^?1 diet for fish size ranging between 3–15 and 26–62 g respectively. There was no significant difference between groups fed with 300, 350 and 400 g protein kg^?1 diet for Heterotis fingerlings (3–15 g) in the one hand; in the other hand, significant differences were found between fish (26–62 g) fed with 350 g protein kg^?1 diet and those receiving 300 and 400 g protein kg^?1 diet, with no significant difference between each other. The specific growth rate varied from 2.4% to 3.1% day^?1. The whole‐body protein, lipid, moisture and ash contents were not significantly affected by dietary protein levels (P > 0.05). The relationships between percentage weight gain and dietary protein levels suggested very similar dietary protein requirement (about 310 g crude protein kg^?1 diet) for Heterotis ranging from 3 to 62 g. The maximum growth occurred at about 345 g protein kg^?1 diet.     

Effects of dietary tryptophan levels on growth performance,whole body composition and gene expression levels related to glycometabolism for juvenile blunt snout bream,Megalobrama amblycephala

To investigate the effects of dietary tryptophan on growth and glycometabolism in juvenile blunt snout bream, 450 fish (initial weight 23.33 ± 0.03 g) were fed six practical diets with graded levels of tryptophan (from 0.79 g/kg to 5.96 g/kg dry matter) for 8 weeks. Results showed that final weight, per cent weight gain (PWG), protein efficiency rate, feed intake and feed conversion ratio (FCR) were significantly improved by 2.80 g/kg diet. The maximum values of protein and ash were observed in 2.80 g/kg diet, while moisture was minimum. Lipid content of fish fed 3.95 g/kg diet was significantly higher than other diets. The highest plasma insulin‐like growth factor‐1 (IGF‐1) content was observed in 0.79 g/kg diet. In the liver, IGF‐1 mRNA levels were significantly downregulated by 2.80 g/kg dietary tryptophan, while glucokinase levels were by 3.95 g/kg, while glucose‐6‐phosphatase and phosphoenolpyruvate carboxykinase mRNA levels showed a converse trend compared with IGF‐1. Based on PWG and FCR, the optimal dietary tryptophan level was determined to be 1.99 g/kg (6.20 g/kg of dietary protein) and 1.96 g/kg (6.11 g/kg of dietary protein), respectively, using broken‐line regression analysis.     

饲料蛋白质和脂肪水平对赤眼鳟生长和鱼体营养成分的影响

采用3×3因子试验设计,配制9种试验饲料,研究饲料不同蛋白质水平(31%、37%和43%)和脂肪水平(3.5%、5.5%、7.5%)对平均体重为5.49 g赤眼鳟(Squaliobarbus curriculus)鱼种生长和鱼体组成的影响。实验选取赤眼鳟鱼种810尾,随机分成9组,每组2个重复,饲养期6周。结果显示:饲料蛋白质和脂肪的交互作用对赤眼鳟的特定生长率有显著影响(P<0.05),饲料蛋白质水平对饲料系数影响显著(P<0.05),当饲料蛋白质水平为37%、脂肪水平为3.5%时赤眼鳟特定生长率最大,饲料系数最低。随着特定生长率的升高,赤眼鳟的肥满度和肌肉蛋白质的含量升高;赤眼鳟肌肉和肝脏脂肪含量均随着饲料中可消化能的增加而增加。     

Effect of dietary protein on growth, feed conversion, body composition and survival of pike perch fingerlings (Sander lucioperca)

Triplicate groups of pike perch (Sander lucioperca) juveniles were fed six experimental diets containing protein levels varying from 263 to 619 g kg⁻¹ dry matter (d.m.) for 56 days. Dietary protein was supplied by graded amounts of fish meal (with 720 g kg⁻¹ crude protein). Crude lipid and gross energy content of 101–107 g kg⁻¹ and 19.9–20.6 MJ kg⁻¹ remained constant between experimental diets. Pike perch with an initial body weight of 1.05 ± 0.05 g were randomly distributed in 18 tanks of two similar recirculation systems and fed on gradually decreasing feeding rates of 10 to 6% of their body weight per day. Growth performance and feed conversion increased with dietary protein level from 263 to 549 g kg⁻¹ d.m. but did not decline at highest dietary protein level. Protein efficiency ratio declined linearly with increasing dietary protein. Survival ranged between 89.7 and 93.9% and was not affected by dietary composition. Dry matter and crude lipid content of pike perch fingerlings decreased with increasing dietary protein supply and significantly the lowest dry matter and crude lipid levels were observed in fish fed diets containing 619 g kg⁻¹ of crude protein. The dietary protein requirement for pike perch fingerlings calculated by broken‐line and second‐order polynomial regression ranged between 529 and 577 g kg⁻¹, respectively.     

Effects of dietary protein and lipid levels with different protein‐to‐energy ratios on growth performance,feed utilization and body composition of juvenile red‐spotted grouper,Epinephelus akaara

An 8‐week feeding trial was conducted to assess dietary protein and lipid levels on growth performance, feed utilization and body composition of juvenile red‐spotted grouper (7.85 ± 0.03 g fish^?1). Nine semi‐purified diets were formulated containing varying protein levels (440–520 g kg^?1, dry matter) and lipid levels (60–120 g kg^?1, dry matter). The weight gain of juvenile Epinephelus akaara was affected by dietary protein (p = .005) and its interaction with dietary lipid (p = .020). Viscerosomatic index, intraperitoneal fat ratio and whole‐body lipid level increased with increasing dietary lipid level (p < .001). Nitrogen retention was not affected by dietary protein and lipid, while lipid retention decreased with increasing dietary lipid level (p < .001). The plasma blood urea nitrogen increased with increasing dietary protein level (p = .003). This study showed that diet with 520 g kg^?1 protein and 60 g kg^?1 lipid with 30.58 mg kJ^?1 P:E provided a maximal growth for this species. Moreover, an increase in dietary lipid levels (from 60 to 90 g kg^?1) could reduce the protein requirement (from 520 to 480 g kg^?1) without affecting the growth performance, while higher fat deposition was observed in fish fed high‐lipid diets.     

Effects of varying dietary protein to lipid ratios on growth performance and body composition of juvenile pike perch (Sander lucioperca)

The present study investigated the effect of varying dietary protein‐to‐lipid ratios (P/L) on growth performance and body composition of pike perch (Sander lucioperca) fingerlings with an initial body weight of 1.35–1.40 g. Triplicate groups were reared during 56 days in recirculation systems and fed six experimental diets containing three dietary levels of lipid (90, 130, 170 g kg^?1 of dry matter, d.m.) combined with two levels of dietary protein (470, 540 g kg^?1 d.m.). During the experimental period the fixed feeding rates decreased from 10% to 5% of the total fish biomass per day. In contrast to previous results obtained with this species, the present study clearly demonstrated the occurrence of protein sparing effect. The best results for feed conversation ratio and specific growth rates were obtained in the treatments containing highest lipid level: diet 3 (P/L 47/17) and diet 6 (P/L 53/17). The d.m. and crude lipid contents of pike perch whole body increased in direct proportion of the dietary lipid levels. No difference was observed on crude protein and ash content among the treatments. Increasing hepatosomatic index at highest dietary lipid level suggested a limited lipid utilization of percids.     

饲料蛋白质水平对拟穴青蟹幼蟹生长性能、体成分和消化酶活性的影响

用蛋白质水平分别为31.45%,36.37%,41.55%,46.13%,51.72%和56.86%的6种等能饲料,对初始体重为(11.86?0.11)mg的拟穴青蟹(Scylla paramamosain)幼蟹进行为期3周的养殖实验,考察饲料蛋白质水平对拟穴青蟹幼蟹生长性能、体成分以及消化酶活性的影响,以期获得拟穴青蟹幼蟹饲料蛋白质的适宜添加量。结果表明,饲料蛋白质水平对拟穴青蟹幼蟹的成活率影响不显著(P0.05);幼蟹的增重率和特定生长率随饲料蛋白质水平的提高先显著升高(P0.05)后稍有下降,最大值出现在蛋白质水平为51.72%的实验组;随着饲料蛋白质水平的提高,幼蟹粗蛋白质含量显著升高(P0.05)后趋于稳定,粗脂肪含量显著降低(P0.05),灰分含量先显著升高(P0.05)后显著降低(P0.05),水分含量则没有显著变化(P0.05);随着饲料蛋白质水平的提高,幼蟹蛋白酶活性显著升高(P0.05),淀粉酶活性显著降低(P0.05),各组脂肪酶活性也有显著差异(P0.05),但没有明显的变化规律。本研究条件下,饲料蛋白质水平在41.55%~56.86%,拟穴青蟹幼蟹均表现出较好的生长率,增重率和蛋白质水平的回归分析表明,幼蟹饲料蛋白质适宜水平为49.03%。     

Effects of dietary protein and lipid levels on growth performance and body composition of black sea bass Centropristis striata (Linnaeus 1758) during grow-out in a pilot-scale marine recirculating system

The influence of four formulated practical diets, with different protein and lipid levels, on the growth and body composition of black sea bass ( Centropristis striata L.) pre-adults was evaluated in a pilot-scale marine recirculating system. Four test diets were prepared with a combination of two protein levels (44% and 54%) and two lipid levels (10% and 15%). The diets were as follows: low protein and low lipid (LP:LL; 44:10), low protein and high lipid (LP:HL; 44:15), high protein and low lipid (HP:LL; 54:10) and high protein and high lipid (HP:HL; 54:15). Fish (mean weight=75.5 g) were fed the respective diets for 90 days. For fish fed LP:HL, body weight gain was significantly ( P <0.05) higher than fish fed LP:LL. Increasing the protein level from 44% to 54% did not produce a significant effect on weight gain at high lipid level. A significant ( P <0.01) interactive effect between dietary protein and lipid levels on the growth and feed utilization was observed. Total lipid content in the whole body, muscle and liver was significantly affected by the dietary lipid levels. The results suggested that a combination of 44% dietary protein and 15% lipid was optimal for the growth of black sea bass.     

饲料中赖氨酸水平对克氏原螯虾生长、体组成与消化酶活性的影响

克氏原螯虾(Procambarus clarkii)购自盱眙某龙虾养殖场,初始体质量为(7.60±0.01)g。以酪蛋白、明胶、小麦面筋粉和晶体氨基酸为蛋白源配制7组蛋白质水平为28.26%、能量为17.15 kJ.g 1的等氮等能半纯和饲料,各组赖氨酸质量分数分别为0.76%、1.00%、1.22%、1.47%、1.69%、1.89%和2.18%。实验虾分为7组,每组设4个重复,每个重复12尾虾,分别投喂以上7种饲料。养殖实验于室外网箱(规格为60 cm×60 cm×60 cm)中进行,饲养周期为60 d。结果表明,随着饲料中赖氨酸水平的升高,增重率、特定生长率和饲料效率均显著升高(P<0.05),分别在赖氨酸水平1.69%、1.69%和1.22%组时,三者达到最大值;当赖氨酸水平进一步升高,三者均呈下降趋势。各组的成活率为89.58%~97.92%,组间无显著差异(P>0.05)。全虾水分含量以赖氨酸水平1.22%组最低,显著低于0.76%组(P<0.05)。全虾粗蛋白和粗脂肪含量分别以赖氨酸水平1.89%组和1.69%组最高,均显著高于0.76%组(P<0.05)。各组之间的全虾灰分含量、肌肉组成、肌肉氨基酸组成和消化酶活性均无显著差异(P>0.05)。以增重率为评价指标进行一元二次回归分析,得出克氏原螯虾的适宜赖氨酸需求量为1.66%,占饲料蛋白的5.87%。本研究旨在通过确定克氏原螯虾对饲料中赖氨酸的适宜需求量,为其人工配合饲料的研制提供基础数据和理论依据。     

摄食不同饵料对翘嘴鳜生长、体成分和消化酶活性的影响

为探究三种不同饵料对翘嘴鳜(Siniperca chuatsi)生长性能、体成分和消化酶的影响,实验选取初始体重为(113.56±11.82)g的翘嘴鳜900尾,随机分成3组,分别投喂活饵料鱼、冰鲜饵料鱼和商品饲料,进行60 d的养殖试验。结果显示:(1)冰鲜组、活饵组和饲料组翘嘴鳜的成活率、增重率、特定生长率和蛋白效率均无显著性差异。饲料组翘嘴鳜肥满度显著小于其他两组,肝体比和脏体比均显著大于其他两组。(2)三组翘嘴鳜体成分中的水分、蛋白质、粗脂肪和粗灰分均没有显著性差异。(3)翘嘴鳜肌肉各种氨基酸含量和总氨基酸量在三组之间的差异均不显著。饲料组翘嘴鳜肌肉中不饱和脂肪酸中的棕榈油酸、油酸、亚油酸、花生烯酸、EPA、神经酸、DHA的含量及总饱和脂肪酸、总单不饱和脂肪酸、总多不饱和脂肪酸均显著高于其他两组。(4)肝脏脂肪酶、肠道淀粉酶的活性在三组翘嘴鳜之间均没有显著性差异。冰鲜组翘嘴鳜肝脏淀粉酶、肠道脂肪酶活性均显著高于其他两组。结果表明:翘嘴鳜经过驯化可以摄食配合饲料,且不影响其生长性能。翘嘴鳜摄食饲料后,其肌肉氨基酸没有发生显著性的变化,不饱和脂肪酸的含量显著升高。     

Growth and body composition of juvenile largemouth bass Micropterus salmoides in response to dietary protein and energy levels

To determine the dietary protein and energy requirements of juvenile largemouth bass, 1350 feed‐conditioned fishes (average weight 14.46 ± 0.81 g) were stocked in ninety 60‐L cages, set up in 1000‐L tanks at three cages/tank, and fed for 64 days with a dry, extruded feed containing six levels of crude protein (CP) (340–540 g kg^–1, with increases of 40 g kg^–1) and five levels of energy (150.7–171.7 kJ g^–1 feed, with increases of 5.2 kJ). The trial was set up in a 6 × 5 factorial, completely randomized design (n=3). Weight gain (WG), daily feed consumption (DFC), feed conversion rate (FCR), protein efficiency ratio (PER), specific growth rate (SGR), protein and energy retention were recorded and evaluated. There was no interaction between feed energy and protein levels with all parameters evaluated. Data analysis by the broken line method showed that the minimum dietary requirement for maximum daily weight gain of 8.0 g kg^–1 is 435.9 g kg^–1 CP; the best feed conversion ratio (1.04:1) was attained with a minimum of 448.2 g kg^–1 CP; a minimum of 162.1 kJ g^–1; DFC was reduced as dietary protein and energy levels increased; dietary levels of 460–500 g kg^–1 CP led to best PER (1.665); best values for protein (33.14 g 100 g^–1) and energy (26.87 g 100 g^–1) retention were observed for fish feeding on the 420 g kg^–1 CP ration. Limits of energy to protein ratio to feed largemouth bass are 25.01 and 26.89 mg protein kJ^–1, enabling feed conversion ratios of 0.96–1.10.     

饲料糖水平对眼斑双锯鱼幼鱼生长性能和体成分的影响

为确定眼斑双锯鱼(Amphiprion ocellaris)幼鱼人工配合饲料的适宜糖水平,研究了糖水平为4.4%、8.4%、12.2%、16.1%、20.5%、24.5%和28.4%的人工饲料对眼斑双锯鱼幼鱼生长、饲料转化率和体成分的影响。结果显示,随着糖水平的升高,幼鱼增重率(WG)和特定生长率(SGR)呈先增加后降低趋势。回归分析表明,糖水平16.49%时WG最大;糖水平16.73%时SGR最大。饲料系数(FCR)随糖水平增加呈现先下降后上升的趋势,而蛋白质效率(PER)、蛋白质沉积率(PRR)和脂肪沉积率(LRR)的变化则相反。回归分析显示,糖水平9.20%时FCR最小;糖水平8.57%时PER最大;糖水平10.97%时PRR最大;糖水平14.12%时LRR最大。全鱼粗脂肪质量分数随糖水平升高而增加,糖水平20.5%时达到最高水平后略有下降。综合生长参数与糖水平的回归分析结果,眼斑双锯鱼生长最快的糖添加量为16.49%~16.73%;综合饲料效率参数与糖水平的回归分析结果,饲料效率最高的糖添加量为8.57%~14.12%。     

肉碱对草鱼生长性能、体成分和脂肪代谢酶活性的影响

在基础饲料中分别添加100、200、300和400mg/kg DL-肉碱,饲喂平均体重134.3±12.1g的草鱼(Ctenopharyngodon idella)8W,以增重率、饲料系数(FCR),肌肉和肝胰脏中蛋白脂肪含量,肠道脂肪消化酶,肝胰脏脂蛋白脂酶(LPL)、肝脂酶(HL)和脂肪酸合成酶(FAS)等指标为判据,研究肉碱对草鱼生长性能、体成分和脂肪代谢酶活性的影响。结果表明,添加200mg/kg肉碱提高鱼体增重率5.70%(P < 0.05),降低FCR5.26%(P < 0.05);添加200～400mg/kg肉碱显著降低了肌肉和肝胰脏中的脂肪含量(P < 0.05);当肉碱添加量为300mg/kg时,肌肉蛋白含量最高;肉碱对肌肉水分和灰分、肝胰脏的蛋白含量无影响(P > 0.05);添加200、400mg/kg肉碱显著降低了血清胆固醇含量(P < 0.05);在脂肪代谢酶活性方面,200mg/kg肉碱组肠道脂肪消化酶和HL活性较对照组提高28.0%、38.6%(P < 0.05);添加400mg/kg肉碱提高肠道脂肪消化酶、HL及总脂酶活性41.41%、36.26%、10.66%(P < 0.05),降低FAS活性47.3%(P < 0.05)。综上所述,适量肉碱能改善草鱼生长性能、降低肌肉和肝胰脏脂肪含量及促进脂肪降解。建议草鱼饲料中肉碱添加量为200mg/kg。     

Influence of dietary protein levels on growth performance, carcass composition and liver lipid classes of juvenile Spinibarbus hollandi (Oshima)

A feeding trial was conducted to investigate the influence of dietary protein levels on growth performance, carcass proximate composition and liver lipid classes of juvenile Spinibarbus hollandi (Oshima), a cyprinid fish. White fish meal was the primary protein source in the study. Eight experimental diets containing 13–55% crude protein were fed to three replicate groups of six fish weighing nearly 8.5 g each for 10 weeks. Both percentage weight gain and feed efficiency ratio increased significantly with increasing dietary protein levels up to 31%, but there was no further increase for protein levels from 31% to 55%. Application of broken‐line regression analysis to the percentage weight gain provided an estimate of 32.7±1.5% dietary protein for maximum growth. The protein efficiency ratio and productive lipid value were inversely correlated with dietary protein level. The hepatosomatic index and the viscerosomatic index were also inversely related to dietary protein level. The carcass protein of fish fed lower protein diets was significantly lower than that of the fish fed higher protein diets. Carcass lipid content decreased with increasing dietary protein levels, whereas moisture was inversely related to lipid content. Both liver glycogen and liver lipid contents decreased with increasing dietary protein levels. Triglyceride was the major component in the liver lipid, and the amount of triglyceride deposited in the liver also decreased with dietary protein levels. The results indicated that both carcass proximate composition and liver lipid class of juvenile Spinibarbus hollandi were affected by dietary treatments.     

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%。     

Effects of dietary protein and lipid levels on growth, feed conversion and body composition in rohu, Labeo rohita (Hamilton), fingerlings

Twelve experimental diets (D‐1 to D‐12) in a 4 × 3 factorial design (four protein levels: 250, 350, 400 and 450 g kg^?1 and three lipid levels: 50, 100 and 150 g kg^?1) were formulated. Carbohydrate level was constant at 250 g kg^?1. Rohu fingerlings (average wt. 4.3 ± 0.02 g) were fed the experimental diets for 60 days in three replicates at 2% BW  day^?1. Weight gain (%), specific growth rate (% day^?1) and feed gain ratio (FGR) indicated that diets containing 450 g kg^?1 protein and 100 or 150 g kg^?1 lipid (diets D‐11 and D‐12) resulted in best performance, although results were not significantly different from those of diet D‐9 (400 g kg^?1 protein and 150 g kg^?1 lipid). Protein efficiency ratio was highest with diets D‐6 (350 g kg^?1 protein and 150 g kg^?1 lipid) and D‐9 (400 g kg^?1 protein and 150 g kg^?1 lipid) (P > 0.05) and declined with higher and lower protein diets at all levels of lipid tested. Elevated lipid level (50, 100 or 150 g kg^?1) did not produce better FGR in diets containing 400 and 450 g kg^?1 dietary protein (P > 0.05). The combined effects of protein and lipid were evident up to 400 g kg^?1 protein. Growth and FGR showed consistent improvement with increased lipid levels from 50 to 150 g kg^?1 at each protein level tested except with diets containing 450 g kg^?1 protein. Apparent nutrient digestibility (for protein, lipid and energy) did not show significant variation among different dietary groups (P > 0.05). Whole body protein and lipid contents increased significantly (P > 0.05) with dietary protein level. The results of this study indicate that rohu fingerlings are adapted to utilize high protein in diets with varying efficiency. The fish could utilize lipid to spare protein but there is no significant advantage from this beyond the dietary protein level of 350–400 g kg^?1 in terms of growth and body composition.     

Effects of dietary protein levels on the growth,body composition,serum biochemistry and digestive enzyme activity in Chinese rice field eel (Monopterus albus) fingerlings

A 12‐week feeding trial was conducted to determine the influence of dietary protein levels on growth performance, body composition, haematological parameters and digestive enzyme activity of Chinese rice field eel (Monopterus albus) fingerlings. Six isolipidic experimental diets (27.89%, 32.23%, 35.95%, 40.06%, 43.31% and 46.53%) were formulated to randomly assign to triplicate groups of 50 rice field eel fingerlings (5.0 ± 0.5 g) cultured in plastic cages. Results indicated that the best growth performance of fish with the highest WG (158.68 ± 31.59%) and SGR (2.28 ± 0.21%) was obtained at 40.06% group. Significant alterations were demonstrated on whole‐body crude protein, crude lipid and amino acid profile by different dietary protein levels. Besides, haematological parameters including triacylglycerol, aspartate aminotransferase and alkaline phosphatase decreased with various levels by the increasing of dietary protein levels. The lowest pepsin activity was observed in 27.89% protein group, which suggested lower availability of protein as substrate for protease activity. Meanwhile, the highest amylase activity in fish of 27.89% group indicated higher carbohydrate level in this group. Based on the polynomial regression analysis of WG and SGR, the dietary protein requirement for fingerlings of Monopterus albus was estimated to be 386.4–390.8 g/kg, respectively, with the lipid level of 10.08%.     

Optimal dietary protein levels in juvenile Senegalese sole (Solea senegalensis)

A study was undertaken to determine the dietary protein level for optimal growth performance and body composition of juvenile Senegalese sole. Five experimental extruded diets were formulated to contain increasing levels of protein [430, 480, 530, 570 and 600 g kg^?1 dry matter (DM)] and a constant lipid level, ranging from 100 to 130 g kg^?1 DM. Triplicate groups of 35 sole (initial body weight: 11.9 ± 0.5 g) were grown over 84 days in 60‐L tanks supplied with recirculated seawater. Fish were fed by means of automatic feeders in eight meals per day. At the start and end of the trial, whole‐body samples were withdrawn for proximate composition analysis. At the end of 84 days of experimental feeding, daily weight gain and specific growth rate in fish fed diets P43 and P48 were significantly lower than those found in fish fed higher protein level diets (P53, P57 and P59). Similarly, feed efficiency was also significantly lower in fish fed diet P43 than in fish fed all other dietary treatments. Sole juveniles fed lower protein level diets (P43 and P48) showed a significantly lower protein content than fish fed the higher dietary protein level treatments (P53, P57 and P60). Changes within the tested dietary protein levels did not affect significantly protein productive value or total nitrogen (N) losses in fish. However, daily N gain was significantly higher (P < 0.05) in fish fed diets P53 and P60 than in fish fed the lowest protein level diet (P43). Data from the present study indicate that diets for juvenile Senegalese sole should include at least 53% crude protein to maintain a good overall growth performance. Based on a second‐order polynomial regression model, the daily crude protein requirement for maximum whole‐body N gain as estimated here for Senegalese sole juveniles was 6.43 g kg^?1 body weight day^?1 which corresponds to a value of 1.03 g N intake kg^?1 body weight day^?1. If the present data are expressed on a dietary crude protein concentration basis, the allowance for maximum protein accretion (N gain) would be met by a diet containing a crude protein level of 600 g kg^?1.     

饲料脂肪水平对胭脂鱼幼鱼生长、体组成和抗氧化能力的影响

试验选用体重(6.73±0.21)g的胭脂鱼(Myxocyprinus asiaticus)幼鱼540尾,随机分成6个组,每组3个重复,每个重复30尾试验鱼。以大豆油为脂肪源,配制成脂肪水平为2.04%、4.43%、6.88%、9.02%、11.98%、13.39%的半精制饲料,进行为期56 d的生长试验,研究脂肪水平对胭脂鱼幼鱼生长、体组成及机体抗氧化能力的影响。结果显示:饲料脂肪水平对胭脂鱼的生长性能有显著影响(P<0.05)。脂肪水平为6.88%时,胭脂鱼增重率、特定生长率、蛋白质沉积效率最高,饲料系数最低。脂肪沉积效率随脂肪水平的增加呈下降趋势。随脂肪水平增加,胭脂鱼全鱼、肌肉和肝胰脏脂肪含量逐渐上升,至6.88%组后稳定,而全鱼水分、粗蛋白含量没有显著变化(P>0.05)。胭脂鱼机体抗氧化能力随着脂肪水平的增加呈现先升后降趋势,脂肪水平为6.88%时,总抗氧化能力(T-AOC)、超氧物歧化酶(SOD)值最大,丙二醛(MDA)值最小,即抗氧化能力最强。以增重率、特定生长率和饲料系数进行回归分析并考虑脂肪水平对胭脂鱼营养组成和抗氧化能力的影响,确定胭脂鱼幼鱼适宜脂肪水平为6.62%~7.02%。     

Effect of graded levels of dietary thiamine on the growth performance,body composition and haemato‐biochemical parameters of juvenile Sclizothorax prenanti

This study was conducted to determine dietary thiamine requirement of juvenile Sclizothorax prenanti and evaluate the effect of dietary thiamine levels on growth performance, body composition and haemato‐biochemical parameters for this fish species. The seven experimental diets were formulated to contain the graded levels of thiamine (0, 10, 20, 30, 40, 60 and 100 mg kg^?1 diet, respectively), providing the actual dietary thiamine values of 0.31 (control), 9.82, 21.49, 29.83, 41.66, 62.24 and 114.58 mg kg^?1 diet, respectively. Each diet was assigned to three replicate groups of S. prenanti (initial body weight: 13.46 ± 0.28 g, means ± SD) for 60 days. Increasing dietary thiamine level up to 21.49 mg kg^?1 diet increased weight gain rate (WGR), specific growth rate (SGR), feed efficiency (FE) and protein efficiency ratio (PER) (P < 0.05), beyond which they remained nearly unchanged. Similarly, hepatic thiamine concentration and several serum biochemical parameters (transketolase activity, triglyceride and total cholesterol contents) increased with increasing levels of thiamine up to 21.49 mg kg^?1 diet (P < 0.05) and, thereafter, remained almost constant. However, no significant differences in body composition (moisture, protein, lipid and ash contents) were found among dietary thiamine treatments (P > 0.05). Analysis by the broken‐line regression of WGR, SGR, FE, PER, hepatic thiamine concentration and serum transketolase activity indicated that dietary thiamine requirements in juvenile S. prenanti were 18.45–25.91 mg kg^?1 diet.