Effects of the probiotic Bacillus subtilis (BP11 and BS11) on the growth and survival of Pacific white shrimp,Litopenaeus vannamei

The effect of Bacillus S11 (BS11)‐ and/or Bacillus P11 (BP11)‐supplemented feeds on the growth performance, survival, immunoenhancement and disease resistance of cultured Pacific white shrimp, Litopenaeus vannamei, was evaluated. Four feeding treatments of (i) regular feed (control), (ii) BS11‐supplemented feed, (iii) BP11‐supplemented feed and (iv) BS11‐and BP11‐supplemented feed were prepared and used for shrimp cultivation in closed recirculating cement tanks (~400 L) in two trials, one for juvenile and PL‐30 shrimp at 60 and 90 days, respectively. The results showed that BS11 gave a higher probiotic potential than BP11 for both age groups of L. vannamei in cultivation, because the average weight and survival of shrimp fed BS11‐supplemented feed were significantly higher (P < 0.05) than those of the control and the other two groups. The survival of shrimp fed either BS11‐or both BS11‐and BP11‐supplemented feed was significantly higher (P < 0.05) than that of the control group. In addition, the highest total haemocyte and granular haemocyte counts and phenoloxidase activity were found in shrimp fed with the BS11‐supplemented feed. After challenge with Vibrio harveyi 639 (~10⁷ CFU mL^?1) by immersion, the lowest cumulative death (%) and disease resistance were clearly found in shrimp fed with the BS11‐supplemented feed.     

In vitro and in vivo selection of probiotic purple nonsulphur bacteria with an ability to inhibit shrimp pathogens: acute hepatopancreatic necrosis disease‐causing Vibrio parahaemolyticus and other vibrios

Shrimp cultivation has been faced with huge losses in productivity caused by infectious shrimp pathogenic vibrios, especially Vibrio parahaemolyticus that causes acute hepatopancreatic necrosis disease (AHPND). Hence, purple nonsulphur bacteria (PNSB) were isolated from shrimp ponds for investigating their abilities to control shrimp pathogenic Vibrio spp. and their use as probiotics for sustainable shrimp cultivation. Based on their probiotic properties, strains S3W10 and SS15 were selected because of their strong abilities to produce amylase, gelatinase and vitamin B12. However, only three PNSB strains (SS15, TKW17 and STW181) strongly inhibited V. harveyi_KSAAHRC and V. vulnificus_KSAAHRC including V. parahaemolyticusAHPND strains by secreting antivibrio compounds. Four selected PNSB also grew in the presence of pancreatic enzymes, and they were identified as Rhodobacter sphaeroides for strains S3W10, SS15 and TKW17 and Afifella marina for strain STW181. The effects of a mixed culture were also investigated as follows: T1 (S3W10 + SS15), T2 (S3W10 + TKW17) and T3 (S3W10 + STW181) on postlarval white shrimp (Litopenaeus vannamei) for 60 days by comparison with a control. All three probiotic PNSB sets significantly improved the digestive enzyme activities and shrimp growth with their proliferation in shrimp gastrointestinal tract although the shrimp survival was not significantly different. They also significantly reduced the cumulative mortality of shrimp exposed to a virulent AHPND strain (V. parahaemolyticusSR2). This is the first to conclude that selected probiotic PNSB strains have great potential to be used for shrimp cultivation to control vibrios including AHPND strains.     

Ingestion of food pellets containing Escherichia coli overexpressing the heat‐shock protein DnaK protects Penaeus vannamei (Boone) against Vibrio harveyi (Baumann) infection

Feeding aquatic animals with bacterial encapsulated heat‐shock proteins (Hsps) is potentially a new method to combat vibriosis, an important disease affecting aquatic animals used in aquaculture. Food pellets comprised of shrimp and containing Escherichia coli overexpressing either DnaK‐DnaJ‐GrpE, the prokaryotic equivalents of Hsp70‐Hsp40‐Hsp20, or only DnaK were fed to juveniles of the white leg shrimp Penaeus vannamei, and protection against pathogenic Vibrio harveyi was determined. Maintaining pellets at different temperatures for varying lengths of time reduced the number of live adhering E. coli, as did contact with sea water, demonstrating that storage and immersion adversely affected bacterial survival and attachment to pellets. Feeding P. vannamei with E. coli did not compromise their survival, indicating that the bacteria were not pathogenic to shrimp. Feeding P. vannamei with pellets containing bacteria overproducing DnaK (approximately 60 cells g^?1 pellets) boosted P. vannamei survival twofold against V. harveyi, suggesting that DnaK plays a role in Vibrio tolerance. Pellets containing DnaK were effective in providing protection to P. vannamei for up to 2 weeks before loss of viability and that DnaK encapsulated by these bacteria enhanced shrimp resistance against Vibrio infection.     

Effect of polysaccharides extracts of algae Ulva rigida on growth,antioxidant, immune response and resistance of shrimp,Litopenaeus vannamei against Photobacterium damselae

This study was carried out to investigate the effect of water‐soluble polysaccharides extract of algae Ulva rigida (WPU) as dietary supplement on growth performance, antioxidant enzyme activity, lysozyme and phenoloxidase activity, and resistance of shrimp (Litopenaeus vannamei) subjected to bacterial infection with Photobacterium damselae. Three replicate groups of shrimp (1.0 g) were fed four diets containing four levels, 0 or control, 0.5, 1 and 1.5 g/kg of WPU for 8 weeks over the growth trial. Thereafter, 30 shrimps from each dietary treatment were infected with bacteria P. damselae to evaluate disease resistance of infected shrimp. The results of this study showed that WPU was effective as a growth promoter for L. vannamei. The best growth rate was observed in shrimp fed 1.5 g/kg of WPU diet. Regarding antioxidant defences, the diets supplemented with three levels of WPU stimulated glutathione peroxidase and catalase activates in experimental shrimps. MDA content of L. vannamei‐fed diet containing WPU 1.5 and WPU 1.0 was lower than WPU 0 and WPU 0. 5 diets. Also, lysozyme and phenoloxidase activities of shrimp receiving WPU at 1.0 and 1.5 level were significantly higher than those fed WPU 0 and WPU 0.5 diets. In addition, using WPU extract in all diets decreased mortality in L. vannamei in a dose‐dependent manner after challenge with P. damselae. These results suggest that incorporation of water‐soluble polysaccharides from green algae U. rigida at 1.5 g/kg doses improves growth and antioxidant activity and enhances the immune responses in shrimp L. vannamei.     

The Effect of Probiotics in a Litopenaeus vannamei Biofloc Culture System Infected with Vibrio parahaemolyticus

We analyzed the effect of commercial bacterial probiotics on a Litopenaeus vannamei biofloc culture system infected with Vibrio parahaemolyticus. Three replicates of two experimental treatments were conducted: a control system (without probiotic) and a system with the application of a multistrain probiotic containing Bacillus spp., Enterococcus spp., Thiobacillus spp., and Paracoccus spp. applied to the water and another multistrain probiotic containing Bacillus spp., Enterococcus spp., and Lactobacillus spp. added to the feed. Growth and survival rate were significantly higher in the probiotic treatment group (P < 0.05), and the shrimp in the probiotic group also had a lower (P < 0.05) FCR compared to the shrimp in the control group (1.4 vs. 2.7).     

Vibrio spp. Control at Brine Shrimp,Artemia, Hatching and Enrichment

Experiments were conducted to evaluate different prophylactic methods to control the bacterial load in brine shrimp, Artemia, hatching. The first experiment evaluated three treatments to control Vibrio spp. during the Artemia hatching: microalgae (Chaetoceros calcitrans), probiotic (Bacillus spp.), and antibiotic (Florfenicol). In the second experiment, Artemia metanauplius were enriched in distinct treatments with C. calcitrans, probiotic, and emulsion rich in docosahexaenoic and eicosapentaenoic fatty acids. Enriched Artemia metanauplius and nauplii (control) were offered to white shrimp, Litopenaeus vannamei, postlarvae (PL₇–PL₁₉). Presumptive Vibrio were quantified in Artemia, PL, and rearing water. Microalgae and probiotic were effective to control Vibrio spp. in Artemia nauplii. The enrichment process increased the Artemia bacterial load but did not affect Vibrio load in L. vannamei.     

Evaluation of frozen Umbrella‐stage Artemia as first animal live food for Litopenaeus vannamei (Boone) larvae

An alternative larval shrimp feeding regime, in which umbrella‐stage Artemia were constituting the first zooplankton source was evaluated in the culture of Litopenaeus vannamei. In a preliminary experiment, umbrella‐stage Artemia were fed to larvae from zoea 2 (Z2) to mysis 2 (M2) stages to identify the larval stage at which raptorial feeding starts and to determine daily feeding rates. The following experiment evaluated the performance of two feeding regimen that differed during the late zoea/early mysis stages: a control treatment with frozen Artemia nauplii (FAN), and a treatment with frozen umbrella‐stage Artemia (FUA). The ingestion rate of umbrella‐stage Artemia increased from nine umbrella per larvae day^?1 at Z2 stage to 21 umbrella per larvae day^?1 at M2. A steep increase in ingestion and dry weight from Z3 to M2 suggests a shift to a raptorial feeding mode at the M1 stage. Treatment FUA exhibited a significantly higher larval stage index (P < 0.05) during the period that zoea larvae metamorphosed to the mysis stage, and a higher final biomass, compared with treatment FAN. Based on these results and on practical considerations, a feeding regime starting with umbrella‐stage Artemia from Z2 sub‐stage can be recommended for L. vannamei larvae rearing.     

Effect of probiotic (Bacillus spp.) addition during larvae and postlarvae culture of the white shrimp Litopenaeus vannamei

The effect of the addition of Bacillus probiotic during larvae and postlarvae culture of the white shrimp Litopenaeus vannamei was examined in three separate experiments: (I) Nauplius_4‐5 to Zoea₃, which were exposed to probiotic in the water (P_w), only in the microalgae (P_m), in the water and microalgae (P_wm) and a control with no probiotic (C); (II) Mysis₁ to Mysis₃, which were exposed to probiotic in the water (P_w), only in Artemia (P_a), in the water and Artemia (P_wa) and a control (C); (III) PL₁ to PL₁₀, which were exposed to similar treatments for mysis experiment. The use of probiotic Bacillus spp. resulted in an increase in the survival and growth of zoea and mysis phases, especially when the probiotic was added only in the water. For postlarvae, the use of the probiotic had no influence on the zootechnical parameters, however, there was a reduction in the count of presumptive Vibrio both for water and shrimp.     

Effects of dietary β‐glucan and glycyrrhizin on non‐specific immunity and disease resistance of white shrimp,Litopenaeus vannamei (Boone) challenged with Vibrio alginolyticus

The white shrimp Litopenaeus vannamei, fed immunostimulant‐free, 0.2%β‐glucan and 0.06% glycyrrhizin diets for 18 days, respectively, were challenged with Vibrio alginolyticus at 6.4 × 10⁴ CFU shrimp^?1. The total haemocyte count (THC), phenoloxidase (PO) activity, respiratory burst (RB) and superoxide dismutase (SOD) activity changes for a 120‐h period were investigated, and shrimp mortality was also recorded. The results showed that PO activity, RB and SOD activity were significantly higher in shrimp fed the two immunostimulant diets after 18 days than those in shrimp fed immunostimulant‐free diets. The THC and SOD activity decreased significantly from 0 to 24 h post challenge, and then reverted to normal levels at 96 and 72 h respectively. The values for PO activity and RB increased from 0 to 48 h post challenge. Compared with those fed the control diets, shrimp fed immunostimulants had significantly higher PO activity and RB values at 120 h post challenge. Mortalities after challenge with V. alginolyticus were significantly lower in shrimp fed with β‐glucan or glycyrrhizin than in those fed with a diet without immunostimulants. It was concluded that dietary β‐glucan and glycyrrhizin increased the shrimp immunity. Furthermore, β‐glucan caused an increase in some immune parameters 12 h earlier than glycyrrhizin after V. alginolyticus challenge.     

凡纳滨对虾肠道内产消化酶益生菌的分离与筛选

为获得具有消化酶活性且安全的益生菌,从凡纳滨对虾肠道中初步分离得到576株细菌,对菌株进行产蛋白酶、淀粉酶和脂肪酶能力的定性及定量测试,筛选出产酶种类多且产酶能力强的菌株11株。对筛选出的11株菌进行了幼虾浸浴实验、药敏性实验和溶血性实验,以评价其生物安全性。将11株菌的菌悬液添加到凡纳滨对虾幼虾的养殖水体中进行浸浴实验,浸浴结束后用鳗弧菌进行刺激,测定不同浸浴组幼虾相关免疫基因的相对表达量,以确定其对幼虾的保护效果。综合消化酶活性、菌株对幼虾的保护效果及生物安全性,筛选得到4株效果较好的菌株。菌株的16S r DNA分子鉴定结果表明,细菌1号、2号和4号分别与芽孢杆菌(Bacillus sp.PCSAS2-38,GQ284495.1)、蜡样芽孢杆菌(B.cereus strain N419,JN400121.1)及苏云金芽孢杆菌(B.thuringiensis strain EA26.1,KC758847.1)的相似性均为100%,9号菌株与荚膜红细菌(Rhodobacter capsulatus strain PSB-03,FJ866782.1)相似性达到99%,为后续益生菌制剂的开发奠定了前期基础。     

Successful rearing of whiteleg shrimp Litopenaeus vannamei larvae fed a desiccation‐tolerant nematode to replace Artemia

The nematode Panagrolaimus sp. was tested as live feed to replace Artemia nauplii during first larval stages of whiteleg shrimp Litopenaeus vannamei. In Trial 1, shrimp larvae were fed one of four diets from Zoea 2 to Postlarva 1 (PL1): (A) Artemia nauplii, control treatment; (NC) nematodes enriched in docosahexaenoic acid (DHA) provided by the dinoflagellate Crypthecodinium cohnii; (N) non‐enriched nematodes; and (Algae) a mixture of microalgae supplemented in C. cohnii cells. In Trial 2, shrimp were fed (A), (NC) and a different treatment (NS) with nematodes enriched in polyunsaturated fatty acids (PUFAs) provided by the commercial product S.presso^®, until Postlarva 6 (PL6). Mysis 1 larvae fed nematodes of the three dietary treatments were 300 μm longer (3.2 ± 0.3 mm) than control larvae. At PL1, control shrimp were 300 μm longer (4.5 ± 0.3 mm) than those fed DHA‐enriched or PUFAs‐enriched nematodes. No differences were observed in length and survival at PL6 between control larvae and those fed DHA‐enriched nematodes (5.1 ± 0.5 mm; 33.1%–44.4%). Shrimp fed microalgae showed a delay in development at PL1. This work is the first demonstration of Panagrolaimus sp. suitability as a complete substitute for Artemia in rearing shrimp from Zoea 2 to PL6.     

Effects of Dietary Administration of Probiotic Halomonas sp. B12 on the Intestinal Microflora,Immunological Parameters,and Midgut Histological Structure of Shrimp,Fenneropenaeus chinensis

The experiment was conducted to investigate the effects of oral administration of probiotic Halomonas sp. B12 (previously isolated from the intestine of Fenneropenaeus chinensis) on the intestinal microflora, immunological parameters, and midgut histological structure of F. chinensis. Shrimp (initial weight: 4.00 ± 0.10 g) were fed diets containing Halomonas sp. B12 at 0 (control), 3.68 × 10⁷ (T1), and 7.18 × 10¹⁰ (T2) colony‐forming units per gram for 6 wk, respectively. The results showed that the total bacterial counts significantly increased (P < 0.05) with supplementation of dietary probiotic B12. However, Vibrio spp. counts significantly decreased (P < 0.05) in the intestine of shrimp with increasing dietary probiotic B12. Hemocyte counts in the shrimp fed the diets supplemented with probiotic B12 were significantly higher (P < 0.05) than the control group. Both phenoloxidase (PO) activity in plasma and hemocyte lysate supernatant were higher in the shrimp fed diets supplemented with probiotic B12 compared with the control group. No significant difference was found in PO activity in plasma between the T1 and the control (P > 0.05). PO activity in plasma was higher in T2 than that in T1. Cumulative shrimp mortality after 10‐d white spot syndrome virus (WSSV) challenge test significantly decreased with increasing dietary probiotic B12 (P < 0.05). No significant difference was found between T1 and control in cumulative shrimp mortality after challenge test (P > 0.05). The oral administration of probiotic B12 to F. chinensis was beneficial to protect the integrity of shrimp intestinal mucosal layer. In summary, even though the low dose (T1) had some effects on bacterial counts and immunological parameters, only the high dose (T2) significantly increased the resistance of the shrimp to WSSV.     

Oral Administration of Hot‐water Extract of Tropical Brown Seaweed,Sargassum cristaefolium,to Enhance Immune Response,Stress Tolerance,and Resistance of White Shrimp,Litopenaeus vannamei,to Vibrio parahaemolyticus

The efficacy of hot‐water extract of tropical brown seaweed, Sargassum cristaefolium (SCE), supplemented in diets on immune response, stress tolerance, and disease resistance of Litopenaeus vannamei to Vibrio parahaemolyticus was evaluated. Shrimp were fed diets containing graded levels of SCE (0, 250, 500, 750, and 1000 mg/kg). The results showed that shrimp fed all diets containing SCE had significantly higher (P < 0.05) immune response in total hemocyte count (THC), differential hemocyte count (granular and hyaline cells), and phagocytic activity than those of shrimp fed the control diet. Similarly, in low dissolved oxygen stress tolerance test and the challenge test with V. parahaemolyticus, survival rates of shrimp fed all diets containing SCE were significantly higher (P < 0.05) (83–93% in stress test and 27–47% in challenge test) than those of shrimp fed the control diet (77 and 3.3%, respectively). These results suggest that oral administration of SCE at 500 and 750 mg/kg can be effectively used to enhance immune response, stress tolerance, and resistance of white shrimp, L. vannamei, against V. parahaemolyticus infection. These findings also confirm that using dietary SCE as immunostimulant is effective at increasing the nonspecific immune system in penaeid shrimp, L. vannamei.     

Effects of Lactobacillus pentosus on the growth performance,digestive enzyme and disease resistance of white shrimp,Litopenaeus vannamei (Boone, 1931)

The objective of this study was to evaluate the probiotic properties of lactic acid bacteria (LAB) strains isolated from digestive tract of white shrimp Litopenaeus vannamei. Eighteen LAB colonies were isolated and one bacterium was found capable of producing three extracellular enzymes (protease, cellulose and lipase) simultaneously and exhibited antagonistic activity against shrimp pathogens (Vibrio vulnificus, V. rotiferianus and V. campbellii). The putative probiotic strain AS13 was identified as Lactobacillus pentosus based on 16S rRNA sequencing. The L. vannamei were fed diet containing 0 (control), 10⁶, 10⁷ and 10⁸ CFU g^?1 bacterial cells of AS13 for 28 days. The results showed that supplementation of L. pentosus significantly improved the growth performance and feed utilization in the treated groups over the control. Similarly, digestive enzyme activities were elevated in the intestines of treated groups. Moreover, feeding of supplemented diets containing AS13 significantly reduced the mortality rate caused by pathogenic Vibrio species (V. vulnificus, V. rotiferianus and V. campbellii). Our results indicated L. pentosus AS13 addition at 10⁷ CFU g^?1 can effectively enhance the growth performance, feed utilization, digestive enzymes and disease resistance of L. vannamei in the laboratory condition.     

Effects of synbiotic containing Lactobacillus plantarum 7–40 and galactooligosaccharide on the growth performance of white shrimp,Litopenaeus vannamei

This study aimed to develop a synbiotic combination with probiotic, Lactobacillus plantarum 7–40 and one of three prebiotics, fructooligosaccharide (FOS), galactooligosaccharide (GOS) and mannan oligosaccharide (MOS). The best in vitro growth was observed when probiotic was cultured in the medium containing either FOS or GOS as the sole of carbon source. The analysis of enzyme activity revealed that GOS induced the highest activities of protease and β‐galactosidase of probiotic. Based on the findings, probiotic + GOS were selected as synbiotic to evaluate if it could promote the growth of white shrimp, Litopenaeus vannamei. For this, four diets, including a basal diet with no GOS or probiotic (control), 0.4% GOS (PRE), 10⁸ CFU probiotic kg^?1 (PRO) and 0.4% GOS in combination with 10⁸ CFU probiotic kg^?1 (SYN), were fed to shrimp for 60 days, and then the growth performance, intestinal microbiota (including total Vibrio counts, VBCs; and lactic acid bacteria, LAB) and digestive enzyme (including protease, leu‐aminopeptidase and β‐galactosidase) were evaluated. The weight gain (WG) of shrimp fed the PRO did not significantly differ from those of control (p > .05). Shrimp fed the SYN had significantly higher WG compared with the other treatments (p < .05). In addition, the SYN‐fed shrimp had significantly higher LAB and protease, leu‐aminopeptidase and β‐galactosidase activity (p < .05). The lowest presumptive Vibrio count (VBC) was also observed in intestines of SYN‐fed shrimp. Therefore, we suggested that Lac. plantarum 7–40+ GOS can be used as a synergistic synbiotic for shrimp culture.     

Effects of polysaccharides from mycelia of Cordyceps sinensis on growth performance,immunity and antioxidant indicators of the white shrimp Litopenaeus vannamei

Studies were conducted to evaluate polysaccharides from mycelia of Cordyceps sinensis (PMCS) as a feed additive for pacific white shrimp (Litopenaeus vannamei). Shrimps were randomly divided into two groups. One group received the PMCS‐supplemented diet for 52 days, and the other group received no treatment. The data showed that shrimps given PMCS gained more body weight compared with the control group (P < 0.05). Haemolymph immunity indicators, including phenoloxidase (PO), alkaline phosphatase (ALP), acid phosphatase (ACP) and lysozyme (LSZ), were remarkably greater in the PMCS group (P < 0.05). In addition, antioxidant parameters, including superoxide dismutase (SOD), glutathione reduced form (GSH), reactive oxygen species (ROS) and total antioxidant capacity (TAC), were significantly greater in the treatment group. However, there were no significant differences in malondialdehyde (MDA) levels and glutathione peroxidase (GSH‐PX) activity between the control and treatment groups. Moreover, the number of Vibrio ichthyoenteri was less in the group treated with PMCS (P < 0.05). In conclusion, PMCS can be used to improve the growth performance and health of pacific white shrimp.     

Effect of dietary supplementation with Bacillus subtilis on the growth,performance, immune response and antioxidant activities of the shrimp (Litopenaeus vannamei)

The objective of this study was to evaluate the effect of dietary supplementation of a probiotic bacterium, Bacillus subtilis, on the growth, immune response and antioxidant activities of shrimp (Litopenaeus vannamei). Shrimps with an average initial weight of 2.11±0.17 g were randomly assigned to four groups with three replicates. The control group was fed a basal diet, and three treated groups were fed diets supplemented with B. subtilis at doses of 1 × 10⁴, 5 × 10⁴ and 10 × 10⁴ colony‐forming unit (CFU) g^?1 feed respectively. After 40 days of culture, 10 shrimps from each replicate were taken randomly for the determination of immune response and oxidization resistance indices. The results showed that the shrimps fed with B. subtilis at a dose of 1 × 10⁴, 5 × 10⁴ CFU g^?1 feed showed significantly better growth than that of the control diet. The phenoloxidase activities showed a tendency to increase with an increased dose of B. subtilis in diets but there was no significant difference among the three treated groups. In addition, phenoloxidase activities were found to be significantly higher (P<0.05) in the groups treated with B. subtilis than that of the control group. Shrimps treated with 5 × 10⁴ CFU g^?1 feed probiotic bacterium showed the highest lysozyme activity and it was significantly higher (P<0.05) than the other groups. However, there was no significant difference in acid phosphatase and alkaline phosphatase activity across all the groups. The total antioxidant capacity, superoxide dismutase and glutathione peroxidase activities in the probiotic‐treated groups were significantly increased (P<0.05) as compared with the control groups. Both maleic dialdehyde concentration and superoxide anion activities in the probiotic‐treated groups were significantly lower (P<0.05) than those of the control. The probiotic did not affect the nitric oxide synthase and the catalase activity in any of the control and treated groups. These results indicated that the probiotic B. subtilis could significantly promote the growth rate of shrimp by increasing the immune function and antioxidant capacity. The most effective dose of B. subtilis in the diet was 5 × 10⁴ CFU g^?1 feed.     

Survival of Post‐larval Litopenaeus vannamei Following Acclimation to Low Salinity Waters at Different Temperatures

Temperature and salinity are two factors known to influence the growth potential and survival of the Pacific white shrimp, Litopenaeus vannamei, acclimated to low salinity waters. In west Alabama, farmers suspect low water temperatures at stocking, in conjunction with low salinity and suboptimal ionic profiles, might be responsible for reduced survival and production at harvest. To determine the influence of temperature and salinity on post‐larval (PL) L. vannamei, a series of bioassays were conducted at the E.W. Shell Fisheries Research Station in Auburn, Alabama and Claude Peteet Mariculture Center in Gulf Shores, Alabama. PL L. vannamei of ages 11, 13, and 20 (PL₁₁, PL₁₃, and PL₂₀) were acclimated down to salinities of 12, 4, 2, 1, 0.5, and 0.2 ppt at different temperatures ranging from 17.6 to 24.0 C. During the acclimation bioassays survivals were assessed at 24 and 48 h. PL survival of the three age groups examined were significantly reduced at salinities of 1, 0.5, and 0.2 ppt. These results correspond well to those reported at higher temperatures confirming that across the tested temperature range salinity endpoint was the driving factor in determining survival and that suboptimal temperatures had a minimal influence on survival.     

Immune Responses and Resistance against Vibrio parahaemolyticus Induced by Probiotic Bacterium Arthrobacter XE-7 in Pacific White Shrimp, Litopenaeus vannamei

A 63-d feeding experiment was conducted to determine the effects of dietary supplementation of probiotic bacterium Arthrobacter XE-7 on immune responses and resistance against Vibrio parahaemolyticus in the Pacific white shrimp, Litopenaeus vannamei . The probiotic bacteria were administered orally at four different doses of 0, 10⁶, 10⁸, and 10¹⁰ colony-forming unit (CFU)/g feed for shrimp. On Day 50, the shrimp were challenged with Vibrio parahaemolyticus by bath. On Days 7, 21, 49, and 63, six shrimp per tank were sampled to take intestine and hemolymph. With increasing dietary supplementation of probiotic bacteria, shrimp mortality decreased from 63.16% (the control) to 55.9% (10⁶ CFU/g feed), 51.75% (10⁸ CFU/g feed), and 51.78% (10¹⁰ CFU/g feed), respectively. Vibrio counts in intestine of shrimp fed probiotic bacterium Arthrobacter XE-7 was generally lower than that in the control shrimp ( P  < 0.05). The probiotic bacteria generally increased the immune parameters in shrimp, that is, total hemocyte counts, percentage phagocytosis, respiratory burst activity, and serum phenoloxidase activity. The results showed that probiotic bacterium Arthrobacter XE-7 can be used as probiotic in shrimp feed.     

Dietary administration of soybean isoflavones enhances the immunity of white shrimp Litopenaeus vannamei and its resistance against Vibrio alginolyticus

The growth response, total hemocyte count (THC), respiratory burst (release of superoxide anion), phenoloxidase (PO) activity, superoxide dismutase (SOD) activity, nitric oxide synthase (NOS) activity and resistance to the pathogen Vibrio alginolyticus were measured in white shrimp (Litopenaeus vannamei) which had been fed diets supplemented with soybean isoflavones (SI) at 0, 5, 10, 20, 40 mg kg^?1 feed for 8 weeks. Dietary SI had no significant influence on survival rate of the shrimp. Significantly greater SGR was observed in treatments with 10, 20 and 40 mg kg^?1 SI supplement than that in control (P < 0.05). Shrimp fed a diet with 20 mg kg^?1 SI showed significant increase in THC, PO activity, respiratory burst activity, SOD activity as well as NOS activity (P < 0.05). Increased THC, respiratory burst activity, SOD activity and NOS activity were also noticed in shrimp fed SI at 10 or 40 mg kg^?1 (P < 0.05). Significant lower cumulative mortality after challenge was observed in shrimp fed diets with SI supplement (10.0–13.3%) than that in control group (36.7%) (P < 0.05). It is therefore concluded that oral administration of SI at 20 mg kg^?1 for 8 weeks could enhance the immune ability of shrimp and improve production in shrimp farming.