Juvenile Litopenaeus Vannamei Research Articles

Acute toxicity of nitrate in Litopenaeus vannamei juveniles at low salinity levels

ABSTRACT: Different technologies have been developed to improve the performance of Litopenaeus vannamei in low salinity, mainly in super-intensive systems like recirculation and BFT (Biofloc Technology System) systems. However, there is an accumulation of toxic nitrogenous compounds to the shrimps such as nitrate, that at high concentrations and depending on the salinity of the culture water can be lethal. Acute toxicity tests allow to analyze the relationship between the compound and other abiotic or biotic variables. The aim of this research was to determine the acute toxicity and safety level of nitrate (N-NO3 -) for juveniles of L. vannamei at salinities of 5 and 10g.L-1. For salinity of 5g.L-1, a control and 5 treatments were tested, with nitrate concentrations of 100, 500, 1500, 2500 and 3500mg.L-1.For salinity of 10mg.L-1, a 4500mg.L-1nitrate concentration was added. Juveniles were exposed to concentrations during 24, 48, 72, 96 hours in static system. The Mean Lethal Concentration (LCC50) was calculated and the recommended safety level for L. vannamei cultivation is 60.05 and 127.61mg.L-1 of nitrate for salinities 5 and 10g.L-1, respectively.

Increasing feed allowance in low-fish meal diets allows for a reduction in dietary methionine for juvenile Litopenaeus vannamei raised in green-water tanks

ABSTRACT A 10-week study was conducted to evaluate the effect of feed allowance and graded levels of dietary methionine (Met) on growth performance of Litopenaeus vannamei. Juvenile shrimp of 1.83±0.14 g were stocked in 42 outdoor green-water tanks of 1 m3 under 120 shrimp m−2. Animals were fed under two feed allowances, regular and 30% in excess. Five diets with 30 g kg−1 fishmeal were designed to contain 318±2 g kg−1 crude protein and a minimum amount of protein-bound Met. [...]

White spot syndrome virus (WSSV) infection and immunity responses in white shrimp (Litopenaeus vannamei ) exposed to sublethal levels of metals

To determine if exposure to a sublethal mixture of metals (Cd, Cu, Fe, Mn, Pb and Zn) increases susceptibility to White spot syndrome virus (WSSV) infection, Litopenaeus vannamei juveniles were fed WSSV-infected shrimp tissues after 21 days of exposure to the metal mixture (WS-MM treatment). Other treatments consisted of shrimp not exposed to metals and fed infected tissues (WS), and shrimp fed healthy tissues and exposed (MM) or not exposed to metals (C). The presence of viral DNA and inclusion bodies was detected at 32 hr postinfection (hpi) in the stomach epithelium of shrimp from the WS treatment, and eight hours later in shrimp from the WS-MM treatment, possibly because of an initial negative effect of metals in viral replication. At 40 hpi, the severity of infection represented by the histopathological index increased in both WS and WS-MM treatments, and values were higher in WS-MM than in WS shrimp at the end of the experiment. From 56 hpi to the end of experiment, total hemocyte counts were lower in both WS-MM and WS treatments, and concentrations were particularly low in WS-MM shrimp. Conversely, phenoloxidase activity was higher in the WS-MM treatment from 32 to 56 hpi, suggesting a possible role of the prophenoloxidase (proPO) system in the antiviral defense against WSSV. The presence of heavy metals at sublethal concentrations may increase shrimp susceptibility to WSSV; this is supported by a decrease in circulating hemocytes, an increase in the humoral response, and the development of a higher number of WSSV inclusion bodies.

EFEITO DA ALCALINIDADE NO CONSUMO ALIMENTAR DE JUVENIS DE CAMARÃO BRANCO DO PACÍFICO CULTIVADOS EM SISTEMA DE ÁGUA CLARA E BIOFLOCOS

Esse estudo objetivou avaliar o efeito da alcalinidade no consumo alimentar e demais parí­¢metros de desempenho de juvenis de Litopenaeus vannamei cultivados em água contendo bioflocos e água clara. Para tanto, durante 3 dias, camarões de 4,06 ± 0,34 g foram mantidos em recipientes de 3 L, sob as concentrações Controle, 50, 100 e 200 mg L-1 de alcalinidade, com 5 repetições cada, em bioflocos e água clara. O consumo alimentar foi verificado uma vez ao dia e os demais parí­¢metros de desempenho foram avaliados ao final do experimento. Nesse estudo, verifica-se que o consumo alimentar dos camarões não é afetado entre os ní­­veis de alcalinidade e nos sistemas de água clara e bioflocos. Já o ganho em peso e a taxa de crescimento especí­­fico são afetados positivamente nas maiores concentrações de alcalinidade, no sistema de bioflocos, onde demonstram os melhores resultados. E a sobrevivência, assim como o consumo alimentar, não é afetada entre os ní­­veis de alcalinidade e nos sistemas de água clara e bioflocos. Contudo, a possibilidade de exposição í­Â concentrações de alcalinidade inapropriadas, durante longos perí­­odos de tempo, pode afetar negativamente os animais, assim, ressaltando a importí­¢ncia da manutenção da alcalinidade em ní­­veis adequados í­Â espécie cultivada.

Multiple feedings enhance the growth performance and feed efficiency of juvenile Litopenaeus vannamei when fed a low-fish meal amino acid-supplemented diet

In the coming years, supplementation of crystalline amino acids (CAAs) will become a standard practice driven by the trend towards low-fish meal diets. We have evaluated the effect of feeding juvenile L. vannamei several times a day versus two (2×) and four (4×) times using a low-fish meal diet supplemented with CAAs. A total of 1632 shrimp of 1.06 ± 0.16 g were stocked in 16 outdoor tanks of 1 m3 under 100 shrimp/m2. Shrimp were either fed manually, 2× or 4× daily, using one feeding tray per tank, or fed with an automatic feeder to deliver multiple (10) meals during the day or during the day and night (D&N) at programmed times. A diet containing 3% fish meal was prepared to contain supplemental levels of CAAs. After 11 weeks of rearing, survival, growth performance, and feed efficiency of shrimp were significantly affected by feeding frequency and time of feeding. Feeding 2× and 4× daily resulted in a lower survival compared to multiple times during the day or D&N. Shrimp body weight was enhanced with an increase in feeding frequency, from 8.74, 10.95, 11.33, and 11.33 g under 2×, 4×, and multiple feedings during the day or during D&N, respectively. FCR was also significantly affected, reducing from a high of 2.46 under 2× to 1.59 under multiple feedings D&N. Our findings indicate that it is more advantageous to feed juvenile L. vannamei multiple times a day when a low-fish meal amino acid-supplemented diet is used.

Effect of low salinity on acute arsenic toxicity and bioconcentration in shrimp Litopenaeus vannamei juveniles

This study investigated acute arsenic toxicity and bioconcentration capacity in Litopenaeus vannamei because it has been frequently exposed to lower salinities than its isosmotic point (25 g L−1). Juveniles (9.9 ± 0.4 g) were exposed to low (5–10 g L−1) and isosmotic salinity (25 g L−1) levels; As values were 30.8, 20.2, 16.8 and 13.9 mg L−1 at 5 g L−1; 30.4, 19.1, 16.8 and 14.8 mg L−1 at 10 g L−1; 31.5, 19.0, 15.0 and 11.9 mg L−1 at 25 g L−1 at 24, 48, 72 and 96 h LC50, respectively. No significant differences were found among As LC50 values calculated for different salinity levels and same exposure times, concluding that low salinity did not affect shrimp sensitivity to As. Likewise, no significant differences were observed in As bioconcentration in shrimp exposed to the same waterborne As and distinct salinity, supporting the results of acute toxicity. Bioconcentration factors of As maintained a relatively stable tendency where all values (0.8 ± 0.2 to 1.7 ± 0.4) were statistically comparable to 1, indicating that As was accumulated in a similar proportion to waterborne As concentration at three salinity levels. This study proposed 135.3 ± 12.1 μg L−1 for salinities from 5 to 25 g L−1 as provisional safe As concentration. According to these results, the hypothesis that sustains an effect of low salinity on As acute toxicity and its bioconcentration capacity cannot be acceptable. Therefore, the information provided allows knowing the threshold levels of As in water to avoid ecological and economic losses.

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.

Acute Toxicity of Mercury and Nervous Tissue Damage in Postlarvae and Juveniles of Litopenaeus vannamei

Experiments were carried out to verify the existing information on the LC50 of waterborne Hg for L. vannamei postlarvae and determine that of juveniles. Additionally, the structure of different tissues of the organisms which survived the acute toxicity test was examined. The experiment with juveniles was performed after addition of 1.00, 0.75, 0.50, 0.25 and 0.10 mg/L of Hg (using HgCl2). For postlarvae, additions were 0.5, 0.4, 0.3, 0.2, 0.1 and 0.01 mg/L. Acute toxicity tests determined that, after 96 h of exposure to Hg, the respective LC50 values for juveniles and postlarvae of Litopenaeus vannamei were 0.50 and 0.25 mg/L. Although lower that the only value of LC50 known for L. vannamei postlarvae, these lethal concentrations are one order of magnitude higher than those known for larval and juvenile stages of other crustaceans, suggesting that L. vannamei has a high resistance to the toxic effects of waterborne Hg. The only histological damages in survivors to 96 h of exposure were observed in nervous tissues and consisted in the presence of necrotic cells. The degree of damage severity was related to the concentration of dissolved Hg, and the numbers of necrotic cells decreased progressively with increasing distance from the nerve ganglia. A safe level of mercury exposure for L. vannamei postlarvae would be 2.5 μg/L.

Utilization of IMTA-produced Ulva lactuca to supplement or partially replace pelleted diets in shrimp (Litopenaeus vannamei) reared in a clear water production system

Integrated multi-trophic aquaculture (IMTA) systems typically rely on macroalgae to maintain water quality for fed and extractive species. Macroalgae harvested from these systems can in turn be used as feed source for these species. This study evaluated the use of harvested Ulva lactuca from a land-based IMTA system as a partial replacement (25, 50%) or a supplement (25%) to a commercial shrimp diet for Litopenaeus vannamei juveniles. In addition to the impacts on shrimp production, the nutritional profile of the commercial diet and the macroalgae were compared. Thirty shrimp (1.17 ± 0.12 g) were stocked in 80-L tanks in a clear water system and fed either a commercial pellet (100F), a commercial diet supplemented with U. lactuca (100F:25U), or a partial replacement diet (75F:25U, 50F:50U) for 7 weeks. Survival was similar in all treatment groups; however, all growth parameters were significantly lower in the 50F:50U group, although feed conversion ratio was also lowered. The harvested Ulva contained high levels of protein (32%) and a similar amino acid profile to that of the commercial diet, although lipid levels were low (1.9%), and docosahexaenoic acid (DHA) was lacking. Shrimp in the partial replacement treatment groups had significantly lower protein levels. These results indicate that up to 25% of a commercial diet may be replaced with fresh U. lactuca without impacting shrimp production, and therefore, a cost savings in feed may be seen in an IMTA system producing both shrimp and Ulva.

Effects of two commercial feeds for semi-intensive and hyper-intensive culture and four C/N ratios on water quality and performance of Litopenaeus vannamei juveniles at high density in biofloc-based, zero-exchange outdoor tanks

A two-factor experiment was conducted to evaluate the effects of two commercial shrimp feeds and four different C/N ratios on biofloc development, water quality, growth performance, feed utilization and input cost in an outdoor tank system stocked with Litopenaeus vannamei juveniles under high-density and zero-exchange conditions. The two feeds used in the study were: a less expensive feed (US$0.99 kg−1) formulated for semi-intensive production systems and a more expensive one (US$1.75 kg−1) designed for hyper-intensive systems. Organic carbon (molasses) was added daily to provide calculated carbon to nitrogen (C/N) ratios of 12:1, 15:1, and 18:1 based on the carbon-nitrogen content of the feed and the carbon content of the molasses throughout the experiment. No molasses was added in the control group which had a C/N ratio of 9:1. Each treatment had four randomly assigned replicate tanks, and each tank filled with 500 L of biofloc-rich water. Juvenile shrimp (2.21 ± 0.11 g) were stocked into tanks at 150 shrimp tank−1 (300 juveniles m−3) and cultured for six weeks. The results showed that both feed and C/N ratio had significant effects on biofloc development, water quality, shrimp performance, feed utilization and input cost. Initiating the culture with biofloc-rich water and then adding a small amount of organic carbon regularly could effectively sustain the continued development of mixotrophic bioflocs in zero-exchange high-density shrimp culture systems. The best water quality, shrimp performance, and FCR results were achieved with the C/N ratio of 12:1 for both feeds. Analysis of feed and variable costs suggest improved economic benefits when using the less expensive feed of SI-35 under the conditions of this study. Furthermore, input costs could be decreased using a C/N ratio of 12:1 due mainly to reduced molasses and NaHCO3 usage.

Effect of dietary Syzygium cumini leaf powder on growth and non-specific immunity of Litopenaeus vannamei (Boone 1931) and defense against virulent strain of Vibrio parahaemolyticus

The study was aimed to assess the growth and immunomodulatory potential of Syzygium cumini leaf powder against virulent strain of Vibrio parahaemolyticus on the juveniles of Litopenaeus vannamei. Two diets such as control diet (without immunostimulant) and immunostimulant diet (containing 1% S. cumini leaf powder) were prepared. The juveniles were distributed in four treatments namely; daily feeding of control diet (CD), daily feeding of immunostimulant diet (ID), alternate day feeding of control and immunostimulant diet (CD/ID) and two days control diet and one day immunostimulant diet (2CD/ID) feeding. After feeding trial, shrimps from each treatment group were challenged with 0.1 mL of virulent strain of V. parahaemolyticus suspension at a concentration of 107 CFU mL−1. The post-challenge sampling was performed after 5 days of injection. The haemolymph prophenol oxidase, superoxide dismutase, catalase and respiratory burst activity of different treatments were significantly different (P < 0.05) in both pre- and post-challenge conditions. The haemolymph total protein, globulin, lysozyme and phagocytic activities of L. vannamei fed with Syzygium cumini leaf powder improved than the control group in pre- as well as post-challenge phase. The survival rate of shrimps fed with immunostimulant diet was significantly (P < 0.05) higher as compared to control group. Therefore, Syzygium cumini leaf powder added diet protects the host effectively against virulent strains of V. parahaemolyticus through both continuous and alternate day feeding.

Minimum water exchange spares the requirement for dietary methionine for juvenile Litopenaeus vannamei reared under intensive outdoor conditions

We examined if minimum water exchange could spare dietary methionine (Met) required for maximum growth performance of juvenile Litopenaeus vannamei reared in an intensive outdoor system. Shrimp of 1.98 ± 0.13 g were stocked at 70 animals/m2 and reared for 72 days in 50 tanks of 1 m3 under flow-through (14.4% a day) and static (1.4%–2.9% a day) green-water conditions at 32.0 ± 3.7 g/L salinity. Five diets with a minimum inclusion of fishmeal supplemented with a dipeptide, dl-methionyl-dl-methionine, were formulated to contain increasing levels of Met, 4.8, 6.2, 7.2, 8.1 or 9.4 g/kg (on a dry matter basis). Each of the five diets were fed four times daily to five replicate groups. Dietary Met and water exchange significantly influenced shrimp survival, gained yield, apparent feed intake, food conversion ratio and final body weight (p < .05). Raising shrimp under limited water exchange, i.e., static versus flow-through spared the dependence on higher levels of dietary Met to maximize shrimp body weight, from 9.4 g/kg to 8.0 g/kg (14.0 and 12.6 g/kg Met+Cys respectively). In an intensive rearing system, a reduction in water exchange is desirable as it leads to a lower need for supplemental dietary Met.

Effects of Lactobacillus acidophilus supplementation on the growth, enzyme activities, and mRNA expression of disease-resistance related enzymes of juvenile Litopenaeus vannamei

PDF HTML阅读 XML下载 导出引用 引用提醒 添加嗜酸乳杆菌对凡纳滨对虾生长、酶活性及相关酶mRNA表达的影响 DOI: 作者: 作者单位: 1. 广东海洋大学 水产动物营养与饲料实验室, 广东 湛江 524088;2. 农业农村部南方水产与畜禽饲料重点实验室, 广东 湛江 524074 作者简介: 李军亮(1991-),男,硕士研究生,研究方向为水产动物营养与饲料.E-mail:junliangli132@163.com 通讯作者: 中图分类号: S968 基金项目: 广东省科技厅社会发展领域科技计划项目（2013B021100017）；农业部南方水产与畜禽饲料重点实验室项目. Effects of Lactobacillus acidophilus supplementation on the growth, enzyme activities, and mRNA expression of disease-resistance related enzymes of juvenile Litopenaeus vannamei Author: Affiliation: 1. Laboratory of Aquatic Animal Nutrition and Feed, Guangdong Ocean University, Zhanjiang 524088, China;2. Key Laboratory of Aquatic, Livestock and Poultry Feed Science and Technology in South China, Ministry of Agri-culture and Rural Affairs, Zhanjiang 524074, China Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:本实验旨在研究饲料中添加嗜酸乳杆菌（）幼虾生长、非特异性免疫酶活性、抗病力和相关酶mRNA表达的影响。选取840尾初始均重为（0.58±0.01）g的凡纳滨对虾幼虾为研究对象，分为7个处理，每个处理3个重复。投喂添加不同比例（0%，0.1%，0.2%，0.4%，0.6%，0.8%，1.0%）嗜酸乳杆菌的饲料，养殖期8周。结果显示：添加不同比例嗜酸乳杆菌对凡纳滨对虾的成活率无显著影响（<0.05），在0.4%组达到最大值；当添加0.2%时，饲料系数最低，其他各组显著低于对照组（<0.05），而蛋白质效率的变化规律则与饲料系数相反。血清酚氧化物酶（phenoloxidase，PO）、碱性磷酸酶（alkaline phosphatase，AKP）和酸性磷酸酶（acid phosphatase，ACP）活性随添加量的增加先升高后降低，分别为0.4%、0.1%和0.2%时，达到最大值。过氧化氢酶（catalase，CAT）、溶菌酶（lysozyme，LZM）和超氧化物歧化酶（superoxide dismutase，SOD）活性，实验组均显著高于对照组（<0.05）。哈维弧菌（<0.05）。以增重率（weight gain rate，WGR）为判断依据，根据折线模型得出，饲料中添加0.23%嗜酸乳杆菌可显著促进凡纳滨对虾生长，并提高非特异性免疫酶活性。 Abstract:An 8-week feeding trial was carried out to investigate the effects of supplementation on the growth performance, nonspecific immunity-related enzyme activities, and disease resistance-related enzyme mRNA expression in juvenile , with initial average weight of 0.58±0.01 g, was randomly assigned to 7 groups in triplicates, with 40 individuals per replicate. Seven isonitrogenous and isolipid diets were supplemented with 0%, 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, and 1.0% in a basal diet, respectively. Following results were observed:nonsignificant difference was found in survival among all the groups (>0.05). Weight gain rate (WGR) and specific growth rate (SGR) increased gradually as dietary supplementation increased up to 0.4%, and then showed decline (<0.05). The minimum feed conversion rate (FCR) was observed on feed supplementation with 0.2% , which was significantly lower than that in the other groups (<0.05), while protein efficiency rate (PER) showed the opposite trend. Serum phenoloxidase (PO), alkaline phosphatase (AKP), and acid phosphatase (ACP) activities increased gradually with increasing dietary levels, and then gradually declined. The maximum values of PO, AKP, and ACP were found in the 0.4%, 0.1%, and 0.2% supplementation groups, respectively (<0.05). Activities of serum catalase (CAT), lysozyme (LSZ), and superoxide dismutase (SOD) of all treatment groups were significantly higher than that of the control group (0%) (<0.05). Gene expression levels of CAT and LZM in all treatment groups were significantly up-regulated when compared with the control group (<0.05). At the end of the feeding trial, the shrimps were challenged by for 96 h. Post-challenge survival rate increased with increasing dietary <0.05). Based on the broken-line regression analysis of WGR, when feed was supplemented with 0.23% of Litopenaeus vannamei were found to significantly improve. 参考文献 相似文献 引证文献

Arthrospira platensis filtrada como alimento complementario de juveniles del camarón blanco: efectos sobre crecimiento y sistema inmune

De forma general, las microalgas son fuente de alimento indispensable durante las primeras fases de desarrollo de los camarones marinos. Algunas microalgas, como la Arthrospira platensis, son ricas en substancias antioxidantes y tienen la capacidad de retirar compuestos tóxicos del agua en los sistemas de producción acuí­­cola. De este modo, constituimos un experimento con dos tratamientos triplicados, donde se evaluó la aplicación de biomasa filtrada de microalga A. platensis como suplemento alimenticio para camarón blanco del Pací­­fico, Litopenaeus vannamei. Se utilizó un sistema de cultivo estático de seis unidades, con volumen útil de 250 litros de agua marina (30 ppt), donde se sembraron 300 camarones m-2 con peso inicial de 0,7 ± 0,2 g. Al final del experimento (42 dí­­as) se evaluaron parámetros inmunológicos y de desempeí­±o zootécnico. Los camarones alimentados con A. platensis como suplemento fueron signicativamente mayores que los camarones del tratamiento control y no presentaron diferencias en la supervivencia. Igualmente, se obtuvieron mejores resultados en los parámetros inmunológicos del tratamiento con inclusión de microalga. De esta forma, al suministrar la microalga como alimento suplementario al camarón L. vannamei, crecimiento y sistema inmunológico se vieron favorecidos.

Replacement of fishmeal for soy protein concentrate in diets for juvenile Litopenaeus vannamei in biofloc-based rearing system

ABSTRACT This study aimed to assess the final body weight, weekly weight gain, yield, apparent feed efficiency, protein efficiency ratio, and feed intake of the Pacific white shrimp (Litopenaeus vannamei) fed four diets containing different levels of soy protein concentrate (SPC) as a replacement for fishmeal, reared in a super-intensive biofloc system. Diets consisted of replacing 209 g kg-1 fishmeal at 0, 33, 66, and 100% SPC. Shrimp were raised in a biofloc system using twelve experimental units stocked with [...]

Estimation of genetic parameters and genotype-by-environment interactions related to acute ammonia stress in Pacific white shrimp (Litopenaeus vannamei) juveniles at two different salinity levels

Regarding the practical farming of Litopenaeus vannamei, the deterioration of water quality from intensive culture systems and environmental pollution is a common but troublesome problem in the cultivation of this species. The toxicities that result from deteriorating water quality, such as that from ammonia stress, have lethal effects on juvenile shrimp and can increase their susceptibility to pathogens. The toxicity of ammonia plays an important role in the frequently high mortality during the early stage on shrimp farms. However, little information is available regarding the genetic parameters of the ammonia tolerance of juveniles in the early stage, but this information is necessary to understand the potential for the genetic improvement of this trait. Considering the euryhalinity of L. vannamei and the fact that low salinity can increase the toxicity of ammonia stress, we estimated the heritability of ammonia tolerance in juveniles in 30‰ (normal) and 5‰ (low) salinity in this study using the survival time (ST) at individual level and the survival status at the half-lethal time (SS50) at the family level. In the normal and low salinity conditions and for the merged data, the heritability estimates of the ST (0.784±0.070, 0.575±0.068, and 0.517±0.058, respectively) and SS50 (0.402±0.061, 0.216±0.050, and 0.264±0.050, respectively) were all significantly greater than zero, which indicates that the ammonia-tolerance of shrimp can be greatly improved. So it might provide an alternative method to reduce mortality, help to enhance resistance to pathogens and reduce the occurrence of infectious diseases. The significant positive genetic correlation between ST and body length suggested that ammonia is more toxic to shrimp in the early stage. The medium-strength genetic correlations of the ST and SS50 between the two environments (0.394±0.097 and 0.377±0.098, respectively) indicate a strong genotype-by-environment (G×E) interaction for ammonia tolerance between the different salinity levels. Therefore, salinity-specific breeding programs for ammonia tolerance in shrimp should be purposefully implemented.

Substituting fishmeal with mixtures of wheat, corn and soya bean meals in diets for the white leg shrimp, Litopenaeus vannamei (Boone): effect on production parameters and preliminary economic assessment

We analysed the effect on production and economic performance of juvenile Litopenaeus vannamei of isoproteic diets substituting fishmeal by 25%, 50%, 75% and 100% with mixtures of wheat, soya bean and cornmeals. In a laboratory trial, 10 juveniles m−2 (1.1 ± 0.1 g) were reared in 60-L plastic containers using a recirculation system for 90 days. Three replicates were used to test each diet. A commercial diet serving as a reference and the diet with the highest content of essential amino acids (50% substitution, 6.46 ± 1.1 g) produced significantly higher shrimp final weight (7.12 ± 0.9 g, P < 0.05). There were not significant differences in specific growth rate and mean survival (85.9 ± 0.2%, P > 0.05). In a pond trial, 10 shrimp m−2 (1.08 ± 0.3 g) were cultivated in 1.5 m−3 cages for 35 days, testing the diets in triplicate. Final weight was significantly higher (P < 0.05) when 100% substitution was used (10.89 ± 0.24 g), while survival did not differ significantly among diets (P > 0.05). The optimal level of substitution was estimated at 86.0%. Apparently, nutrients contained in the diets combined well with natural feed available in the pond, up to a point where 7.3% of fishmeal inclusion is recommended. An economic analysis showed that 100% substitution produced the best results. We conclude that mixtures of wheat, corn and soya meals are potential alternatives to replace fishmeal effectively in diets for L. vannamei.

Probiotic modulation of the gut bacterial community of juvenile Litopenaeus vannamei challenged with Vibrio parahaemolyticus CAIM 170

The protective effects of two probiotic mixtures was studied using the fingerprints of the bacterial community of Litopenaeus vannamei juveniles exposed to probiotics and challenged with Vibrio parahaemolyticus CAIM 170. Fingerprints were constructed using 16S rRNA gene and the PCR-SSCP (Single strand conformation polymorphism) technique, and the probiotics used were an experimental Bacillus mixture (Bacillus tequilensis YC5-2 + B. endophyticus C2-2 and YC3-B) and the commercial probiotic Alibio. The DNA for PCR-SSCP analyses was extracted directly from the guts of shrimps treated for 20 days with the probiotics and injected with 2.5×105 CFU g-1 of V. parahaemolyticus one week after suspension of the probiotic treatment. Untreated shrimps served as positive (injected with V. parahaemolyticus) and negative (not injected) controls Analysis of the bacterial community carried out after inoculation and 12 and 48 h later confirmed that V. parahaemolyticus was present in shrimps of the positive control , but not in the negative control or treated with the probiotic mixtures. A significant difference in the diversity of the bacterial community was observed between times after infection. The band patterns in 0-12 h were clustered into a different group from that determined after 48 h, and suggested that during bacterial infection the guts of whiteleg shrimp were dominated by gamma proteobacteria represented by Vibrio sp. and Photobacterium sp. Our results indicate that the experimental and the commercial mixtures are suitable to modulate the bacterial community of L. vannamei and could be used as a probiotic to control vibriosis in juvenile shrimp.

Implementation of the mixed linear models in experimental infections with WSSV in the withe shrimp Litopenaeus vannamei

The White Spot Syndrome Virus has been very detrimental for the shrimp industry. Up to date there is no cure for the disease, thus, it is necessary to implement reliable experimental strategies to evaluate the effect of drugs and the host response during the prognosis of the disease. In this study, we evaluated two ways of infection with WSSV (200 copies WSSV-DNA) (injection and immersion), at constant temperature (26 ± 0.5ºC), in juveniles of Litopenaeus vannamei (4.8 ± 0.38 g) in intermolt stage. In the infection by injection, the organisms were lethargic with reddish appearance 2 days after infection and mortality (100%) was observed within 2-5 days: 63% organisms with light degree of infection [20 copies of DNA &amp; 1-5 Cowdry A-type inclusions in hypertrophied nuclei (CAI)/200 fields], 21% had moderate infection (200 copies of DNA &amp; 1-2 CAI/20 fields) and 16% severely infected (2000 copies of DNA &amp; more than 10 CAI/field). No mortality was observed in the controls. In the infection by immersion, the signs of WSSV were observed 3 days after infection: 38% of mortality was observed during 3-9 days: 25% of the organism with light degree of infection (20 copies of DNA &amp; 1-2 CAI/20 fields), 5% moderately infected (200 copies of DNA &amp; 1-2 CAI/20 fields) and 8% with severe infection (2000 copies of DNA &amp; 1-5 CAI/2 fields. The other 62% organisms were necropsied at day 12 and tested positive to the WSSV-PCR (light infection = 20 copies of DNA), but did not show CAI by histology. No mortality was observed in the controls. For the statistical analysis, the data did not fit the criteria of independence and linearity needed for the analyses of variance, thus we used instead the mixed linear models and were able to observe a better prediction: in the injected organisms, the mortality reached the highest peak at day 5 after infection. In the organisms infected by immersion, the highest peak or mortality was observed at day 9 after infection. The analysis of variance of Kenward-Roger indicated significant differences between the days of mortality (F = 20.1, P = 0.001), as well as among the ways of infection (Random analysis) (P = 0.007).

The effects of different feeding rates and re-feeding of Litopenaeus vannamei in a biofloc culture system

The natural productivity in biofloc culture systems could be an important source of supplementary food to shrimp, representing savings in artificial feed. The aim of the present study was to evaluate the effects of using different feeding rates for a period of 21days with a posterior re-feeding period in a microcosm system in the presence of bioflocs. Litopenaeus vannamei juveniles (1.14±0.38g) were stocked at 400 shrimp m−3 in 150-L tanks in a biofloc recirculation system in two phases. The feeding rates were calculated considering an expected weekly growth of 1g week−1 and an estimated weekly mortality of 0.5%; each treatment corresponded to a different feeding rate, and each feeding rate corresponded to a fixed food conversion ratio. The first phase (food restriction) lasted 21days, and the following treatments were used: T0 (no artificial feed addition), T0.3, T0.6, T0.9, T1.2, T1.5, T1.8 and T2.1. In the second phase (re-feeding), the feeding rate was calculated based on the average of the best results in the first phase of the experiment (FCR=1.45). The re-feeding period lasted for more 29days. There were no observed significant differences in the water quality parameters among the treatments (P>0.05). At the end of the food restriction, the shrimp in T0, T0.3 and T0.6 presented lower final weights (P<0.05), and the weights in the other treatments did not significantly differ (P>0.05). The survival rate was lower only in T0 in the two phases of the study. The other treatments presented survival rates higher than 95%, with no significant differences among them. The feed intake did not increase during the re-feeding period, indicating that hyperphagia did not occur after a period of food restriction. The SGRs were higher for treatments that received lower amounts of feed in the first phase, and treatments T0, T0.3 and T0.6 presented partial weight compensation compared with the treatments with higher feeding rates. This study indicates that shrimp can be reared in a biofloc system with lower feeding rates, obtaining partial weight compensation and high survival rates and saving up to 24.79% of the artificial feed.