一种赖氨酸芽孢杆菌对凡纳滨对虾生长和水质影响

为探讨一种赖氨酸芽孢杆菌对凡纳滨对虾生长、存活和养殖水质的影响。设1个试验组和1个对照组,每组3个平行,125尾对虾/桶,初始体质量(5.18±0.13) g、体长(9.40±0.18) cm、水温(26±2)℃、盐度30、试验时间10 d。试验组定期添加浓度为0.463×10⁹ CFU/mL的赖氨酸芽孢杆菌菌液,试验组和对照组NH⁺₄-N质量浓度变化范围分别为(0.05±0.01)～(5.51±0.09) mg/L、(0.05±0.01)～(6.07±0.22) mg/L。NO^-₂-N质量浓度变化范围分别为(0.07±0.01)～(0.13±0.01) mg/L、(0.07±0.01)～(0.19±0.01) mg/L。NO^-₃-N质量浓度变化范围分别为(0.07±0.01)～(0.81±0.07) mg/L、(0.07±0.01)～(1.26±0.07) mg/L。pH的变化范围分别为(7.10±0.01)～(7.74±0.01)...     

Ca2 浓度对凡纳滨对虾稚虾生长的影响

研究了Ca2 浓度对凡纳滨对虾稚虾生长的影响。实验保持盐度15和其它离子的浓度基本恒定,共设计了5个Ca2 浓度梯度,分别为60(R1)、180(R2)、750(R3)、3750(R4)和7500 mg·L-1(R5)。经过35 d的养殖实验,结果表明:(1)不同Ca2 浓度的人工海水对凡纳滨对虾的存活率影响显著,R1组虾的存活率最低,为81.25%,显著低于R2、R3和R4的存活率;(2)5个Ca2 浓度下凡纳滨对虾生长速度不同,其特定生长率(SGRd)的大小顺序为:R3>R2>R1>R4>R5,其中R3的特定生长率(SGRd)显著高于其它4组,而R5的特定生长率(SGRd)显著低于其它4组;(3)各个处理组虾的摄食率(FId)与特定生长率(SGRd)的趋势相反,表现为R5 >R4>R2>R1>R3,其中R5的摄食率显著高于R2、R1和R3的摄食率;(4)不同Ca2 浓度对对虾的食物转化率(FCE)影响显著。Ca2 浓度最大的R5组虾的食物转化率显著低于其它各组,而R3组虾的食物转化率显著高于其它各组;(5)各组虾的生长能、呼吸能和排泄能占摄食能的比例受不同Ca2 浓度的影响显著。本实验的结果表明,Ca2 浓度是通过影响凡纳滨对虾摄食和代谢率实现对其生长能积累影响的。在对虾养殖生产中, 适当提高养殖水体的Ca2 浓度,可提高养殖效果。     

盐度和营养对凡纳滨对虾蜕壳和生长的影响

采用实验生态学方法以初始体质量为(2.01±0.02) g的凡纳滨对虾为研究对象,投喂不同蛋白水平饲料,实验周期30 d,研究了盐度和饲料蛋白水平对凡纳滨对虾蜕壳和生长的影响。实验采用5×3析因设计,盐度梯度设置为6、12、18、24、30五个水平,饲料蛋白水平梯度设置为30%、36%、42%三个水平。结果表明:(1) 对虾蜕壳相对增重率呈现出随盐度上升而降低的变化趋势,以盐度为6时蜕壳相对增重率为最高。盐度和饲料蛋白水平及其交互作用对实验对虾蜕壳相对增重率影响差异显著(P＜0.05);对虾的特定生长率随盐度升高而上升,盐度和饲料蛋白水平对特定生长率影响差异显著(P＜0.05),其交互作用对特定生长率影响差异不显著。(2) 实验对虾的蜕壳频率,在低盐度水平下随盐度的增加而显著增加(P＜0.05),盐度18时蜕壳频率达到最高,之后随盐度的升高蜕壳频率下降,差异不显著。各盐度水平下,以中等蛋白质水平饲料组(36%)对虾蜕壳频率较高。方差分析表明,盐度和饲料蛋白水平对蜕壳频率影响差异显著(P＜0.05),其交互作用对蜕壳频率影响差异不显著。(3) 对虾蜕壳间期随盐度升高呈先延长后缩短的变化趋势。盐度对对虾蜕壳间期影响差异显著(P＜0.05),饲料蛋白水平单因子以及它和盐度的交互作用对对虾蜕壳间期影响不显著。     

微生态制剂对凡纳滨对虾促生长作用试验

将微生态制剂菌株J-10添加到饲料中投喂凡纳滨对虾,结果表明,微生态制剂可在一定程度上促进对虾的生长。最适添加量为质量分数0.15%~0.2%,过量添加反而会使对虾生长减慢。     

饲料脂肪水平对凡纳滨对虾生长、肌肉和肝胰腺脂肪酸组成的影响

以脂肪水平为4.64%、6.56%、8.47%、10.39%和12.31%的5组试验饲料,饲喂凡纳滨对虾[初始质量(9.84±0.14)g].水温为23.4～27.0℃,60 d.饲养结果显示,体质量增加及成活率以8.47%脂肪含量组最佳;雄虾肝胰腺中的C18:3n-3,雄虾肌肉脂质中C20:4 n-6、C20:5n-...     

益生菌对凡纳滨对虾免疫功能及肠道菌群的影响

以类芽孢杆菌和双歧杆菌为益生菌,添加到凡纳滨对虾(平均体质量3.45g)的饲料中,饲养28d(水温25~27℃,盐度25~26,pH 7.8~8.1,溶解氧6mg/L),采用南京建成试剂盒和变性梯度凝胶电泳技术,研究益生菌对凡纳滨对虾免疫功能及肠道菌群的影响。结果表明,益生菌能够显著提高对虾血清过氧化物酶(对照组43.22U/mL,试验组76.33U/mL)、超氧化物歧化酶(对照组60.61U/mL,试验组101.18U/mL)、一氧化氮合酶(对照组7.54U/mL,试验组12.44U/mL)、酸性磷酸酶(对照组0.0446U/mL,试验组0.0574U/mL)和碱性磷酸酶(对照组0.0183U/mL,试验组0.0236U/mL)的活性(P0.01),明显改善对虾肠道的菌群组成,从而提高对虾抵抗疾病的能力。     

芽孢杆菌对凡纳对虾生长和消化酶活性的影响

选用豆粕、鱼粉、植物油、淀粉等原料配制基础料为对照组,在基础饲料中分别添加0.5％、1.0％、3.0％、5.0％芽孢杆菌(Bacillus subtilis)制剂为实验组。实验结果显示,凡纳对虾(Pennaus-vannamei)生长的2个阶段,实验组γSGR均大于对照组;生长第1阶段,组1与组2差异显著(P<0.05),与其余3组差异不显著(P>0.05),但各实验组之间差异均不明显(P>0.05);生长第2阶段,组1与组2之间γSGR差异极显著(P<0.01),与其余3组差异不明显(P>0.05),但各实验组间:组2与组4γSGR差异显著(P<0.05),而与组5γSGR差异极显著(P<0.01);对虾生长2个阶段的成活率实验组均略高于对照组,第1阶段的成活率明显高于第2阶段;芽孢杆菌对凡纳对虾2个生长阶段消化酶活性的影响表现出一定的相似性:实验组蛋白酶活性较淀粉酶、脂肪酶和纤维素酶高,且明显高于对照组,但各实验组间变化不明显。表明芽孢杆菌可以提高凡纳对虾消化酶活性和成活率,利于养分的消化吸收,促进生长。     

小球藻生长因子对凡纳滨对虾生长及营养成分的影响

为探明饲料添加小球藻生长因子对对虾生长性能、基础体成分和营养成分的影响,以凡纳滨对虾幼虾为试验对象,在基础饲料中分别添加0%、0.5%、1.0%、5.0%、10.0%、15.0%的小球藻生长因子,进行45 d的养殖试验,测定其生长性能、基础体成分和营养成分。试验结果显示,饲料添加小球藻生长因子能够提高凡纳滨对虾的存活率、质量增加率和特定生长率,降低饲料系数。饲料中添加小球藻生长因子能够降低凡纳滨对虾水分、粗脂肪和灰分含量,提高虾体粗蛋白含量,其中1%组凡纳滨对虾水分、粗脂肪、灰分均最低,粗蛋白最高。饲料添加10.0%～15.0%的小球藻生长因子凡纳滨对虾脂肪酸总量、饱和脂肪酸、单不饱和脂肪酸和多不饱和脂肪酸含量显著升高。饲料添加小球藻生长因子能够提高凡纳滨对虾多不饱和脂肪酸占比,降低饱和脂肪酸和单不饱和脂肪酸占比,其中1.0%组凡纳滨对虾饱和脂肪酸占比最低。饲料添加不同比例小球藻生长因子(除10.0%组)能显著提高肌肉氨基酸总量和必需氨基酸含量(P<0.05)。试验结果表明,饲料添加一定比例的小球藻生长因子能够提高凡纳滨对虾存活率和生长性能,降低水分、脂肪、灰分比例,提高蛋白比例...     

中草药添加剂对凡纳滨对虾生长和抗病力影响的研究

在凡纳滨对虾饲料中分别添加0、0.5g/kg、1.0g/kg和1.5g/kg的自制中草药添加剂,制成4种实验性饲料,饲养平均体长为(4.75±0.51)cm、平均体重为(0.77±0.24)g的凡纳滨对虾60天,以研究不同添加量对其生长和免疫的影响。测定了凡纳滨对虾的日增重率、相对增长率、成活率、饲料系数和抗病力。结果表明,该中草药制剂可明显提高凡纳滨对虾的生长和抗病力。以促生长角度考虑,添加1.0g/kg是合适的,而从提高免疫力方面考虑,添加1.5g/kg较为合适。     

硒源对凡纳滨对虾生长、体组成和抗氧化能力的影响

水温(29.0±1.3)℃,将初始体质量(0.41±0.01)g的凡纳滨对虾随机分为4组,每组3个重复,饲养在室内循环水养殖系统中,投喂基础饲料(对照组)及在此饲料中分别添加硒含量相等(0.30mg/kg)的亚硒酸钠、酵母硒和蛋氨酸硒的4种饲料,养殖56d,比较了不同硒源对凡纳滨对虾生长、体组成和抗氧化能力的影响。试验结果表明,蛋氨酸硒组对虾的生长性能显著高于对照组和亚硒酸钠组(P0.05)。外源硒可显著影响对虾体蛋白和脂肪含量(P0.05),蛋氨酸硒组对虾机体营养成分显著优于其他组(P0.05)。添加外源硒组对虾的血清总抗氧化能力和谷胱甘肽过氧化物酶活性显著高于对照组(P0.05)。蛋氨酸硒组对虾血清丙二醛含量显著低于其他组(P0.05)。由此得出,饲料添加0.3mg/kg的硒能在一定程度上提高凡纳滨对虾的生长和抗氧化能力,蛋氨酸硒优于酵母硒和亚硒酸钠。     

Effects of dietary lipid sources on growth and fatty acid composition of juvenile shrimp, Litopenaeus vannamei

This experiment was conducted to evaluate the effects of dietary lipid sources on the growth performance and fatty acid (FA) composition of juvenile shrimp, Litopenaeus vannamei. Six isoenergetic and isonitrogenous semi‐purified diets containing casein, solvent‐extracted soybean meal and gelatin as protein sources, were supplemented with 60 g kg⁻¹ of lipid sources. The lipid sources included: pollack fish oil (PO), pork lard (PL), soy oil (SO), peanut oil (PN), rapeseed oil (RO) and a mixture of pollack fish oil and soy oil (POSO 1 : 1 w/w). Each diet was fed to juvenile shrimp (0.10 g average weight) four times daily in triplicate tanks to apparent satiation (feeding ratio was about 8%) for 8 weeks. At the end of the experiment, weight gain, specific growth rate and protein efficiency ratio were significantly higher for shrimp fed the diet containing PO and the POSO mixture oil than the other lipid sources. The nutritional values of SO, RO, PN and PL were similar. Shrimp fed on PO, mixture oil of POSO and SO had better survival rates than the other lipid sources, and shrimp fed the PL had the lowest survival rate. There were significant differences in lipid contents of whole body and hepatopancreas amongst the dietary treatments; however, lipid contents of tail muscle were not significantly affected by the dietary lipid sources. Shrimps fed POSO diet had higher protein content in whole body than those fed the other lipid sources, and shrimp fed PO diet had highest crude protein content of the tail muscle. A high correlation was found between dietary FA composition and FA composition of whole shrimp. FA composition of the whole body was generally affected by dietary lipid sources, especially dietary unsaturated FA.     

Growth and body composition of juvenile white shrimp,Litopenaeus vannamei,fed different ratios of dietary protein to energy

A 10‐week feeding experiment was conducted to evaluate the effect of different protein to energy ratios on growth and body composition of juvenile Litopenaeus vannamei (initial average weight of 0.09 ± 0.002 g, mean ± SE). Twelve practical test diets were formulated to contain four protein levels (300, 340, 380 and 420 g kg^?1) and three lipid levels (50, 75 and 100 g kg^?1). Each diet was randomly fed to triplicate groups of 30 shrimps per tank (260 L). The water temperature was 28.5 ± 2 °C and the salinity was 28 ± 1 g L^?1 during the experimental period. The results showed that the growth was significantly (P < 0.05) affected by dietary treatments. Shrimps fed the diets containing 300 g kg^?1 protein showed the poorest growth. However, shrimp fed the 75 g kg^?1 lipid diets had only slightly higher growth than that fed 50 g kg^?1 lipid diets at the same dietary protein level, and even a little decline in growth with the further increase of dietary lipid to 100 g kg^?1. Shrimp fed the diet with 420 g kg^?1protein and 75 g kg^?1 lipid had the highest specific growth rate. However, shrimp fed the diet with 340 g kg^?1 protein and 75 g kg^?1 lipid showed comparable growth, and had the highest protein efficiency ratio, energy retention and feed efficiency ratio among dietary treatments. Triglycerides and total cholesterol in the serum of shrimp increased with increasing dietary lipid level at the same dietary protein level. Body lipid and energy increased with increasing dietary lipid level irrespective of dietary protein. Results of the present study showed that the diet containing 340 g kg^?1 protein and 75 g kg^?1 lipid with digestible protein/digestible energy of 21.1 mg kJ^?1 is optimum for L. vannamei, and the increase of dietary lipid level has not efficient protein‐sparing effect.     

饲料中添加核苷酸对凡纳滨对虾幼虾生长、组织生化组成及非特异性免疫功能的影响

选用960尾初始体重为(0.43?0.01) g 的凡纳滨对虾,随机分为8组,分别投喂基础饲料和7种添加核苷酸混合物(mix-NT)的试验饲料,5种核苷酸(5′-腺苷酸∶5′-胞苷酸∶5′-尿苷酸二钠∶5′-肌苷酸二钠∶5′-鸟苷酸二钠)按照质量比为1∶1∶1∶1∶1(W/W)混合,添加量分别为0.1、0.2、0.4、0.6、0.8、1.0和1.2 g/kg 饲料,试验周期为5周。结果显示,当mixNT添加量为0.4 g/kg饲料时,凡纳滨对虾的增重率(WGR)、特定生长率(SGR)和摄食量(FI)显著高于对照组(P<0.05),饲料系数(FCR)比对照组降低5.5%(P>0.05)。0.6和1.0 g/kg mix-NT添加组的蛋白质沉积率(PDR)显著高于对照组(P<0.05)。试验组对虾存活率(SR)和肝胰指数(HSI)均不同程度的高于对照组,但差异不显著(P>0.05)。饲料中添加mix-NT对全虾粗脂肪、灰分含量的影响显著(P<0.05),各mix-NT添加组的全虾干物质和粗蛋白含量均高于对照组,但差异未达到显著水平(P>0.05)。肝胰腺RNA含量和总蛋白(TP)含量均随饲料中mix-NT添加量的增加而升高,其中0.2~1.0 g/kg组的肝胰腺RNA含量显著高于对照组(P<0.05),TP含量差异未达到显著水平(P>0.05);各mixNT添加组的肠道TP含量均显著高于对照组(P<0.05),0.4和0.6 g/kg组的肠道RNA量极显著高于对照组(P<0.01)。外源mix-NT显著降低血清尿酸(UA)含量(P<0.05),但对TP、谷丙转氨酶(GPT)、高密度脂蛋白(HDL)含量无显著影响(P>0.05)。当mix-NT添加量为1.2 g/kg 饲料时,血清中谷草转氨酶(GOt)活性显著性升高(P<0.05)。鳃和肌肉酚氧化酶(PO)活性均在0.4 g/kg组达到最大,其中0.1～0.6 g/kg 组的鳃PO活性显著高于对照组(P<0.05),而各组肌肉PO活性无显著差异(P>0.05)。凡纳滨对虾肝胰腺和血清中溶菌酶(LZM)活性随饲料中mix-NT添加量的增加而显著升高(P<0.05)。结果表明,饲料中添加一定量的5种核苷酸混合物能显著提高凡纳滨对虾幼虾的增重率、特定生长率、摄食量、蛋白质沉积率、全虾粗脂肪和灰分含量,一定程度提高全虾粗蛋白和肝胰腺总蛋白含量,显著增加肝胰腺RNA、肠道总蛋白和RNA含量,提高对虾的非特异性免疫功能。     

低聚木糖对凡纳滨对虾生长、体组成和非特异免疫的影响

采用单因子试验设计在凡纳滨对虾(Litopenaeus vannamei)基础日粮中添加不同浓度的低聚木糖,分别为0(对照组)、0.01%、0.03%、0.05%,共4个处理,每个处理3个重复,饲养56 d,研究了低聚木糖对凡纳滨对虾生长性能、体组成和非特异免疫的影响。结果显示:低聚木糖对对虾末重、增重率和特定生长率均无显著影响(P>0.05),但试验组对虾末重、增重率和特定生长率均高于对照组,试验组饵料系数均较对照组下降,其中0.03%组饵料系数显著低于对照组(P<0.05),试验组饲料效率较对照组均有提高,其中0.03%组获得显著提高(P<0.05);血清免疫指标过氧化物酶(POD)、超氧化物歧化酶(SOD)、溶菌酶(LSZ)和酚氧化酶(PO)活力试验组均较对照组有所增加,分别提高了1.27%~5.16%(P>0.05)、0.17%~8.93%(P>0.05)、9.24%~12.61%(P>0.05)和4.17%~66.67%(P<0.05),血清蛋白含量增加了9.72%~39.64%(P<0.05);试验组体蛋白含量较对照组升高,其中0.01%组虾体蛋白质含量最高,且显著高于空白组(P<0.05)。在凡纳滨对虾料中添加低聚木糖有促进生长、降低饵料系数和提高饲料效率的趋势,并提高对虾非特异免疫力的趋势,对对虾体组成除蛋白质外没有显著影响。     

饲料中益生菌对凡纳滨对虾生长、肠道菌群及部分免疫指标的影响

以初体质量为(0.11±0.00)g的凡纳滨对虾(Litopenaeus vannamei)为研究对象,在室外水泥池进行10周饲喂实验,研究饲料中添加单一益生菌和复合益生菌对凡纳滨对虾生长、消化酶、肠道和粪便菌群及部分免疫指标的影响.以基础饲料为对照组,在基础饲料中分别添加地衣芽孢杆菌(Bacillus licheniformis)、枯草芽孢杆菌(Bacillus subtilis)、虾乐333(复合益生菌)、地衣芽孢杆菌+枯草芽孢杆菌(1:1)、虾乐333+地衣芽孢杆菌+枯草芽孢杆菌(1:1:1)各1 g/kg,配制5种实验饲料.实验结果显示,复合益生菌饲喂组对虾的特定生长率显著高于对照组(P<0.05),而单一益生菌饲喂组与对照组差异不显著(P<0.05).饲料中添加益生菌能使凡纳滨对虾肠道蛋白酶和淀粉酶活力升高,其中复合益生菌饲喂组淀粉酶活力显著高于对照组(P<0.05).与对照组比,饲料中添加益生菌显著降低了肠道及粪便弧菌数(P<0.05),不同程度提高了凡纳滨对虾血清蛋白浓度、酚氧化酶活力、溶菌酶活力和总抗氧化力,其中添加复合益生菌能使血清蛋白浓度及溶菌酶活力较对照组显著提高(P<0.05).上述结果表明,与饲喂单一益生菌相比,复合益生菌对凡纳滨对虾的生长、免疫力具有更好的促进作用.     

几株肠道益生菌对凡纳滨对虾非特异免疫力和抗病力的影响

以基础饲料为对照组,在基础饲料中分别添加坚强芽孢杆菌活菌(Bacillus firmus)、坚强芽孢杆菌活菌(1.0×108 CFU/g)+美人鱼发光杆菌(Photobacterium damsela)灭活菌(1％)、坚强芽孢杆菌活菌(1.0×108 CFU/g)+溶藻弧菌(Vibrio alginolyticus)灭活菌(1％)配制3种免疫饲料.每组3个重复,对个体质量为(3.2±0.26)g的凡纳滨对虾(Litopenaeus vannamei)进行了为期30d的养殖实验.每5d取样,以血清中的酸性磷酸酶(ACP)、碱性磷酸酶(AKP)、一氧化氮合酶(NOS)、超氧化物歧化酶(SOD)和溶菌酶(UL)活性为免疫指标,探讨了肠道益生菌及其灭活菌体作为免疫制剂对凡纳滨对虾非特异性免疫水平的影响;在投喂免疫饲料后的第16天,按0.9 g/10尾剂量,直接投喂感染白斑综合征病毒(wssV)对虾病料,计算各实验组每天的累计死亡率,分析肠道益生菌及其灭活菌体作为免疫制剂对凡纳滨对虾病毒感染能力的影响.结果显示:添加益生菌的实验组对虾血清中SOD、ACP、AKP和NOS活性明显高于对照组(P＜0.05),特别是显著提高了对虾抗WSSV感染的能力.其中坚强芽孢杆菌活菌(1.0× 108 CFU/g)和美人鱼发光杆菌灭活菌(1％)实验组的抗病毒感染能力最强,感染WSSV 14 d后累计死亡率为10.71％;而对照组为64.28％.结论认为,饲料中添加肠道益生菌及其灭活菌体能提高凡纳滨对虾非特异性免疫水平和抵抗疾病的能力,有望作为新型对虾免疫增强剂应用于对虾养殖业.     

Influence of dietary phospholipids level on growth performance,body composition and lipid class of early postlarval Litopenaeus vannamei

One experiment was conducted to determine the nutritive value of phospholipids on growth performance of early postlarval shrimp, Litopenaeus vannamei. Five isoenergic and isonitrogenous diets with five supplemented levels of phospholipids (P1, P2, P3, P4 and P5 with 0, 10, 20, 40 and 80 g kg^?1 diet, respectively) were fed to triplicate groups of L. vannamei (mean initial wet weight 0.8 mg) for 27 days. After the 27‐day feeding trial, the lowest weight gain (WG, %) and specific growth rate (SGR, % day^?1) was found in P1 treatment, the highest WG and SGR was found in P3, P4 and P5 treatments, P2 treatment provided intermediate result and showed significant difference compared to P1, P3, P4 and P5 treatments. Shrimp fed the P1 diet had significantly lower survival than shrimp fed other diets, while no significant difference was found in survival among P2, P3, P4 and P5 treatments. Broken‐line analysis on WG indicated that the optimum dietary phospholipids for early postlarval shrimp, L. vannamei, is 45.96 g kg^?1 diet.     

Effects of dietary xylooligosaccharides on growth performance,immunity and Vibrio alginolyticus resistance of juvenile Litopenaeus vannamei

A 60‐day feeding trial was conducted to assess the effects of xylooligosaccharides on growth performance, immunity and Vibriosis alginolyticus resistance of juvenile Litopenaeus vannamei. Five diets were formulated to contain 0 (T0), 1 (T1), 2 (T2), 4 (T4) and 6 (T6) g/kg of xylooligosaccharides, triplicate groups of 40 shrimps with initial weight of 0.10 ± 0.01 g were fed to apparent satiation four times daily. At the end of the feeding trail, ten shrimps from each tank were challenged with V. alginolyticus. Results showed that shrimps fed xylooligosaccharides containing diets had higher (p < 0.05) feed efficiency, survival rate and intestinal villi length and area than those of T0. There was no significant difference in final body weight, weight gain rate and chemical compositions of whole shrimp among treatments. Shrimps fed T4 and T6 diets had higher (p < 0.05) phenoloxidase and lysozyme activities than those in T0. Concentration of albumin, phenoloxidase activity and survival rate of shrimps decreased (p < 0.05) after 72 hr of challenge, with SR being greater (p < 0.05) in T2, T4 and T6 than that of in T0. Results demonstrate that supplementing 4–6 g/kg of xylooligosaccharides in diets increased feed efficiency, survival rate, intestinal villi length and area, and improved the resistance of juvenile L. vannamei against V. alginolyticus. This study suggests that xylooligosaccharides could be a potential feed additive in practical diet of juvenile L. vannamei.     

Effect of dietary phosphorus sources and varying levels of supplemental phosphorus on survival,growth and body composition of postlarval shrimp (Litopenaeus vannamei)

Two experiments were conducted for 30 days each to investigate the effective phosphorus source and supplemental phosphorus levels for postlarval Litopenaeus vannamei. The first experiment was performed in postlarval shrimp (mean initial wet weight 2 mg) fed four isoenergic and isonitrogenous diets containing three supplemented inorganic phosphorus sources [D1: no supplemental phosphorus, D2: NaH₂PO₄·2H₂O, D3: KH₂PO₄·2H₂O, D4: Ca(H₂PO₄)₂·2H₂O]. The quantities of the three supplemental NaH₂PO₄·2H₂O, KH₂PO₄·2H₂O and Ca(H₂PO₄)₂·2H₂O were 11.6, 12.8 and 10 g kg^?1 of the diet, respectively in order to make the three diets have the same total phosphorus. Growth performance (final mean body weight, FBW; weight gain, WG; specific growth ratio, SGR) of shrimp in D3 treatment was the highest and had significant difference with the D1 treatment. The survival of shrimp in D3 treatment was the highest and had significant difference with the other treatments. The mineral concentration and body composition of shrimp were not significantly different among treatments. We could conclude that KH₂PO₄·2H₂O was the optimal phosphorus source for postlarval L. vannamei from the growth performance and survival. The second experiment was performed in postlarval shrimp (mean initial wet weight 0.88 mg) fed four isoenergic and isonitrogenous diets containing four supplemental KH₂PO₄·2H₂O levels (d1, d2, d3 and d4 with 0, 5, 10 and 20 g kg^?1, respectively). Shrimp in d2 treatment showed the highest growth performance and survival and also showed significant difference with other diet treatments. The whole body content of zinc (Zn) increased with the increase of dietary KH₂PO₄·2H₂O and significant differences were observed when dietary KH₂PO₄·2H₂O reached 5 g kg^?1, excess KH₂PO₄·2H₂O supplementation (10 and 20 g kg^?1) had a negative effect on Zn content, the Zn content significantly decreased when KH₂PO₄·2H₂O was 20 g kg^?1. We can conclude that the amount of total phosphorus in the diet should be maintained between 20.9 and 22.0 g kg^?1, the amount of supplemental KH₂PO₄·2H₂O in the diet is less than 10 g kg^?1.     

Effects of dietary chitosan on growth,survival and stress tolerance of postlarval shrimp,Litopenaeus vannamei

The effect of chitosan, a polymer of glucosamine obtained by the deacetylation of chitin, on growth, survival and stress tolerance was studied in postlarval Litopenaeus vannamei. An experiment was performed with postlarval shrimp (mean initial wet weight 1.2 mg) fed five isoenergic and isonitrogenous diets containing five supplemented levels of chitosan (0, 0.5, 1, 2 and 4 g kg^?1 diet, respectively). The five compound diets (C0, C0.5, C1, C2 and C4) sustained shrimp growth throughout the experiment. Growth performance (final body weights; weight gain; SGR: specific growth rate) in shrimp fed diet C2 was significantly higher than that in shrimp fed diets C0, C0.5 and C1 (P < 0.05), diet C4 treatment provided intermediate growth result. The survival in shrimp fed diet C1 was significantly higher than that in shrimp fed C0 diet (P < 0.05), other diets treatments gave the intermediate survival results. No significant differences were found in growth and survival between diet C2 and C4 treatments. After 9 days of a stress tolerance test, survival in shrimp fed diets C1, C2 and C4 was significantly higher than that in shrimp fed diets C0 and C0.5. We concluded from this experiment that the incorporation of a moderate dietary chitosan was beneficial to the development of postlarval L. vannamei. Considering the effect of chitosan on both growth and survival of postlarval L. vannamei, second‐degree polynomial regression of SGR and survival indicated optimum supplement of dietary chitosan at 2.67 and 2.13 g kg^?1, respectively, so the level of chitosan supplemented in the diet should be between 2.13 and 2.67 g kg^?1.