The influence of feed supply time on the fatty acid profile of Nile tilapia (Oreochromis niloticus) fed on a diet enriched with n-3 fatty acids

The purpose of the study was to examine the fatty acid profiles of Nile tilapia (Oreochromis niloticus) submitted to different feeding times (0, 10, 20 and 30 days) on a diet enriched with n-3 fatty acids, by addition of flaxseed oil in substitution for sunflower oil. The main fatty acids detected were palmitic (C16:0), stearic (C18:0), oleic (C18:1n9), linoleic (C18:2n6) and -linolenic (C18:3n3) in all the treatments. The 30 day-fed fish presented the best values for total n-3 fatty acids, with a prominence of -linolenic acids, showing that the flaxseed oil as well as the feed supply time influenced the fatty acid profiles.     

Incorporation of Alpha‐Linolenic Acid and Enhancement of n‐3 Fatty Acids in Nile Tilapia: a Factorial Design

A 2² factorial design (two factors at two levels, in triplicate) was performed to investigate the influence of factors A (time of treatment, 15 and 30 days) and B (chia oil content in a supplemented diet, at 2.1 and 4.2 %) in three responses of interest referring to: (a) the incorporation of alpha‐linolenic acid (LNA) in lipids of Nile tilapia fillet; (b) the enhancement of n‐3 fatty acids; and (c) the decrease in the omega‐6/omega3 (n‐6/n‐3) ratio in fish. Factors A and B were significant in the three regression models obtained and the interaction AB was a significant contributor to the LNA and n‐6/n‐3 ratio. Analysis of variance suggested three significant and predictive mathematical models. Response surfaces analyses from designs indicated higher LNA and n‐3 contents and a lower n‐6/n‐3 ratio using both factors A and B in the higher levels (30 days of treatment and 4.2 % of chia oil in the diet for fish) chosen for this study.     

饲料中添加牛至精油对红罗非鱼货架期的影响

研究牛至精油对红罗非鱼品质和货架期的影响。以空白添加组为对照,分别在对照组饲料中添加250、500、1 000、2 000 mg/kg牛至精油,经过20周养殖实验,红罗非鱼在4℃条件下冷藏0、7、14、21 d,在每个冷藏时间点检测红罗非鱼物理化学特性、微生物定性定量分析和感官分析评估,以判定其腐败程度。结果表明,牛至精油添加对红罗非鱼体色、硫代巴比妥酸反应值和总挥发性盐基氮含量有显著的影响。1 000、2 000 mg/kg牛至精油可有效降低冷藏鱼片的肠杆菌和大肠菌群数量。感官分析表明,红罗非鱼体的质量指数与牛至精油的添加量没有显著相关,对照组的货架期为16 d,牛至精油组的货架期为18 d,但与添加量无显著相关。     

蛋氨酸水平对罗非鱼蛋白质代谢及血清生化指标的影响

为了探讨不同蛋氨酸水平对罗非鱼生长过程中蛋白质代谢及血液生化指标的影响。通过在半精制基础饲料中添加包膜DL-蛋氨酸,配制成蛋氨酸水平分别为0.26%、0.55%、0.85%、1.14%、1.44%和1.73%的6种等氮等能(32.09%粗蛋白质,17.82 kJ/g总能)的试验饲料。以初始体质量(66.76±2.29)g的罗非鱼为试验对象,每种试验饲料设3个重复,每个重复放养试验鱼25尾,养殖系统为室内养殖系统,每天表观饱食投喂3次,养殖时间为60 d。结果表明,随饲料蛋氨酸水平的增大,罗非鱼的增重率(WGR)、饲料蛋白沉积率(PDR)及脂肪沉积率(LDR)均呈现先上升后下降的趋势。且WGR和LDR均在蛋氨酸水平为1.14%时达到最大(分别为361.91%和107.54%);PDR则在饲料蛋氨酸水平为1.44%时达到最大(47.22%)。随着饲料中蛋氨酸水平的提高,罗非鱼肝脏中的肝脏中谷草转氨酶(AST)、谷丙转氨酶(ALT)活性及AST/ALT比值均呈先升后降的变化趋势。当蛋氨酸添加水平为1.14%时,罗非鱼肝脏中AST、ALT、AST/ALT均达到最高(分别为165.33 U/mg、48.38 U/mg和3.43);肝脏中谷氨酸脱氢酶(GDH)活性及血氨水平均随着饲料中蛋氨酸水平的提高呈先降后升的变化趋势,且当蛋氨酸添加水平为1.14%时均达到最低(分别为103.97 U/mg和564.72μmol//L)(P0.05)。随饲料蛋氨酸水平的增加,罗非鱼血清中胆固醇(CHO)、甘油三酷(TG)均随饲料蛋氨酸水平的升高而呈先升高后稳定的变化趋势。说明适宜的蛋氨酸水平有利于促进机体的蛋白质和脂质代谢,提高罗非鱼的生长速度。     

Effect of Dietary Replacement of Soybean Oil with Different Sources of Gamma‐Linolenic Acid on Fatty Acid Composition of Nile Tilapia

Gamma‐linolenic acid (GLA) plays an important role in the prevention and/or treatment of certain diseases. In this work, we investigate the incorporation of GLA from supplemented feed diets with borage oil (BO) and evening primrose oil (EPO) as substitutes for soybean oil (SO) into the composition of tilapia fillet lipids. High contents of PUFA and n‐6 fatty acids were quantified in fish fillet after 30 days of treatment with SO, BO, and EPO. Feed diets containing BO and EPO were efficient in the incorporation of GLA into fish. Compared to the initial day of the experiment, the increase of GLA was significant (from 6.43 to 13.99 and 15.12 mg g^?1, in lipids of fish treated for 30 days with BO and EPO, respectively). The increase of GLA was also observed in fish which were fed with SO diet (6.43–11.43 mg g^?1). Principal component analysis (PCA) allowed the separation of the treatments and discriminated BO and EPO in a group of fish that received the GLA supplemented diet. In addition to GLA, n‐3 fatty acids were important in the characterization of SO diet and affected the separation of BO and EPO from SO in the PCA score plot.     

多重聚合酶链式反应技术检测罗非鱼5种常见食源性致病菌

目的 建立一种可同时检测无乳链球菌(Streptococcus agalactiae)、嗜水气单胞菌(Aeromonas hydrophila)、霍乱弧菌(Vibrio cholerae)、大肠杆菌(Escherichia coli)和沙门菌(Salmonella) 5种罗非鱼常见食源性致病菌的多重聚合酶链式反应(polymerase chain reaction,PCR)方法。方法 根据5种致病菌特异性基因片段设计并合成引物,优化多重PCR体系条件,并对多重PCR体系的特异性、灵敏度以及人工模拟样品进行检测。结果 建立的多重PCR方法可同时扩增5种目的菌株的特异性条带,且不与非靶标细菌发生交叉反应。敏感性实验结果显示,该方法对无乳链球菌、嗜水气单胞菌、沙门菌、霍乱弧菌、大肠杆菌纯培养物基因组DNA的检出限均为0.4 ng/μL。人工模拟样品检测结果显示,该方法可以快速且准确地检测上述5种食源性致病菌,且检出限可达到2×10¹ CFU/g。结论 本研究建立了一种可同时检测无乳链球菌、嗜水气单胞菌、霍乱弧菌、大肠杆菌和沙门菌5种罗非鱼常见食源性致病菌的多重PCR检测...     

仿生波动长鳍运动学建模及算法研究

长鳍波动推进鱼类在稳定性、机动性、低速下状态保持等方面较其它鱼类有着显著优势.本文将鱼类波动 长鳍抽象为零厚度理想波动而,引入直纹面建立曲线坐标意义下波动长鳍的运动学模型,描述了长鳍波动推进时的 非等幅波动、非对称波形等运动特征.面向理论分析和数值模拟,进一步扩充直纹面模型,使之满足弯曲基线、非零 厚度等长鳍形态及运动特征,进而建立筲卡尔坐标系下的长鳍波动描述方程,相应地,设计了鱼类长鳍波动推进的 运动描述算法.根据给定形体和运动参数,对零厚度理想波动板和弓鳍目\"尼罗河魔鬼\"鱼进行运动学仿真,验证 了运动学模型及运动描述算法的有效性.     

Characterization of Mexican Fishes According to Fatty Acid Profile and Fat Nutritional Indices

The fatty acid profile of crevalle jack was compared with that of Atlantic bluefin tuna, Atlantic Spanish mackerel, red snapper, and Nile tilapia. Crevalle jack and Atlantic Spanish mackerel showed similarities in their fatty acid profiles, with the saturated fatty acid > monounsaturated fatty acid > polyunsaturated fatty acid pattern. Atlantic bluefin tuna and red snapper followed a similar pattern to each other, with the polyunsaturated fatty acid > saturated fatty acid > monounsaturated fatty acid pattern, and the pattern for Nile tilapia was saturated fatty acid > monounsaturated fatty acid ≈ polyunsaturated fatty acid. In winter, the DHA+EPA content of crevalle jack (493.2 mg/100 g fillet) was 37% lower than Atlantic bluefin tuna and Atlantic Spanish mackerel, 35% higher than for the red snapper, and 2.8 fold higher than for the Nile tilapia. The best nutritional indices were for Atlantic bluefin tuna > red snapper > Atlantic Spanish mackerel > crevalle jack > Nile tilapia.