Dietary Zinc Requirement of Oreochromis aureus and Effects of Dietary Calcium and Phytate on Zinc Bioavailability

Two experiments were conducted to determine the dietary zinc requirement of fingerling blue tilapia ( Oreochromis oureus ) and the effects of dietary calcium and phytate on zinc bioavailability. Purified egg white diets containing graded levels of supplemental zinc were fed to fingerling tilapia in triplicate aquaria for 80 days. No overt signs of zinc deficiency were observed; however, scale and bone zinc concentrations of fish fed the various diets were significantly (P < 0.05) affected and increased linearly as dietary zinc increased until plateauing at 20 mg Zn/kg diet and greater. Based on these data, 20 mg Zn/kg of dry diet was determined to be the minimum dietary zinc requirement of blue tilapia. Purified egg white diets containing 20 mg Zn/kg were also supplemented with 0.5 or 2.0% calcium and 0 or 1.5% phytate in a factorial arrangement to determine the effects of these dietary factors on zinc bioavailability. At this level of supplemental zinc, 1.5% phytate significantly ( P < 0.05) reduced zinc bioavailability as reflected in scale and bone zinc concentrations; whereas, dietary calcium did not affect zinc bioavailability. Results from this study establish the dietary zinc requirement of blue tilapia and indicate that higher levels of supplemental zinc should be included in practical feeds to compensate for reduced zinc bioavailability caused by dietary phytate.     

Evaluation of the Dietary Zinc Requirement of Penaeus vannamei and Effects of Phytic Acid on Zinc and Phosphorus Bioavailability

Experiments were conducted to determine the dietary zinc requirement of Penaeus vannomri and evaluate the effects of phytate on zinc bioavailability. Prior to initiation of the growth trial, 20-day-old P. vonnamei postlarvae (mean weight 0.0032 g) were fed a casein-gelatin based semi-purified diet lacking zinc supplementation but containing 18 mg Zn/kg diet for one week. Subsequently, juveniles (mean weight 0.058 g) were fed one of seven diets containing either supplemental zinc (0, 15, 30, 60 mg/kg diet) without phytate or supplemental zinc (0, 60, 200 mg/kg diet) with 1.5% phytate for 33 days. Weight gain was greatest in shrimp fed 15 mg supplemental Zn/kg diet. In the absence of dietary phytate, zinc concentrations in the hepatopancreas of shrimp were maximized when zinc was supplemented at levels greater than or equal to 15 mg Zn/kg diet (33 mg total Zn/ kg). Supplementation of 1.5% phytate to the diet did not have a significant effect on growth or zinc concentrations in the carapace; however, it did depress zinc levels in the hepatopancreas. Supplementation of 200 mg Zn/kg diet was required to overcome the depressed bioavailability of zinc caused by the presence of dietary phytate and return zinc levels of the hepatopancreas to that observed when phytate was not present. Based on apparent digestibility values phytate phosphorus was unavailable to the shrimp and the presence of phytate depressed the bioavailability of phosphorus and zinc.     

Effects of Dietary Magnesium on Growth and Tissue Magnesium Content of Blue Tilapia Oreochromis aureus

Juvenile blue tilapia Oreochrornis aureus (mean weight 0.5 ± 0.05 g) were stocked into 38 liter glass aquaria receiving Row-through well water containing 0.1 mg magnesium/L and fed semipurified, casein-based diets containing graded levels of magnesium (0.003, 0.008, 0.023, 0.037, 0.050 and 0.065% magnesium, dry weight). Magnesium supplements were provided as anhydrous magnesium sulfate (MgSO₄). No treatment-related mortalities occurred and no visible magnesium deficiency symptoms were observed in any treatment group during the 18 week experimental period. Magnesium concentrations in scale and bone of tilapia fed diets containing 0.023 to 0.065% magnesium were greater ( P < 0.05) than in fish fed diets containing 0.003 to 0.008%. Scale and bone magnesium concentrations did not differ ( P > 0.05) among fish that received dietary magnesium levels of 0.023% or greater. The magnesium content of muscle was higher ( P < 0.05) in fish fed 0.037 to 0.065% magnesium than in those fed 0.003 to 0.008% magnesium. Muscle magnesium concentrations did not differ ( P > 0.05) among fish that received 0.037% or more dietary magnesium. Adequate weight gain and superior feed efficiency occurred in fish fed 0.05 to 0.065% magnesium. Results indicated that diets for O. aureus should contain at least 0.05% magnesium (500 mg Mg/kg dry diet) for optimum growth and normal tissue mineralization.     

Dietary Zinc Requirement of Hybrid Striped Bass,Morone chrysops×Morone saxatilis,and Bioavailability of Two Chemically Different Zinc Compounds

Zinc is a trace mineral element that plays an essential role in numerous biochemical processes, and has been shown to affect growth and health of several fish species. However, the dietary zinc requirement of hybrid striped bass has not been defined. Therefore, a feeding trial was conducted to determine the dietary requirement for zinc by this fish and to compare zinc bioavailability of two chemically different forms (zinc sulfate and zinc proteinate). Six experimental diets were formulated with purified ingredients and supplemented with ZnSO₄ to provide total zinc concentrations of 7, 12, 16, 26, 42, and 80 mg/kg diet which were determined by analysis. Each diet contained 32% crude protein, 6% lipid, and approximately 14.2 kJ of digestible energy per gram. The experimental diets were fed twice daily for 10 wk to triplicate groups of 15 hybrid striped bass initially weighing 0.86 ± 0.05 g/fish in 38‐L glass aquaria, connected as a recirculating system. Finally, after the feeding period, the fish were evaluated for weight gain, feed efficiency, protein efficiency ratio, and survival, as well as blood serum zinc, bone zinc, and hematocrit. All fish thrived during the feeding trial and not even the fish fed the basal diet displayed any apparent deficiency signs, although weight gain steadily increased with escalating levels of dietary zinc up to 42 mg/kg diet. On the basis of the most responsive indicators–bone zinc and serum zinc–the minimum dietary zinc requirement of hybrid striped bass was determined to be 17.0 and 17.3 mg Zn/kg diet, respectively, based on broken‐line regression. This estimate is similar in magnitude to dietary zinc requirements reported for other fish species. In addition, the bioavailability of zinc proteinate versus that of ZnSO₄ was estimated by deriving the ratio of the slopes of the regression lines fitted to bone zinc and serum zinc data. This analysis indicated that hybrid striped bass utilized zinc proteinate ～1.7 times more efficiently than ZnSO₄.     

Dietary calcium and phosphorus requirements of Oreochromis aureus reared in calcium-free water

Two experiments were conducted to evaluate the dietary calcium and phosphorus requirements of fingerling Oreochromis aureus reared in calcium-free water. A casein basal diet was supplemented with graded levels of either calcium or phosphorus and fed for 12 weeks. Dietary calcium concentrations ranged from 0.17 to 1.00% and dietary phosphorus concentrations ranged from 0.20 to 1.00%. Weight gain and feed conversion data indicated that 0.70% dietary calcium was optimum for good growth. Whole-body, bone or scale minerals did not clearly reflect the calcium requirement as established by growth. Weight gain and feed conversion data indicated that 0.30% dietary phosphorus was adequate for good growth. However, bone ash, phosphorus, and calcium data indicated that 0.50% dietary phosphorus was required for normal bone mineralization.     

尼罗与奥利亚罗非鱼对池塘蓝藻水华及水质影响的研究

利用尼罗罗非鱼和奥利亚罗非鱼进行了池塘抑藻试验,采用血球计数板测定水体中的微囊藻密度,并对水体理化性质进行了检测分析。试验结果表明,罗非鱼能有效消减水体中蓝藻生物量,降低水体藻毒素浓度,并对水体TN、TP产生一定影响。其中奥利亚罗非鱼试验组蓝藻初始密度为1．53-108cells／L,下降至0．86-108eells／L,降低43．79％;尼罗罗非鱼组蓝藻初始密度为1．54-108cells／L,下降至O．51×108cells,L,降低66．88％。水体总磷含量无显著变化,总氮含量有所下降,水体微囊藻毒素MC—LR含量随着蓝藻密度的下降而降低,并讨论了尼罗与奥利亚罗非鱼摄食抑制蓝藻的摄食抑制及其对水质的影响。     

军曹鱼幼鱼日粮锌最适添加量的研究

在以卵白蛋白为蛋白源的基础饲料（Zn含量为5．65mg／kg）中添加10、20、30、40、50mg／kg以ZnSO4为Zn源的Zn,使饲料中总Zn含量为15．97、25．66、33．90、45．85、55．88mg／kg。投喂军曹鱼幼鱼8周。试验结果表明,基础饲料组鱼出现生长不良、厌食、皮肤糜烂和白内障等症状,其成活率、增重率、血清碱性磷酸酶活性（AKP）显著低于添加Zn组（P〈0．05）,骨骼、肌肉、血清和肝脏Zn含量也表现出相同趋势。10mg／kg和20mg／kgZn添加量组鱼仍出现缺Zn症状,各项测定指标随Zn添加量的增加而增大。当饲料中Zn添加量达到30mg／kg时,各项指标趋向稳定,与添加量40mg／kg和50mg／kg组无显著差异。以增重率和骨骼Zn含量为主要评价指标,通过回归分析表明,以ZnSO4为Zn源时,军曹鱼幼鱼日粮Zn的最适添加量为42．86mg／kg。     

Dietary Niacin Requirement of GIFT Tilapia,Oreochromis niloticus,Reared in Freshwater

The aim of our experiment was to determine the dietary niacin requirement of genetically improved farmed tilapia (GIFT) tilapia, Oreochromis niloticus, reared in freshwater. Six semi‐purified diets were formulated to contain graded levels of niacin (6.4 [basal diet], 16.8, 36.8, 68.5, 143.8, and 297.8 mg/kg). Each diet was fed to triplicate groups of 30 fish (initial average weight 87.2 ± 3.3 g) for 12 wk in 5.6‐m³ aquaria (r = 1.5 m, h = 0.8 m). Results showed that the weight gain rate (WGR) of the fish increased linearly with dietary niacin levels increasing, but there were no further benefits above 36.8 mg/kg. The niacin concentrations in fish livers were positively correlated with dietary levels of niacin and plateaued when niacin in diet exceeded 84.6 mg/kg. With increasing dietary niacin level, serum high density lipoprotein cholesterol (HDLC) content significantly increased, while serum triacylglycerol (TG) content significantly decreased (P < 0.05). There were no significant differences in serum glucose (GLU) and total cholesterol (T‐CHO) contents in the separate fish groups (P > 0.05). Broken‐line regression analysis showed that GIFT tilapia (87–376 g) require a minimum of 20.4 mg/kg niacin in the diet for maximal growth, and 84.6 mg/kg for the highest liver niacin accumulation.     

Effects of Thermal and Thermo-Haline Shocks on Survival and Osmotic Concentration of the Tilapias Oreochromis mossambicus and Oreochromis aureus × Oreochromis niloticus Hybrids

Abstract.— The effects of thermal and thermo/haline shocks on the tilapias Oreochromis mossambicus and O. aureus × O. niloricus hybrids were investigated. Fingerlings were transferred abruptly from 25 C fresh water to fresh water or salt water (26 ppt) maintaining temperatures of 15, 20, 30 and 35 C. In fresh water, fish survival was not affected by temperature shock, but they suffered from a chill coma and developed fungal infection at 15 C. In salt water, thermo-haline shock did not affect the survival of O. mossambicus , while the survival rates of tilapia hybrids were 6.7, 100, 100, 70 and 59.7% at 15, 20, 25, 30 and 35 C, respectively. Plasma osmotic concentrations of O. mossambicus transferred to 15 and 35 C salt water were quickly and sharply increased, but gradually decreased to lower levels. Osmotic concentrations of tilapia hybrids were also increased, but never returned to their initial (lower) levels over one week. This study revealed that these fishes are more tolerant to high rather than low temperature shocks and O. mossambicus are more resistant to thermo-haline shocks rather than tilapia hybrids. It also indicated that thermo-haline shocks should be minimized during fish transportation and acclimation.     

奥利亚罗非鱼全人工繁殖试验

对奥利亚罗非鱼全人工繁殖技术和胚胎发育进行了初步的研究。结果表明,成熟亲鱼注射DOM和LRH-A2进行催产,能够成功地进行人工繁殖。水温26～28℃时,催产率为62.5%,效应时间为28～36h,孵化时间为78～90h。     

大规格优质奥尼罗非鱼养殖试验

在2.13 hm2的池塘中投放平均体质量370 g的奥尼罗非鱼鱼种34 000尾,经124 d养殖,奥尼罗非鱼平均1.12 kg/尾,最大为1.81 g/尾,平均体长29.3 cm,最大为35.5 cm。奥尼罗非鱼产量38 050 kg,总产值30.9万元,获利9.1万元,经济效益显著。选用良种是基础,投喂优质饲料是关键。     

罗非鱼养殖技术之三奥尼罗非鱼与淡水白鲳池塘混养技术

奥尼罗非鱼是雄性奥利亚罗非鱼和雌性尼罗罗非鱼杂交仔一代,具有适应性广、雄性率高、食性杂、饲料利用率高、抗病力强、群体生长快、产量高等优点,是一个优质高产的好品种,适合在各种水面进行养殖.淡水白鲳学名为短盖巨脂鲤,属脂鲤目、脂鲤科、巨脂鲤属,是热带和亚热带食用与观赏兼备的大型经济鱼类,具有体型大、生长快、食性广、病害少、耐低溶解氧、易起捕、好垂钓等优点,己成为池塘养殖的当家品种.     

Thiamin Requirement of Nile Tilapia,Oreochromis niloticus

Juvenile Nile tilapia, Oreochromis niloticus, were fed to apparent satiation twice daily with purified diets containing 0, 1.0, 2.0, 4.0, 8.0, and 16.0 mg/kg and 0, 2.0, 4.0, 8.0, 16.0, and 32.0 mg/kg of thiamin in separate 14‐ and 8‐wk trials (Experiments 1 and 2, respectively). Fish fed the diet devoid of thiamin developed neurological disorders, anorexia, reduced growth, and feed efficiency and increased mortality (Experiment 2 only) within 4–6 and 8–10 wk for Experiments 2 and 1, respectively. Low red blood cell count (RBC) and hematocrit (Ht) were observed in fish fed the thiamin‐deficient diet. Serum pyruvate was elevated in fish fed the thiamin unsupplemented diet. Serum lactate was not affected by dietary thiamin levels. Whole body protein was unaffected by dietary levels of thiamin. Body moisture and ash increased whereas body lipid decreased in fish fed the thiamin unsupplemented diets. None of these abnormalities were observed in fish fed the thiamin‐supplemented diets. Using the response curves determined by PROC NLMIXED to estimate dietary thiamin levels required for various response variables, a dietary thiamin level of 3.5 mg/kg diet was adequate for optimum growth, feed intake and efficiency, survival, prevention of neurological symptoms, and maintaining normal levels of RBC, Ht, serum pyruvate, and proximate body composition.     

罗非鱼养殖技术之一大水面网箱养殖奥尼罗非鱼技术

大水面是渔业生产重要的水资源,发展大水面渔业具有广阔的前景。为此,作者于2005年在24万亩的东江湖水面中开展了网箱养殖奥尼罗非鱼试验,获得成功并取得了很好的效果和效益。一、大水面养殖条件 1．地理位置东江湖位于郴州市所辖的资兴市境内,耒水上游,于 1986年关闸蓄水,集雨面积4719km2,正常水位24万亩,库容81亿方,为湖泊与山谷型兼容的大型水库。 2．地形地貌东江湖周围的资兴市境内以山地为主,东南高,西北低,土壤以红、黄土壤为主,丘陵、岗地、平地交错。其中,平     

Optimal Dietary Protein Concentration for Hybrid Tilapia Oreochromis niloticus × O. aureus Fed All-Plant Diets

There are several estimates of the optimal dietary crude protein concentration for juvenile tilapia fed high quality animal proteins or mixtures of animal and plant derived feedstuffs. In the present study, the optimal dietary crude protein concentration for hybrid tilapia Oreochromis niloticus × O. aureus reared in glass aquaria was determined using diets free of fish meal. Further, initial weight of fish was approximately 21 g, which is the beginning of the growout phase of many commercial operations. The diets contained primarily corn co-products and soybean meal as the sources of amino acids, and were formulated to provide 24, 26, 28, 30, 32 or 34% crude protein. The diets were fed to quadruplicate groups of tilapia for 10 wk. Increasing concentrations of dietary crude protein resulted in proportional improvements in weight gain and feed efficiency up to 30% dietary crude protein. Fish fed 24% dietary crude protein exhibited significantly reduced weight gain compared to fish fed 28–34% dietary crude protein. Protein efficiency ratio (PER) of tilapia was unaffected by dietary crude protein concentration. However, fish fed 28% crude protein exhibited numerically higher PER (2.58) than fish fed other levels of crude protein. Muscle crude protein levels were lower in fish fed diets containing 24–28% crude protein than in fish fed 30% and higher concentrations. Quadratic regression analyses of weight gain and feed efficiency data indicated the optimal dietary crude protein concentration to be 29.65% and 28.33%, respectively, while broken line analyses indicated 27.5 and 27.3%, respectively. Based on weight gain, feed efficiency, PER, and proximate composition data, the authors recommend 28% dietary crude protein as the minimum for hybrid tilapia fed all-plant diets and reared in tanks.     

奥利亚罗非鱼、尼罗罗非鱼MyoD1和MyoD2基因特征及差异

采用RT-PCR和RACE法,分离了奥利亚罗非鱼(Oreochromis aureus)、尼罗罗非鱼(O.niloticus)MyoD1和MyoD2基因全长cDNA。结果显示,2种罗非鱼MyoD1全长均为1090bp,包括5′非翻译区(UTR)137bp,3′UTR50bp,开放阅读框(ORF)903bp,编码300个氨基酸,其中第110～161个氨基酸为bHLH结构,第233～249个氨基酸为helixIII结构;MyoD2全长均为1478bp,包括5′UTR215bp,3′UTR471bp,ORF792bp,编码263个氨基酸,其中第91～142个氨基酸为bHLH结构,第212～228个氨基酸为helixIII结构。2种罗非鱼MyoD1与其他鱼类MyoD1的相似性为73%～92%;MyoD2与其他鱼类MyoD2的相似性为74%～79%。系统发育树显示,MyoD1和MyoD2分属两支,MyoD1所反映的不同鱼类间的亲缘关系符合传统分类。2种罗非鱼的MyoD1、MyoD2cDNA序列之间只存在个别碱基的差别,而氨基酸序列一致;奥利亚罗非鱼MyoD1的2个内含子均比尼罗罗非鱼的长。根据MyoD1内含子2的差异构建鉴别奥利亚罗非鱼和尼罗罗非鱼基因混杂的标记,对形态上典型的15尾奥利亚罗非鱼、18尾尼罗罗非鱼及15尾奥尼罗非鱼[Oreochromis aureus(♂)×Oreochromis niloticus(♀)]进行鉴定。结果其中1尾奥利亚罗非鱼中在MyoD1位点混杂了尼罗罗非鱼的基因,尼罗罗非鱼和奥尼罗非鱼则与预期的一致。该研究为选择基因纯合的奥利亚罗非鱼和尼罗罗非鱼提供了新的分子手段。     

Dietary Valine Requirement of Fingerling Catla catla

A 12-week feeding trial was conducted to determine the dietary valine requirement of fingerling Catla catla (3.50 ± 0.15 cm, 0.63 ± 0.04 g). Seven casein gelatin-based diets (33% crude protein; 3.34 kcal/g digestible energy) containing graded levels of valine (0.51%, 0.69%, 0.91%, 1.12%, 1.31%, 1.49%, 1.71% dry diet) were fed to triplicate groups of fish to apparent satiation at 08:00, 12:30, and 17:30 h. Absolute weight gain (AWG), feed conversion ratio (FCR), specific growth rate (SGR%), protein efficiency ratio (PER), protein productive value (PPV), valine retention efficiency (VRE), valine gain (VG), energy retention efficiency (ERE), and carcass protein improved significantly (P < 0.05) with the increasing concentrations of dietary valine from 0.51% to 1.12%. Quadratic regression analysis of AWG, PPV, DPD, VG, ERE, and carcass protein at 95% maximum (Y_95%max) response against varying levels of dietary valine yielded the requirement at 1.04%, 1.03%, 1.05%, 1.04%, 1.01%, and 0.98% of dry diet, respectively. It is recommended that inclusion of valine at 1.02% of dry diet, corresponding to 3.09% of dietary protein, is optimum in formulating valine-balanced feeds for fingerling C. catla.