尼罗罗非鱼幼鱼对亚硝酸盐氮长期胁迫的生理功能响应

为了解亚硝酸盐氮长期胁迫下尼罗罗非鱼（Oreochromis niloticus）生理功能变化,实验设置不同浓度亚硝酸盐氮（空白对照、0.03 mmol/L、0.06 mmol/L、0.12 mmol/L、0.23 mmol/L）,研究亚硝酸盐氮21 d胁迫对尼罗罗非鱼幼鱼血液和肝脏组织的生理生化、代谢功能和非特异性免疫的影响。结果表明,随着亚硝酸盐氮的浓度的提高,尼罗罗非鱼幼鱼血液中白细胞数呈现略微上升的趋势,而红细胞数和血红蛋白浓度均呈现显著下降的趋势（P<0.05）;幼鱼血清中,葡萄糖、谷丙转氨酶、谷草转氨酶和K⁺随着亚硝酸盐氮的增加浓度显著提高（P<0.05）,与此同时甘油三酯、总胆固醇、总蛋白、Na⁺和Cl^-浓度、超氧化物歧化酶、碱性磷酸酶、溶菌酶和免疫球蛋白浓度以及亚硝酸盐氮浓度表现出负相关的下降趋势（P<0.05）;肝脏组织中非特异性免疫因子HSP70、IL-1β、IL6和TNF-α随着亚硝酸盐氮的浓度增加表达量显著上升（P<0.05）,而LYS因子表达量则与之相反。研究表明,0.06~0.23 mmol/L亚硝酸盐氮长期胁迫下可导致罗非鱼幼鱼血液生理、代谢和免疫产生功能障碍,并影响肝组织的非特异性免疫基因表达。本研究结果有助于进一步了解亚硝酸根离子在罗非鱼体内的毒性机制,为建立罗非鱼养殖水质亚硝酸盐氮因子的安全阈值提供参考。     

氨氮与拥挤胁迫对吉富品系尼罗罗非鱼幼鱼生长和肝脏抗氧化指标的联合影响

采用中心复合试验设计(CCD)和响应曲面方法(response surface methodology,RSM),探讨了氨氮(0.02 ～ 2.00 mg/L)和养殖密度(1～5尾/10 L)对吉富罗非鱼幼鱼生长和肝脏抗氧化指标的联合影响.结果表明,本试验条件下,氨氮和养殖密度的一次与二次效应对特定生长率有显著影响(P＜0.05),随着氨氮或养殖密度的上升,特定生长率呈先上升后下降的变化.氨氮与养殖密度之间存在互作效应(P＜0.05),氨氮浓度为0.02 ～0.20 mg/L,养殖密度在1～2尾/10 L时,幼鱼特定生长率较高;而氨氮浓度高于0.20 mg/L,养殖密度在3尾/10 L左右时,生长速度较快.肝脏丙二醛(MDA)含量随氨氮浓度和养殖密度的上升而上升,超氧化物歧化酶(SOD)和过氧化氢酶(CAT)的活力呈先上升后下降的变化.氨氮与养殖密度的一次效应对MDA含量和两种酶活力均有显著影响(P＜0.05),二次效应对两种酶活力的表达有极显著影响(P＜0.01);氨氮与养殖密度对CAT活力有互作效应,高浓度氨氮与高养殖密度环境会抑制SOD和CAT活力的表达.因子与响应值间二次多项回归方程的决定系数分别达到0.972 4、0.913 2、0.938 9和0.969 2(P＜0.01),可用于预测;氨氮效应对生长和抗氧化酶活力的影响较养殖密度明显.建议在罗非鱼的养殖过程中合理安排好养殖密度,保持溶氧充足,降低氨氮胁迫,提高罗非鱼的生长与抗病力.     

饲料中添加木聚糖酶对尼罗罗非鱼生长及血清激素水平的影响

以尼罗罗非鱼(Tilapia nilotica)为实验对象,初始体质量为(106.16±16.77)g,以小麦基础饲料为对照,小麦基础饲料中分别添加不同质量百分比水平的木聚糖酶(0.05%、0.10%、0.15%)作为实验饲料。每个处理设5个重复,每个重复放养40尾雄性罗非鱼。采用饱食方式饲喂75 d后测定罗非鱼体质量、血清胃泌素(Gas)、三碘甲腺原氨酸(T3)、甲状腺素(T4)、胰岛素(Ins)、胰高血糖素(Glu)和类胰岛素样生长因子-Ⅰ(IGF-Ⅰ)的含量。结果表明:0.05%和0.10%木聚糖酶添加组的增重率较对照组分别提高8.29%、17.45%(P<0.01),0.15%组的增重率与对照组相比没有统计学差异(P>0.05)。0.05%组、0.10%组、0.15%组的血清Gas水平分别比对照组提高22.55%(P>0.05)、88.46%(P<0.01)和167.84%(P<0.01);0.10%组和0.15%组血清中T3水平极显著高于对照组(P<0.01),0.05%组T3水平与对照组无显著差异,0.05%组、0.10%组和0.15%组的血清T4水平分别比对照组提高42.36%、65.66%和68.58%(P<0.01);0.05%组、0.10%组和0.15%组的血清Ins水平有极显著差异(P<0.01),并分别比对照组提高54.95%、73.42%和36.04%(P<0.01),其Ins水平从大到小依次为:0.10%组、0.05%组、0.15%组;0.05%组、0.10%组、0.15%组的血清Glu含量分别比对照组降低11.59%、17.15%和13.31%(P<0.01),0.10%组的血清Glu水平极显著低于0.05%组和0.15%组(P<0.01);0.05%组、0.10%组、0.15%组的血清IGF-I水平分别比对照组提高75.57%、102.46%、39.96%(P<0.01)。因此,本研究认为,在小麦基础饲料中适量添加木聚糖酶可以调控尼罗罗非鱼内分泌系统,调节血清激素水平,促进尼罗罗非鱼生长。     

饥饿胁迫对吉富罗非鱼生长及生理生化指标的影响

实验选取90吉富罗非鱼(GIFT,Oreochromis niloticus),平均体质量137.18 g,随机分为6个平行组,饥饿处理0 d、7 d、14 d、21 d,测定饥饿对鱼体的生长、血液生化指标、应激蛋白HSP70基因表达以及鱼体组成的影响,结果表明,饥饿0～21 d过程中,随着饥饿时间的延长,鱼体体质量、内脏质量、肝体比、内脏比、血清甘油三酯、血清一氧化氮浓度、血清超氧化物歧化酶活性、肝脏HSP70的mRNA水平、鱼体能量、肌肉粗脂肪、肝脏灰份、肠系膜脂肪含量等指标呈现下降的趋势,而血清丙二醛浓度呈现增加趋势,并且与饥饿前相比在饥饿21 d时有显著性差异(P<0.05).血清皮质醇与总蛋白浓度呈现先增加后降低趋势,并且与饥饿前相比在饥饿7 d时有显著性差异.饥饿0～21d过程中,鱼体肌肉水份、肝脏水份、肌肉粗蛋白、肝脏粗蛋白与粗脂肪等含量没有较大的变化.因此饥饿时吉富罗非鱼先动用体内储存的脂肪来满足鱼体需要,长期的饥饿有可能降低鱼体免疫与抗氧化能力,直接影响鱼体健康.     

温度与盐度对吉富品系尼罗罗非鱼仔鱼生长与存活的联合影响

采用中心复合实验设计(CCD)和响应曲面方法(response surface methodology,RSM),探讨了温度(18～37℃)和盐度(0～16)对吉富品系尼罗罗非鱼(Oreochromis miloticus)仔鱼生长和存活的联合影响.结果表明,本实验条件下,温度与盐度的一次与二次效应对特定生长率和存活率均有显著影响(P＜0.05),随着温度或盐度的上升,生长与存活均呈先上升后下降的变化.温度与盐度间存在互作效应(P＜0.05),温度为18～20℃时,仔鱼的特定生长率与存活率在盐度为8～9时较高;随着温度上升,27～32℃时,盐度为5～7时较高;高温环境时(35～37℃),盐度在4左右,生长与存活率较高.所考察因子与生长和存活率间的二次多项回归方程的决定系数分别达到0.979 6和0.982 l(P＜0.01),可用于预测罗非鱼的生长与存活率;温度效应对生长的影响较盐度明显,而对存活率的影响则相反.通过对所建立的两个回归方程同时优化,得到2个因子的最佳组合为:温度29.1℃和盐度5.4,在此最佳因子组合下罗非鱼仔鱼的特定生长率与存活率达到最优,分别为10.08％.d-1和91.34％,其可靠性达0.973.建议罗非鱼仔鱼在本研究中得到的最优因子组合下进行培育,以提高生产效率.     

不同盐度对尼罗罗非鱼存活和生长性能的影响

为评估选育耐盐尼罗罗非鱼(Oreochromis niloticus)在高盐度水体中的生长性能,在塑料盒(80cm×60cm×60cm)中设置盐度21‰、24‰、27‰和29‰共四个盐度梯度处理进行耐盐鱼苗的生长性能比较研究。养殖40d的生长结果表明,随着盐度的逐步增加,选育尼罗罗非鱼苗存活率呈明显下降的趋势,且日增重、增重率以及特定生长率等指标也均呈下降趋势。耐盐选育尼罗罗非鱼可以在29‰的盐度下正常生长,且存活率可达80%以上,本试验为尼罗罗非鱼在半咸水地区养殖提供基础数据。     

两种乳酸菌对尼罗罗非鱼生长及免疫性能的影响

为研究饲料中添加植物乳杆菌(Lactobacillus plantarum)LP-37与戊糖片球菌(Pediococcus pentosaceus) PP-23对尼罗罗非鱼(Oreochromis niloticus)生长及免疫性能的影响,试验共分为7组:对照组C0,投喂基础饲料;L1-L3组,在基础饲料中添加不同浓度(1.0×10⁶ CFU/g、1.0×10⁷ CFU/g、1.0×10⁸ CFU/g)植物乳杆菌LP-37;P1-P3组,在基础饲料中添加不同浓度(1.0×10⁶ CFU/g、1.0×10⁷ CFU/g、1.0×10⁸ CFU/g)戊糖片球菌PP-23。结果表明:除L1组外,其余试验组末均重(123.22～158.60) g较C0组(118.16±4.88) g均显著增高(P<0.05);除L1组与P1组外,其余试验组增重率(128.69%～156.20%)较C0组(108.16±0.45)%均显著提高(P<0.05),L3与P2...     

3种品系尼罗罗非鱼(Oreochromis niloticus)盐碱耐受性和生长比较

为评估尼罗罗非鱼的耐盐碱性能,分别测定了上海、山东、河北3种品系尼罗罗非鱼鱼种96 h的半致死盐、碱度,并在不同盐碱混合浓度(S0A0、S10A0、S10A2、S10A4、S10A6)中进行为期60 d的养殖生长比较。单盐、单碱耐性研究表明,上海、山东、河北3种品系尼罗罗非鱼鱼种的96 h半致死盐度分别为18.528 g/L、20.347 g/L、19.342 g/L,96 h半致死Na HCO3碱度为8.827g/L、8.540 g/L、8.542 g/L。盐碱混合条件下,盐度为10时,96 h半致死碱度分别为河北品系(4.377g/L)上海品系(3.561 g/L)山东品系(3.108 g/L),品系之间差异显著(P0.05);盐度为15时,96 h半致死碱度分别为河北品系2.144 g/L,上海品系2.183 g/L,山东品系2.183 g/L,品系之间无显著差异(P0.05),高盐度下尼罗罗非鱼鱼种的碱度耐受性明显低于低盐度下的碱度耐受性。结果表明,尼罗罗非鱼日均增重率在S0A0、S10A0组间无显著差异(P0.05),随着盐碱浓度增加,盐碱S10A4和S10A6组中日均增重率呈下降趋势,河北品系表现出相对生长优势(P0.05)。研究结果为尼罗罗非鱼适宜养殖的盐碱范围的确定、耐盐碱品系的筛选提供了基础资料。     

池塘循环水槽养殖模式下吉富罗非鱼的生长及生理响应变化

为探讨在池塘循环水槽养殖模式下吉富罗非鱼不同养殖密度的生长特性和生理指标变化,评估吉富罗非鱼在池塘循环水槽养殖模式下的适宜养殖密度,以吉富罗非鱼为实验对象,设计传统池塘养殖模式放养密度5尾/m² (SD1组),池塘循环水槽养殖模式放养密度180尾/m² (SD2组)和270尾/m² (SD3组),比较各组吉富罗非鱼的生长性能,分析血液生化指标和肝脏HSP70 mRNA表达量的变化规律。结果显示,经过120 d的养殖,SD2组吉富罗非鱼终末体质量、特定生长率和绝对生长率显著高于SD1和SD3组。SD2和SD3组存活率、体质量差异系数和饵料系数低于SD1组。SD2组血清皮质醇、血清谷丙转氨酶、谷草转氨酶、溶菌酶水平和肝脏HSP70 mRNA的相对表达量在30 d时显著高于SD1组。SD3组血清皮质醇和葡萄糖水平在60 d后持续上升,120 d时显著高于SD1组,谷丙转氨酶、谷草转氨酶、溶菌酶水平和肝脏HSP70 mRNA的相对表达量在60、90 d时显著高于SD1组,甘油三酯在整个实验期显著低于SD1组。SD2组吉富罗非鱼在...     

海豚链球菌感染对不同品系罗非鱼血液生化指标和肝脏HSP70 mRNA表达的影响

以吉富罗非鱼、新吉富罗非鱼、埃及尼罗罗非鱼和红罗非鱼为研究对象,饲养100d后,进行海豚链球菌(2.95×108CFU/mL)感染试验,分析攻毒前后各品系罗非鱼的血液生化指标和肝脏HSP70 mRNA表达量的变化规律。另从各桶中取20尾鱼进行同样的攻毒试验,统计攻毒后各时间点的累积死亡率。结果表明,感染海豚链球菌96h后,吉富罗非鱼和新吉富罗非鱼对病原较为敏感,累积死亡率分别达到36.67%和38.33%;埃及尼罗罗非鱼对病原敏感性较差,试验期间未见死亡。吉富罗非鱼、新吉富罗非鱼和红罗非鱼血清皮质醇和葡萄糖水平以及肝脏HSP70 mRNA的表达量在攻毒后明显提高,血清谷丙转氨酶、谷草转氨酶与溶菌酶活力也呈上升趋势,碱性磷酸酶活力与甘油三酯和胆固醇水平低于攻毒前。埃及尼罗罗非鱼可以利用糖原和脂类产生的能量,提高了HSPS与一些特定免疫蛋白(溶菌酶、球蛋白等)的合成,增强了鱼体的非特异性免疫力。罗非鱼选育过程中,需要将抗病力与生长性能进行有效的结合,在注重生长速度的同时也要增强其抗应激能力,从而为罗非鱼产业的可持续发展提供保证。     

Effect of stocking density on the growth performance and yield of Nile tilapia [Oreochromis niloticus (L., 1758)] in a cage culture system in Lake Kuriftu,Ethiopia

This research was conducted to investigate the effect of stocking density on the growth performance and yield of Oreochromis niloticus in cage culture in Lake Kuriftu. The treatments had stocking densities of 50 (50F), 100 (100F), 150 (150F), and 200 (200F) fish per m^?3. All treatments were in duplicate. Juveniles with an average weight of 45. 76±0.25 g were stocked in the treatments. The fish were fed a composite mixture of mill sweeping, cotton seed, and Bora food complex at 2% of their body weight twice per day using feeding trays for 150 days in powdered form. The growth performance of O. niloticus was density dependent. The final mean weight of O. niloticus ranged 147.76±0.28–219.71±1.42 g and the mean daily weight gain was 0.69±0.01–1.15±0.02 g day^?1. Fish held in cages with lower density were heavier than the ones held at higher densities, and showed higher weight gain and daily weight gain. The most effective stocking density, in terms of growth parameters, was 50 fish m^?3. The gross yield (4.5–20.55 kg cage^?1) showed a significant difference with increasing stocking density (P<0.05). Moreover, the apparent food conversion ratio (2.48–7.22) was significantly affected by stocking density (P<0.05). However, survival rate was not affected by stocking density (P>0.05). It can be concluded that the most effective stocking densities were at 50 fish m^?3 cage for larger size fish demand in a short period and 200 fish m^?3 for higher gross production with supplementary feed.     

Increased spawning activity of female Nile tilapia (Oreochromis niloticus) (L.) after stocking density and photoperiod manipulation

This study was conducted to evaluate the effects of stocking density and photoperiod in increasing the reproductive performance of Oreochromis niloticus. In experiment 1, a change in stocking density (from 47.7 to 6.8 kg m^?3) was performed, with groups of 48 females moved to single compartments. In experiment 2, 36 females experienced a 6L:18D photoperiod for 21 or 28 days (stocking density: 31.3 kg m^?3) before being placed in individual compartments (stocking density of 6.9 kg m^?3, 12L:12D photoperiod). The spawning rates in experiment 1 (32.2%) and in experiment 2 (21 days: 65.2%, 28 days: 36.1%) were significantly higher than those in the control (17.7%). On the other hand, hatching and swim‐up fry rates were significantly lower in experiment 2 – 21 days (41.3%, 40.4%) but not in experiment 1 (64.0%, 56.3%) compared with the control (67.0%, 62.3%). The spawning rate in experiment 2 – 21‐day treatment group was the highest, while the number of eggs collected per female was significantly lower than that in the control. In experiments 1 (20.8%) and 2 (21 days: 44.4%, 28 days: 19.4%), the daily spawning rates were the highest 3 days after maintaining females in single compartments. The current experiment demonstrates how specific stocking density changes can be used to induce higher spawning rates in Nile tilapia.     

Effects of stocking density on growth, yield and profitability of farming Nile tilapia, Oreochromis niloticus L., fed Azolla diet, in earthen ponds

Two consecutive experiments were conducted to study the effects of stocking density on growth, food utilization, production and farming profitability of Nile tilapia (Oreochromis niloticus) fingerlings (initial mean weight: 16.2 ± 0.2 g) fed Azolla, as a main component in diet. In experiment 1, fish were hand‐fed twice daily with three isonitrogenous (28.5% crude protein) and isocaloric (14.5 kJ g⁻¹) diets A30, A35 and A40 containing 30%, 35% and 40%Azolla, respectively, for 90 days. Diets were formulated by mixing Azolla with locally available by‐products. No significant differences were found in growth parameters and production (P>0.05). Total investment cost was significantly higher with A30 (P<0.05), but same profitability values were obtained with all diets (P>0.05). In experiment 2, three stocking densities, 1, 3 and 5 m⁻², were assigned to three treatments T₁, T₂ and T₃ respectively. Fish were hand‐fed twice daily with diet A40. The final mean weight (89.53–115.12 g), the mean weight gain (0.81–1.10 g day⁻¹), the specific growth rate (1.90–2.20% day⁻¹) and the apparent food conversion ratio (1.29–1.58) were affected by stocking density, with significant difference (P<0.05) at 5 m⁻², compared with the other densities. Stocking density did not affect survival rate (P>0.05). Yield and annual production increased with increasing stocking density, ranging from 7.10 ± 0.90 to 25.01 ± 1.84 kg are⁻¹ and 28.79 ± 3.66 to 101.42 ± 7.48 kg are⁻¹ year⁻¹, respectively, with significant differences between all densities (P<0.05). Higher stocking density resulted in higher gross return and lower cost of fish production, with significant variations (P<0.05). The net return increased with increasing stocking density (P<0.05). However, both densities of 3 and 5 m⁻² produced the same profitability values. On the basis of growth values and economic return, it was concluded that Nile tilapia could be raised at a density of 3 fish m⁻² with A40 to improve production and generate profit for nutritional security and poverty alleviation in rural areas.     

Effects of stocking density on growth performance and welfare‐related physiological parameters of Atlantic salmon Salmo salar L. in recirculating aquaculture system

Stocking density, representing a potential source of long‐term stress, is widely recognized as a critical factor in aquaculture husbandry. Atlantic salmon were reared at low‐density (LSD, ~9.80–18.41 kg m^?3, initial to final density), medium‐density (MSD, ~19.62–36.96 kg m^?3) and high‐density (HSD, ~28.79–53.54 kg m^?3) stocking levels for 66 days to investigate the stress‐induced changes in fish growth and welfare. At the end of the trial, the salmon in HSD group showed significant lower final weight and higher ration level than those in MSD and LSD groups (P < 0.05). The salmon farmed in LSD group had higher special growth rate (SGR) and lower feed conversion ratio (FCR) (P < 0.05). However, stocking density could not affect the mortality, condition factor and coefficient of variation of salmon. The pectoral fin index of salmon in LSD group was significantly higher than that in HSD group (P < 0.05). Fifteen haematological and serum parameters were detected to assess the stress and welfare levels of salmon. The salmon farmed in HSD group had higher glucose (GLU) level and lower Cl^?, haemoglobin (HGB) and red blood cell (RBC) concentrations (P < 0.05). Contrast to the pattern of superoxide dismutase (SOD) activity, the cortisol, maleic dialdehyde (MDA) and alkaline phosphatase (ALP) levels of HSD group were higher than those in other two groups (P < 0.05). All these findings will provide a reference for selecting suitable stocking density in Atlantic salmon farming industry.     

Comparative study of growth performance of three strains of Nile tilapia, Oreochromis niloticus, L. at two stocking densities

This study was conducted to investigate the effect of stocking density (125 or 200 fish m^?3) on the growth performance of three strains of the Nile tilapia, Oreochromis niloticus: the non‐improved strain (NS), the genetically improved farmed tilapia (GIFT) and the Freshwater Aquaculture Center selected tilapia known as the FaST selected line (SL). Each strain and density combination was triplicated in 0.42 m³ fibreglass tanks within a re‐circulating water system. Water temperature was maintained at 29.0±1.0°C. Large Nile tilapia having a mean body weight of 100–110 g were stocked in each tank and hand‐fed four times daily with commercial tilapia pellets (35% protein) for 104 days. Results showed that at the two stocking densities, the GIFT and SL strains showed a significantly higher (P<0.05) mean weight (MWT), daily growth rate (DGR), specific growth rate (SGR), feed conversion ratio (FCR) and gross yield (GY) than the NS. In all three strains, growth performance was negatively affected by stocking density. The lower density (125 fish m^?3) treatments had significantly higher MWT, DGR and SGR than the higher density one (200 fish m^?3). However, higher FCR and GY were observed at the higher density. Survival rates were high in all treatments and were not affected by strain or density. In general, the SL strain had better growth parameters than the GIFT strain. The findings of this study demonstrated the superior growth performance of the improved strains at both densities compared with the NS. The higher density (200 fish m^?3) could be more profitable for the tilapia farms in Kuwait than the lower density of (125 fish m^?3) in terms of reduced land cost and facilities, demand on the limited low‐salinity underground water and manpower.     

Physiological responses and HSP70 mRNA expression of GIFT strain of Nile tilapia (Oreochromis niloticus) under cold stress

An investigation on the physiological responses and HSP70 expression under cold stress was conducted on Genetically Improved Farmed Tilapia (GIFT) strain of Nile tilapia (Oreochromis niloticus). Tilapia were acclimated at 28°C as control and then the water temperature was reduced from 28°C to 15°C at a rate of 1°C h^?1, and serum biochemical indices, antioxidant enzymes and expression of HSP70 mRNA were analysed on days 0, 0.5, 1, 2, 3 and 5 after exposure to 15°C. The concentration of serum K, Na, Cl and Ca concentration showed instability during cold stress. Glucose rapidly increased on day 0 followed by a declining trend. Triglyceride, cholesterol, low density lipoprotein‐cholesterol signifi‐cantly decreased and high density lipoprotein‐cholesterol showed instability during cold stress. Aspartate aminotransferase, alanine aminotransferase and lactate dehydrogenase activities were prominently elevated under cold stress. Superoxide dismutase and catalase activities showed a remarkable rise on day 0.5 under cold stress, and gradually decreased thereafter. HSP70 mRNA level significantly increased both in liver and muscle under cold stress, especially on days 0.5 and 1. These results suggest that cold influences several physiological responses of tilapia, and the cold resistance and cold tolerance of tilapia will benefit from the enhancement of antioxidant enzymes activities and upregulated HSP70 mRNA expression.     

养殖密度对鱼类福利影响的研究进展I．死亡率、生长、摄食以及应激反应

养殖密度影响鱼类福利是鱼类生理生态学、福利学和种群生态学研究中的关键问题,已受到各国学者的关注。文章综述了养殖密度影响鱼类福利的主要研究进展,讨论了鱼类死亡率、生长、摄食以及应激反应等福利指标随养殖密度变化的规律及其描述方法；在此基础上,对鱼类福利指标随不同放养密度变化规律的研究以及应用前景进行了展望。     

Effect of dietary conjugated linoleic acid levels on growth performance,muscle fatty acid profile,hepatic intermediary metabolism and antioxidant responses in genetically improved farmed Tilapia strain of Nile tilapia Oreochromis niloticus

An 8‐week feeding trial was conducted to determine the effect of dietary conjugated linoleic acid (CLA) on growth performance, muscle fatty acid profile, hepatic intermediary metabolism and antioxidant responses in genetically improved farmed Tilapia (GIFT) strain of Oreochromis niloticus (initial body weight: 42.6 ± 0.4 g, mean ± standard deviation). Three replicated groups of GIFT strain of Nile tilapia were hand‐fed to satiation, twice a day, with the diets in which CLA oil, containing mainly the bioactive cis‐9, trans‐11 and trans‐10, cis‐12 isomers, was included at 0 (control), 0.5%, 1%, 1.5%, 2% and 2.5%, respectively, at the expense of fish oil to maintain the constant lipid and energy levels. Growth performance and feed utilization showed no significant differences among the treatments (P > 0.05). The dietary inclusion of CLA modified total percentages of the main groups of fatty acids. Increasing saturated fatty acid content and reduced mono‐unsaturated fatty acid contents in muscle were observed with increasing dietary CLA inclusion (P < 0.05). Total n‐3 fatty acids and total polyunsaturated fatty acids tended to decline with increasing dietary CLA levels (P < 0.05), but n‐6 fatty acids showed no significant differences among the treatments (P > 0.05). Dietary CLA supplementation resulted in the significant increase in the trans‐10, cis‐12 and cis‐9, trans‐11 CLA isomers in muscle (P < 0.05) and also significantly influenced several hepatic enzymatic activities, such as succinate dehydrogenase, lactate dehydrogenase, malic dehydrogenase, lipoprotein lipase and hepatic lipase activities (P < 0.05). Reduced superoxide dismutase and glutathione peroxidase activities, and the decline in malondialdehyde levels were observed in fish fed the CLA‐supplemented diets (P < 0.05), indicating that dietary CLA supplementation showed a powerful antioxidant effect for this fish species. Our study was the first report involved in the effect of dietary CLA inclusion on hepatic intermediary metabolism and antioxidant responses in fish, which could be used as indicators of nutritional and physiological status of the fish species.     

Effects of stocking density and feeding levels on growth and feed efficiency of Nile tilapia (Oreochromis niloticus L.) fry

The effects of stocking density and feeding levels on larval survival, growth rates, feed utilization efficiency and body composition of Nile tilapia (Oreochromis niloticus L.) fry were investigated in two consecutive experiments. In experiment 1, swimup fry (0.016 g average body weight) were stocked in 20‐L fibreglass tanks, in a closed, recirculating indoor system, at five stocking densities (3, 5, 10, 15 and 20 fry L^?1) and fed a larval test diet (40% crude protein) to apparent satiation, three times a day, for 40 days. Fish survival, percentage weight gain and specific growth rate (% SGR) were negatively correlated with stocking density. The best performance was achieved at 3 fry L^?1. However, no significant differences in growth parameters were found between 3 and 5 fry L^?1. Body composition was not significantly affected by stocking density. In experiment 2, fry (0.016 g average body weight) were stocked at 5 fry L^?1, and fed a larval test diet (40% crude protein) at six feeding levels (10%, 20%, 25%, 30% and 35% BW day^?1) and to satiation, three times a day for 40 days. Fish growth rates and survival were extremely poor at 10% feeding level, and improved significantly with increasing feeding levels up to 30%, and levelled off with further increase in feeding levels. On the contrary, feed conversion ratio (FCR) and protein production value (PPV) were negatively correlated with feeding level. The lowest feeding level (10%) produced significantly lower body lipid and higher protein and ash than other feeding levels. The present results suggest that the optimum stocking density and feeding level of Nile tilapia fry are 5 fry L^?1 and 30% per day respectively.     

饲料中海洋红酵母对尼罗罗非鱼幼鱼生长性能、消化酶及免疫酶活性的影响

为了研究海洋红酵母(Rhodotorula mucilaginosa)对尼罗罗非鱼(Oreochromis niloticus)幼鱼生长性能、消化酶及免疫酶活性的影响,配制6组饲料,分别为对照组、添加1 gkg-1、2 gkg-1、3 gkg-1、4 gkg-1和5 gkg-1的海洋红酵母组,投喂初始均质量为(5.220.01) g的尼罗罗非鱼,实验56 d。结果显示,与对照组相比,2 gkg-1和4 gkg-1组的饲料系数显著降低(P0.05),1 gkg-1、3 gkg -1和5 gkg-1组则没有显著性差异(P0.05)。5 gkg-1组鱼体粗蛋白含量显著低于1 gkg-1和2 gkg-1组(P0.05),1 gkg-1、3 gkg-1和5 gkg-1组鱼体粗灰分含量显著低于对照组(P0.05)。与对照组相比,1 gkg-1组胃蛋白酶活性显著升高(P0.05),3 gkg-1、4 gkg-1和5 gkg-1组胃蛋白酶活性显著降低(P0.05)。2 gkg-1和3 gkg-1组前肠和中肠淀粉酶和脂肪酶,以及肝脏溶菌酶和一氧化氮合酶活性均显著高于对照组(P0.05)。根据尼罗罗非鱼幼鱼的消化酶和免疫酶活性等指标综合分析得出,海洋红酵母在罗非鱼饲料中的建议添加量为2～3 gkg-1。