Water quality of the river Nile and trace elements of the water, sediments and fish tissues were investigated in the current work. Eighteen different sampling points were selected along the whole course of the River N...Water quality of the river Nile and trace elements of the water, sediments and fish tissues were investigated in the current work. Eighteen different sampling points were selected along the whole course of the River Nile from its spring at Aswan to its estuaries at Rosetta and Damietta. Higher mean value of conductivity, alkalinity, chemical oxygen demand (COD), total organic carbon (TOC), ammonia (NH3), nitrate (NO3), total solid (TS), sulphate (SO4), chloride (Cl), orthophosphate were recorded in the water of Damietta and Rosetta branches comparing to other sites. Also trace metals in the water, sediments and tissues of Clarias gariepinus increased significantly (P Fe > Cu > Pb > Mn > Cr> Cd > Hg. In the gill tissues theses metals were accumulated in the following order Fe > Zn > Mn > Pb > Cr > Cu > Cd> Hg. The low accumulation of metals in muscle may be due to lack of binding affinity of these metals with the proteins of muscle. This is particularly important because muscles contribute the greatest mass of the flesh that is consumed as food.展开更多
从暴发性死亡的革胡子鲶(Clarias gariepinus)中分离出可疑病原菌株2010111403(简称1403),分别采用细菌全细胞脂肪酸鉴定系统、Biolog微生物自动鉴定系统及细菌16 S rDNA序列分析三种方法对其鉴定,结果表明菌株1403为嗜水气单胞菌(Aerom...从暴发性死亡的革胡子鲶(Clarias gariepinus)中分离出可疑病原菌株2010111403(简称1403),分别采用细菌全细胞脂肪酸鉴定系统、Biolog微生物自动鉴定系统及细菌16 S rDNA序列分析三种方法对其鉴定,结果表明菌株1403为嗜水气单胞菌(Aeromonas hydrophila)。分离菌株对健康革胡子鲶致病性测试表明其对革胡子鲶的半数致死剂量(LD50)为6.32×106菌落形成单位(CFU);实验感染革胡子鲶出现与自然发病相似症状,表明菌株1403是引起革胡子鲶发生暴发性死亡的主要致病病原。药敏试验表明,庆大霉素、四环素、阿奇霉素、氟哌酸、先锋霉素等9种抗生素对分离菌株有较强的抑制作用,但分离菌株对复方新诺明、克林霉素、罗红霉素等4种药物表现出耐药性。展开更多
Establishing intraspecific breeding and hybridization programs and determining genetic variability are two important issues for aquaculture. However, interspecific hybridization to improve growth and feeding efficienc...Establishing intraspecific breeding and hybridization programs and determining genetic variability are two important issues for aquaculture. However, interspecific hybridization to improve growth and feeding efficiency is limited. For this purpose, the embryonic and larval development of reciprocal crosses of Clarias gariepinus (Burchell, 1822) and Clarias jaensis (Boulenger, 1909) were studied under laboratory conditions. The fertilization rate varied from 63.33% to 92%, while the hatching rate ranged from 55.68% to 76% with the highest value in hybrids ♀Cg × ♂Cj. Crosses between ♀Cj × ♂Cj, ♀Cg × ♂Cj and ♀Cj × ♂Cg had embryonic stages similar to those of the pure sib ♀Cg x ♂Cg. All crosses, however, had different timing for the various embryological stages. Hatching occurred at 32 h 15 min and 38 h for ♀Cj × ♂Cj and ♀Cj × ♂Cg, and 23 h and 23 h 30 min, respectively, for ♀Cg × ♂Cg and ♀Cg × ♂Cj. However, both crosses produced viable larvae until the first external feeding. The external morphological features of the larvae were completely formed by the 10th day after hatching. The body forms of the crosses at this time were indistinguishable from the pure sib. This study thus laid the groundwork for further comparative studies on hybrid performance and characterization.展开更多
Fishmeal is the most preferred source of protein in aquafeeds, but it is expensive and scarce. Hence, Achatina fulica meat meal (AFM), which is much less preferred for human consumption out of three species of African...Fishmeal is the most preferred source of protein in aquafeeds, but it is expensive and scarce. Hence, Achatina fulica meat meal (AFM), which is much less preferred for human consumption out of three species of African giant land snails, was tested as a fishmeal substitute for Clarias gariepinus growth. Five iso-nitrogenous and iso-calorific diets were formulated, in which AFM substituted fish meal at 0% (control or Diet A), 25% (Diet B), 50% (Diet C), 75% (Diet D) and 100% (Diet E). These dietary treatments were each replicated thrice in a completely randomized design experiment, using 36-L plastic tanks in which the fish were fed daily rations corresponding to 5% of their body weight, for 8 weeks. Water quality parameters in the tanks were monitored. Proximate analyses were conducted on the fish meal, snail meal and experimental diets before the feeding trials. Cost-benefit analysis of the different diets was performed. The crude protein content of AFM (69.18%) was significantly higher than that of fish meal (55.81%). There was no significant difference (P > 0.05) in the mean weight gain, specific growth rate, feed conversion ratio, protein efficiency ratio and survival rate in fish fed Diet A and Diet B. The best protein efficiency ratio (0.77) was recorded in fish fed Diet B. Furthermore, the survival rate of fish increased with increased levels of AFM substitution. Water quality parameters were within a suitable range for tropical fish culture, indicating that the AFM did not pollute the water. The fish fed 25% AFM diet significantly (P Clarias gariepinus diets at a 25% substitution level. The aquaculture industry can thus exploit the availability of this feed resource.展开更多
The response of catfish fed differently timed wet-heat-treated sesame seedmeal was evaluated in the diet of Clarias gariepinus using growth performance, nutrient utilisation and apparent digesti-bility coefficient as ...The response of catfish fed differently timed wet-heat-treated sesame seedmeal was evaluated in the diet of Clarias gariepinus using growth performance, nutrient utilisation and apparent digesti-bility coefficient as indices. Three batches of sesame seed, which were cooked for 10, 20 and 30 minutes, dried, milled, and mechanically defatted using locally made screw press. Each of these differently processed seedmeals was included in the diet of African catfish at varying replacement levels, 15, 30 and 45% with soybean meal. There was good growth performance and nutrient uti-lization by Clarias gariepinus fed with differently timed wet-heat-treated sesame seed that was not significantly different (p > 0.05) from fish fed control diet. More so, the apparent digestibility coef-ficient for organic matter, protein, energy, lipid, fibre, carbohydrate in Clarias gariepinus fed with differently timed wet-heat-treated sesame seedmeal based diets in this study were comparable with the results obtained for fish fed control diets.展开更多
为进一步提高未经漂洗革胡子鲶鱼(Clarias gariepinus,CG)鱼糜的凝胶特性,本试验在CG鱼糜中添加0.4%转谷氨酰胺酶和20 mmol/kg CaCl2基础上(CK组),再依次添加不同浓度的大豆分离蛋白(soybean protein isolation,SPI)、蛋清蛋白(egg whit...为进一步提高未经漂洗革胡子鲶鱼(Clarias gariepinus,CG)鱼糜的凝胶特性,本试验在CG鱼糜中添加0.4%转谷氨酰胺酶和20 mmol/kg CaCl2基础上(CK组),再依次添加不同浓度的大豆分离蛋白(soybean protein isolation,SPI)、蛋清蛋白(egg white protein,EWP)和浓缩乳清蛋白(whey protein concentrate,WPC),SPI添加量分别为CG鱼糜肉重的2%(SPIL)、5%(SPIM)和7%(SPIH),EWP添加量分别记为EWPL(0.1%)、EWPM(0.3%)和EWPH(0.5%),WPC记为WPCL(0.2%)、WPCM(0.4%)和WPCH(0.6%),共制备出10组CG鱼糜凝胶。研究非肌肉蛋白对CG鱼糜的凝胶特性、色泽、持水力、动态流变学性质和微观结构等品质特性的影响。结果表明:整体上非肌肉蛋白的添加会提高CG鱼糜的凝胶特性和TGase活力。其中,SPIL、EWPH和WPCL三组的CG鱼糜凝胶表现出较好的凝胶强度,依次为3322.46、3555.90和4149.31 g·mm,并且网络结构较其他组更紧密、均匀;EWP和WPC的三种添加浓度均会提高CG鱼糜凝胶的白度值;SPI均可使CG鱼糜凝胶的T22向弛豫时间短的方向迁移,其中SPIH组的凝胶持水性(86.64%)最高。动态流变结果表明,三种非肌肉蛋白的添加对CG鱼糜的弹性模量G'和损耗模量G″均产生显著影响,SPIH组、EWPM组和WPCL组为组内最高值。综上分析,在CG鱼糜凝胶中分别添加鱼糜总量的2%SPI、0.5%EWP、0.2%WPC,可显著提高CG鱼糜的凝胶特性。展开更多
文摘Water quality of the river Nile and trace elements of the water, sediments and fish tissues were investigated in the current work. Eighteen different sampling points were selected along the whole course of the River Nile from its spring at Aswan to its estuaries at Rosetta and Damietta. Higher mean value of conductivity, alkalinity, chemical oxygen demand (COD), total organic carbon (TOC), ammonia (NH3), nitrate (NO3), total solid (TS), sulphate (SO4), chloride (Cl), orthophosphate were recorded in the water of Damietta and Rosetta branches comparing to other sites. Also trace metals in the water, sediments and tissues of Clarias gariepinus increased significantly (P Fe > Cu > Pb > Mn > Cr> Cd > Hg. In the gill tissues theses metals were accumulated in the following order Fe > Zn > Mn > Pb > Cr > Cu > Cd> Hg. The low accumulation of metals in muscle may be due to lack of binding affinity of these metals with the proteins of muscle. This is particularly important because muscles contribute the greatest mass of the flesh that is consumed as food.
文摘从暴发性死亡的革胡子鲶(Clarias gariepinus)中分离出可疑病原菌株2010111403(简称1403),分别采用细菌全细胞脂肪酸鉴定系统、Biolog微生物自动鉴定系统及细菌16 S rDNA序列分析三种方法对其鉴定,结果表明菌株1403为嗜水气单胞菌(Aeromonas hydrophila)。分离菌株对健康革胡子鲶致病性测试表明其对革胡子鲶的半数致死剂量(LD50)为6.32×106菌落形成单位(CFU);实验感染革胡子鲶出现与自然发病相似症状,表明菌株1403是引起革胡子鲶发生暴发性死亡的主要致病病原。药敏试验表明,庆大霉素、四环素、阿奇霉素、氟哌酸、先锋霉素等9种抗生素对分离菌株有较强的抑制作用,但分离菌株对复方新诺明、克林霉素、罗红霉素等4种药物表现出耐药性。
文摘Establishing intraspecific breeding and hybridization programs and determining genetic variability are two important issues for aquaculture. However, interspecific hybridization to improve growth and feeding efficiency is limited. For this purpose, the embryonic and larval development of reciprocal crosses of Clarias gariepinus (Burchell, 1822) and Clarias jaensis (Boulenger, 1909) were studied under laboratory conditions. The fertilization rate varied from 63.33% to 92%, while the hatching rate ranged from 55.68% to 76% with the highest value in hybrids ♀Cg × ♂Cj. Crosses between ♀Cj × ♂Cj, ♀Cg × ♂Cj and ♀Cj × ♂Cg had embryonic stages similar to those of the pure sib ♀Cg x ♂Cg. All crosses, however, had different timing for the various embryological stages. Hatching occurred at 32 h 15 min and 38 h for ♀Cj × ♂Cj and ♀Cj × ♂Cg, and 23 h and 23 h 30 min, respectively, for ♀Cg × ♂Cg and ♀Cg × ♂Cj. However, both crosses produced viable larvae until the first external feeding. The external morphological features of the larvae were completely formed by the 10th day after hatching. The body forms of the crosses at this time were indistinguishable from the pure sib. This study thus laid the groundwork for further comparative studies on hybrid performance and characterization.
文摘Fishmeal is the most preferred source of protein in aquafeeds, but it is expensive and scarce. Hence, Achatina fulica meat meal (AFM), which is much less preferred for human consumption out of three species of African giant land snails, was tested as a fishmeal substitute for Clarias gariepinus growth. Five iso-nitrogenous and iso-calorific diets were formulated, in which AFM substituted fish meal at 0% (control or Diet A), 25% (Diet B), 50% (Diet C), 75% (Diet D) and 100% (Diet E). These dietary treatments were each replicated thrice in a completely randomized design experiment, using 36-L plastic tanks in which the fish were fed daily rations corresponding to 5% of their body weight, for 8 weeks. Water quality parameters in the tanks were monitored. Proximate analyses were conducted on the fish meal, snail meal and experimental diets before the feeding trials. Cost-benefit analysis of the different diets was performed. The crude protein content of AFM (69.18%) was significantly higher than that of fish meal (55.81%). There was no significant difference (P > 0.05) in the mean weight gain, specific growth rate, feed conversion ratio, protein efficiency ratio and survival rate in fish fed Diet A and Diet B. The best protein efficiency ratio (0.77) was recorded in fish fed Diet B. Furthermore, the survival rate of fish increased with increased levels of AFM substitution. Water quality parameters were within a suitable range for tropical fish culture, indicating that the AFM did not pollute the water. The fish fed 25% AFM diet significantly (P Clarias gariepinus diets at a 25% substitution level. The aquaculture industry can thus exploit the availability of this feed resource.
文摘The response of catfish fed differently timed wet-heat-treated sesame seedmeal was evaluated in the diet of Clarias gariepinus using growth performance, nutrient utilisation and apparent digesti-bility coefficient as indices. Three batches of sesame seed, which were cooked for 10, 20 and 30 minutes, dried, milled, and mechanically defatted using locally made screw press. Each of these differently processed seedmeals was included in the diet of African catfish at varying replacement levels, 15, 30 and 45% with soybean meal. There was good growth performance and nutrient uti-lization by Clarias gariepinus fed with differently timed wet-heat-treated sesame seed that was not significantly different (p > 0.05) from fish fed control diet. More so, the apparent digestibility coef-ficient for organic matter, protein, energy, lipid, fibre, carbohydrate in Clarias gariepinus fed with differently timed wet-heat-treated sesame seedmeal based diets in this study were comparable with the results obtained for fish fed control diets.
文摘为进一步提高未经漂洗革胡子鲶鱼(Clarias gariepinus,CG)鱼糜的凝胶特性,本试验在CG鱼糜中添加0.4%转谷氨酰胺酶和20 mmol/kg CaCl2基础上(CK组),再依次添加不同浓度的大豆分离蛋白(soybean protein isolation,SPI)、蛋清蛋白(egg white protein,EWP)和浓缩乳清蛋白(whey protein concentrate,WPC),SPI添加量分别为CG鱼糜肉重的2%(SPIL)、5%(SPIM)和7%(SPIH),EWP添加量分别记为EWPL(0.1%)、EWPM(0.3%)和EWPH(0.5%),WPC记为WPCL(0.2%)、WPCM(0.4%)和WPCH(0.6%),共制备出10组CG鱼糜凝胶。研究非肌肉蛋白对CG鱼糜的凝胶特性、色泽、持水力、动态流变学性质和微观结构等品质特性的影响。结果表明:整体上非肌肉蛋白的添加会提高CG鱼糜的凝胶特性和TGase活力。其中,SPIL、EWPH和WPCL三组的CG鱼糜凝胶表现出较好的凝胶强度,依次为3322.46、3555.90和4149.31 g·mm,并且网络结构较其他组更紧密、均匀;EWP和WPC的三种添加浓度均会提高CG鱼糜凝胶的白度值;SPI均可使CG鱼糜凝胶的T22向弛豫时间短的方向迁移,其中SPIH组的凝胶持水性(86.64%)最高。动态流变结果表明,三种非肌肉蛋白的添加对CG鱼糜的弹性模量G'和损耗模量G″均产生显著影响,SPIH组、EWPM组和WPCL组为组内最高值。综上分析,在CG鱼糜凝胶中分别添加鱼糜总量的2%SPI、0.5%EWP、0.2%WPC,可显著提高CG鱼糜的凝胶特性。
