Probiotic applications for rainbow trout (Oncorhynchus mykiss Walbaum) II. Effects on growth performance,feed utilization,intestinal microbiota and related health criteria postantibiotic treatment

The effect of dietary probiotics (Bacillus subtilis, Bacillus licheniformis and Enterococcus faecium) was assessed on rainbow trout (Oncorhynchus mykiss Walbaum) previously treated with oxolinic acid. After feeding on supplemented diets for 10 weeks growth performance, feed utilization, gastrointestinal colonization and health status were assessed. B. subtilis + B. licheniformis fed fish displayed a significant improvement of feed conversation ration (FCR), specific growth rate (SGR) and protein efficiency ratio (PER). High levels of probiotic species were observed in the posterior gastrointestinal tract as transient digesta associated populations and potentially resident mucosal populations. Levels of Bacillus spp. reached log 3.74 CFU g^?1 on the mucosal epithelium and log 7.41 CFU g^?1 in the digesta of fish fed diets supplemented with B. subtilis and B. licheniformis. Enterococci levels reached log 2.84 CFU g^?1 on the mucosa and log 7.78 CFU g^?1 in the digesta of fish fed E. faecium supplemented diets. Feeding trout the Bacillus probionts alone or synergistically with E. faecium resulted in elevated leucocyte levels. The results of the current study demonstrate a potential role of probiotics for stabilizing/reinforcing the gastrointestinal microbiota after antibiotic treatment. This could reinvigorate the intestinal defensive barrier mechanism and provide protection against secondary potential pathogens.     

Effects of dietary probiotic on the growth performance,non‐specific immunity and disease resistance of cobia,Rachycentron canadum

The present study was performed to investigate the effects of a commercially available probiotic product (compound probiotic) containing Bacillus subtilis 7.0 × 10⁹ CFU g^?1, Bacillus licheniformis 3.0 × 10⁹ CFU g^?1, Lactobacillus spp. 5.0 × 10⁸ CFU g^?1 and Arthrobacter spp. 1.0 × 10⁸ CFU g^?1 on the growth performance, non‐specific immunity and protection against Vibrio harveyi infection in cobia (Rachycentron canadum). Fish were fed diets containing six graded levels of compound probiotic (0.0, 1.0, 2.0, 3.0, 4.0 and 5.0 g kg^?1) for 8 weeks. The results showed that the survival rate ranged from 81.1% to 84.4% with no significant difference among dietary treatments (P > 0.05) after feeding experiment. Dietary compound probiotic significantly increased the specific growth rate (SGR), serum lysozyme, alternative complement pathway (ACP) activity, phagocytosis percentage (PP) and respiratory burst activity of head‐kidney macrophages of cobia. Moreover, feeding of supplemented diets containing compound probiotic resulted in significantly lower mortality against the pathogens Vibrio harveyi compared with the control group. To elevate the growth and immune resistance ability of cobia, an optimal dose of dietary compound probiotic administration determined by second‐order polynomial regression analysis was 3.3 g kg^?1, on the basis of the SGR and mortality after challenge with V. harveyi.     

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.     

Effect of light limitation on the water quality,bacterial counts and performance of Litopenaeus vannamei postlarvae reared with biofloc at low salinity

The aim of this study was to evaluate the effect of light limitation on the water quality, bacterial counts and performance of Litopenaeus vannamei postlarvae reared with biofloc at low salinity (≈9 g L^?1). Two treatments were designed: T₁ = culture with natural sunlight and T₂ = culture in darkness. After 28 days, in both treatments, the final weight of shrimp was over 0.6 g with a specific growth rate over 7.4% d^?1, and a survival rate over 70%. In both treatments, Vibrio sp. concentration presented low values (culture with natural sunlight = 0.1 to 9.9 × 10² CFU mL^?1, culture in darkness = 0.4 to 11.7 × 10² CFU mL^?1) and Bacillus sp. had high values (culture with natural sunlight = 0.7 to 66.0 × 10⁴ CFU mL^?1, culture in darkness = 0.7 to 65.8 × 10⁴ CFU mL^?1). All water quality parameters remained within the ranges suitable for shrimp culture, except for alkalinity during the first stage of the study. Although in some sampling periods some significant differences were found in bacterial counts and water quality parameters, shrimp productive performance under culture with biofloc at low salinity was not affected significantly by light limitation.     

Effect of Lactobacillus acidophilussupplementation on growth performances,digestive enzyme activities and gut histomorphology of striped catfish (Pangasianodon hypophthalmusSauvage, 1878) juveniles

The influence of dietary supplementation of Lactobacillus acidophilus, on growth performance, digestive enzyme activities, gut histomorphology and gut microflora were evaluated in juveniles striped catfish (Pangasianodon hypophthalmus). Five experimental diets were formulated by supplementing 0, 10³, 10⁵, 10⁷ and 10⁹ CFU/g L. acidophilus in fishmeal and casein‐based semi‐purified diet. Triplicate groups of striped catfish (21.69 ± 0.18 g) were stocked in 15 fiberglass tanks with stocking density of 25 individuals per tank and fed twice daily at 2.5% of the fish body weight for 12 weeks. Weight gain, specific growth rate, feed conversion ratio and the protein efficiency ratio were significantly higher in fish fed with 10⁵ and 10⁷CFU/g L. acidophilussupplemented diets compared with the other treatment groups. Compared with the control and fish fed low (10³ CFU/g) L. acidophilus supplementation, those fed with 10⁵ and 10⁷ CFU/g had significantly higher (p < 0.05) apparent protein digestibility. Inclusion of L. acidophilus at 10⁷ CFU/g diet significantly increased amylase, protease and lipase activities. Microscopic analysis showed that the villi length in both the anterior and posterior gut and microvilli length in the posterior gut increased significantly in fish fed L. acidophilus supplementation at 10⁵ and 10⁷ CFU/g of diet. The fish fed L. acidophilus supplemented diets significantly increased the total lactic acid bacteria counts in the gut of striped catfish compared with the control‐fed group. Based on gut histomorphology and growth performance, inclusion of L. acidophilus at 10⁵ CFU/g appears to have the most positive effect on striped catfish farming.     

Dietary administration of Bacillus (B. licheniformis and B. subtilis) and isomaltooligosaccharide influences the intestinal microflora,immunological parameters and resistance against Vibrio alginolyticus in shrimp,Penaeus japonicus (Decapoda: Penaeidae)

The experiment was conducted to investigate the effects of oral administration of probiotics (Bacillus licheniformis and Bacillus subtilis) in combination with prebiotic isomaltooligosaccharide (IMO) on the intestinal microflora and immunological parameters of Penaeus japonicus and its resistence against Vibrio alginolyticus. A basal diet was supplemented with 0% probiotics and prebiotic (control), 10⁸ colony forming unit (CFU) g^?1B. licheniformis and 0.2% IMO (T1), 10⁸ CFU g^?1B. subtilis and 0.2% IMO (T2), 10⁸ CFU g^?1B. licheniformis in combination with 10⁸ CFU g^?1B. subtilis and 0.2% IMO (T3). The results showed that the total bacterial counts significantly increased (P<0.05) and Vibrio counts significantly decreased (P<0.05) in the intestine of shrimp with supplementation of dietary synbiotics. Shrimp fed the diet with both Bacillus probiotics and IMO (T3) produced significantly higher immune parameters (phenoloxidase activity, lysozyme activity and nitric oxide synthase activity and superoxide dismutase activity) than the control group (P<0.05). Significant lower cumulative mortality after challenge with V. alginolyticus was also observed in shrimp fed diet with both Bacillus probiotics and IMO (T3) than that in the control group (P<0.05). The results indicated that the oral administration of probiotics (B. licheniformis and B. subtilis) and prebiotic IMO has positive effects on bacterial flora in P. japonicus gut, and can activate non‐specific immunity of shrimp.     

The use of probiotics during the nursery rearing of the pink shrimp Farfantepenaeus brasiliensis (Latreille, 1817) in a zero exchange system

The present work evaluated the use of probiotics during the nursery rearing of the pink shrimp Farfantepenaeus brasiliensis, in a zero exchange aerobic heterotrophic culture system during 30 days. Three replicate tanks were randomly assigned to the following treatments: (1) Bacillus spp. mixture (Sanolife Pro‐‐W^®), (2) Bacillus sp., Enterococcus sp., Lactobacillus spp. mixture (Biomin Start‐grow^®), (3) Bacillus cereus var. toyoi and (4) control treatment (without probiotic addition). Bacteriological analysis monitored the abundance of presumptive Vibrio spp. in the water of experimental tanks. For the immunological analysis, shrimp haemolymph was collected to determine the granular haemocyte count and total protein concentration. Results showed that mean final weight and specific growth rate of shrimp in the probiotic treatments were significantly higher. Furthermore, shrimp reared in the probiotic treatments showed higher levels of total protein and granular haemocyte. The bacteriological analysis showed that the concentration of Vibrio spp. measured in probiotic treatment tanks was lower than that recorded in the control tanks.     

The effect of different carbon sources on the nutritional value of bioflocs,a feed for Macrobrachium rosenbergii postlarvae

A 15‐day lab‐scale experiment was performed to determine the possible use of bioflocs as a feed for Macrobrachium rosenbergii postlarvae. The bioflocs were grown on acetate, glycerol and glucose. A glycerol‐fed reactor was initially inoculated with a Bacillus spores mixture. The highest protein content was obtained in the (glycerol+Bacillus) bioflocs, i.e. 58±9% dry weight (DW). The glycerol and acetate bioflocs showed a lower, but similar content (42–43% DW) and glucose bioflocs contained 28±3% DW. Higher total n‐6 fatty acid contents were observed in the glycerol and (glycerol+Bacillus) bioflocs. The vitamin C content was variable, up to 54 μg ascorbic acid g^?1 DW in the glycerol bioflocs. Bioflocs were fed to M. rosenbergii postlarvae as the sole feed. High survival levels were obtained in the (glycerol+Bacillus) and glucose groups, i.e. 75±7% and 70±0% respectively. This was significantly higher than the starvation control (0% survival after 15 days). This indicated that the prawns were able to feed on the bioflocs. These results are in accordance with the biofloc's nutritional parameters and suggest that the choice of the carbon source used for growing bioflocs is of prime importance.     

凡纳滨对虾白便综合征发生与环境因子、机体免疫酶活性和微生物的相关性

为系统解析凡纳滨对虾白便综合征 (white feces syndrome,WFS)的发生与环境因子、微生物因子、宿主免疫力和水体微生物群落组成的关系。实验利用水体理化因子、可培养细菌、对虾机体免疫酶活性以及高通量测序等检测技术对健康与患WFS的池塘养殖凡纳滨对虾进行比较分析。结果显示,与健康组相比,患病池塘的水温、溶解氧 (DO)、pH、盐度等水质理化因子波动趋势相似,波动范围分别为26.1~29.0 °C、4.26~6.08 mg/L、8.39~8.73和40~49,患病组DO和盐度比健康组高;健康组对虾肝胰腺内可培养细菌和弧菌含量为1.19×10⁵~7.70×10⁵和8.8×10³~1.96×10⁴ CFU/g,弧菌占比为2%~16%,患病组对虾肝胰腺内可培养细菌和弧菌含量在3.80×10⁵~2.51×10⁶和2.02×10⁵~1.49×10⁶ CFU/g范围内,比健康组高15~113倍,弧菌占比在55%~70%。碱性磷酸酶 (AKP)、酸性磷酸酶 (ACP)、溶菌酶 (LZM)、超氧化物歧化酶 (SOD)和酚氧化酶 (PO)活性在健康组内为1.21~5.64、9.17~15.25、3.56~7.43、4.83~6.70及3.10~4.55 U/mg,在患病组内为2.12~5.39、19.22~26.96、19.73~26.85、3.00~4.14及7.76~9.21 U/mg。比较分析表明,WFS的发生与可培养细菌含量、弧菌占比、ACP、LZM、PO的相关性较强。高通量测序分析表明,患病组水体菌群结构的Ace和Chao指数呈一定程度下降趋势,PCoA指数偏离度较高,放线菌门、变形菌门相对丰度降低,拟杆菌门、蓝藻门相对丰度显著升高;RDA关联分析表明,盐度、溶解氧、虾体细菌、虾体弧菌、水体细菌是影响患病对虾水体菌群结构组成的重要因子。相关研究结果为解析养殖生产中对虾WFS发生机制提供数据支撑,并为WFS的临床防控奠定理论基础。     

Effect of amylase on growth,survival and proximate composition of the Polychaete,Perinereis cultrifera (Grube, 1840)

The effect of amylase on growth performance, survival rate and proximate composition of Perinereis cultrifera was investigated. The amylase produced by Bacillus sp. was added to polychaete basal diets at three concentrations such as 50, 100 and 150 mg kg^?1 in experiments I, II and III, respectively. After 90 days, polychaete receiving the diets supplemented with enzymes at 150 mg kg^?1 showed significantly better growth performance and survival rate than those fed the basal diet (Control). Among these experimental animals, the maximum protein, lipid, carbohydrate and ash contents were recorded in experiment III, whereas moisture content was maximum in control and minimum in experiment III. The essential fatty acids such as palmitic acid (C16:0), margaric acid (C17:0), stearic acid (C18:0) and arachidonic acid (C20:4ω‐6) occurred at higher concentration in experiment group than in control. Thus, the amylase produced by Bacillus sp. significantly influenced growth, survival rate and proximate composition of P. cultrifera which has importance in aquaculture industry.     

Potential of indigenous Bacillus spp. as probiotic feed supplements in an extruded low‐fish‐meal diet for juvenile olive flounder,Paralichthys olivaceus

A 12‐week feeding trial was designed to assess the probiotic potential of indigenous Bacillus amyloliquefaciens and/or Bacillus subtilis singly or in combination with Bacillus licheniformis in an extruded feed for olive flounder (Paralichthys olivaceus) juveniles. A high fish meal (FM) diet (control) and a low‐FM diet containing an alternative protein blend (30% FM replacement, FM30) were formulated. Three other experimental diets were prepared by inclusion of B. amyloliquefaciens (BA), B. subtilis (BS), or a mixture of B. amyloliquefaciens, B. subtilis, and B. licheniformis (BASL) into FM30 diet, with a final concentration of 10⁶ CFU/g diet. Results indicated that the FM30 diet was well tolerated by flounder, and the overall performance was not affected by dietary treatments. Lysozyme activity and total immunoglobulin level were significantly reduced in flounders when fed with the FM30 diet compared with the BASL and BA diets, respectively. The Bacillus additives neither enriched the relative abundance of the corresponding Bacillus spp. in the relevant gut microbiota of olive flounder nor modulated the presumptive gene functions of the gut microbiome. Despite the absence of growth‐promoting effect, the tested probiotics could still be economically viable for use as immunostimulants in commercial flounder diets with partial FM replacement.     

Effect of dietary supplementation of inulin and W. cibaria on haemato‐immunological parameters of hybrid surubim (Pseudoplatystoma sp)

The dietary supplementation of prebiotics, probiotics and symbiotic in hybrid surubins (a Pseudoplatystoma corruscans and P. fasciatum cross) was evaluated for the effects on their autochthonous intestinal microbiota and on haematological and immunological parameters. A total of 160 fish were divided into four treatment groups with four replicates each. The treatment groups were fed with the following diets for 15 days: control diet without supplementation; 0.5% inulin (prebiotic) supplementation; Weissella cibaria (CPQBA 001‐10 DRM 02) (7.87 ± 0.2 log CFU g^?1) supplementation; or 0.5% inulin and W. cibaria supplementation (symbiotic group). The midgut intestines of the fish with the symbiotic diet supplementation had higher concentrations of lactic acid bacteria (7.07 ± 1.11 log CFU g^?1) and low levels of Vibrio spp (1.90 ± 0.60 log CFU g^?1) and Pseudomonas spp (2.23 ± 1.48 log CFU g^?1). In addition, increased erythrocytes and reduced circulating neutrophils were observed in this group. No differences in blood glucose, serum protein or lysozyme levels were detected between treatment groups. However, a higher concentration of total immunoglobulin was observed in fish fed with the probiotic and symbiotic diets. The addition of 0.5% inulin (prebiotic) thus W. cibaria (probiotic) to the diet of Pseudoplatystoma hybrid surubins reduce the number of pathogenic bacteria and stimulate the beneficial intestinal microbiota and may possibly alter their immune defence system.     

Detection and Distribution of Flavobacterium columnare in Experimentally-Infected Channel Catfish,Ictalurus punctatus Using Culture and Polymerase Chain Reaction

Abstract

The authors examined the use of culture and polymerase chain reaction (PCR) to detect Flavobacterium columnare in experimentally-infected channel catfish, Ictalurus punctatus. Five treatments were utilized which included immersion exposure to 10⁶, 10⁷, 10⁸ colony forming units (CFU)/mL for 30 minutes, intramuscular injection of 10⁸ CFU/fish and a negative control (i.e., immersion in Cytophaga broth). Flavobacterium columnare was isolated and detected in mucus 30 minutes following exposure by microbiological culture and PCR in all treatments except the negative controls. Gills were positive by culture and by PCR in all treatments at 30 minutes post treatment except the 10⁶ CFU/mL immersion treatment which did not yield positive culture and PCR results until 1 hour. Culture positive samples were observed in the internal organs (anterior and posterior kidney) and blood of the 10⁷⁸ CFU/mL treatments although at low numbers (≤10 CFU). Results of PCR paralleled that of culture for the mucus and gill samples when analyzing all treatments together over time suggesting either method is useful in determination of the presence ofF. columnare. Polymerase chain reaction was significantly (P < 0.001) better at detection ofF. columnare from skin/muscle than was the use of microbiological culture. These results suggest that PCR may be useful for rapid detection of F. columnare in the mucus.     

Growth performance,nutrient digestibility and digestive enzyme activity in Asian seabass,Lates calcarifer juveniles fed diets supplemented with cellulolytic and amylolytic gut bacteria isolated from brackishwater fish

Asian seabass, Lates calcarifer juveniles were fed for 30 days to evaluate the efficacy of cellulolytic (Bacillus sp. DDKRC1.) and amylolytic (Bacillus subtilis DDKRC5.) bacteria supplemented diets. Four experimental groups were maintained in triplicate of which group I was the control group and received no bacterial supplementation. Groups II, III and IV were fed diet supplemented with B. subtilis DDKRC5. (14.25 × 10⁷ CFU/mL), Bacillus sp. DDKRC1. (2.94 × 10⁷ CFU/mL) and mixture of both the microbes (1:1 ratio), respectively, @ 1% (v/w). After 30 days of feeding, fish reared as group IV showed significantly higher (P < 0.01) weight gain (141.42%), survival (91.50%), protein efficiency ratio (1.18) and significantly lower (P < 0.01) FCR (2.15) than that of other groups. Nutrient digestibility parameters were significantly (P < 0.01) higher in group IV followed by groups III, II and I. Digestive cellulase, amylase and protease activities in the gastrointestinal tract were also significantly (P < 0.01) higher in group IV. Amylolytic and cellulolytic microbial count in the gastrointestinal (GI) tract were significantly (P < 0.01) higher in groups II, III and IV as compared with that of control. It can be concluded that feed supplemented with mixture of B. subtilis DDKRC5. and Bacillus sp. DDKRC1. showed better performance in Asian seabass juveniles.     

Bacterial microflora associated with farmed freshwater prawn Macrobrachium rosenbergii (de Man) and the aquaculture environment

The initial counts of bacteria associated with farmed giant freshwater prawn (Macrobrachium rosenbergii de Man) as well as with the water and sediment from two farms located at Kottayam district in Kerala (India) were determined. A total of 367 randomly selected isolates were characterized and identified. Prawn samples yielded mean microbiological counts of 4.92 log CFU g^?1 of shell with muscle and 7.78 log CFU g^?1 of intestine at 30°C. Bacterial numbers in the intestine of prawn were much higher than those in the pond water. Motile and non‐motile aerobic Gram‐negative bacteria together with Enterobacteriaceae accounted for 60–70% of the mesophiles isolated from water and prawn. However, the microorganisms isolated in significant numbers from shell with muscle and intestine of prawn were not recovered from the growing waters. Among Gram‐positive bacteria, Micrococcus, Bacillus, coryneforms, and Arthrobacter were found. Faecal coliforms and enterococci were found in significant numbers in M. rosenbergii. The rearing practices such as feeding and pond fertilization could have influenced the microflora in prawn. The commensal microflora of freshwater prawn included opportunistic pathogens such as Aeromonas spp. and Streptococcus spp. Storage of prawn at elevated temperatures can permit their survival and growth leading to quality loss. Care should be exercised during handling and processing to prevent contamination of edible meat.     

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.     

Effects of potential probiotic Bacillus subtilis KADR1 and its subcellular components on immune responses and disease resistance in Labeo rohita

The present study was conducted to determine the effects of Bacillus subtilisKADR1 and its subcellular components on immunity and disease resistance in Labeo rohita against Aeromonas hydrophila infection. Fish were fed diet containing different concentrations of live bacterial cells (DI‐10⁶, DII‐10⁸ and DIII‐10¹⁰ CFU/g) and another group of fish were immunized intraperitoneally with cellular components (WCPs, CWPs and ECPs) of Bacillus subtilisKADR1. After 4 weeks of trial, fish were challenged intraperitoneally with Aeromonas hydrophila cell suspension and survival percentage was recorded. Significantly higher post‐challenge survivability was recorded in fish groups fed 10⁸ CFU/g of KADR1 (80.24%; RPS = 75.76%) or immunized with WCPs (77.77%; RPS = 72.73%), compared with the control (18.51%). Analysis of immunological parameters viz. serum lysozyme, phagocytosis, serum total protein, respiratory burst, serum IgM levels, superoxide dismutase and alternative complement pathway activity reflected significant enhancement (p < .05) of immune response in fish fed 10⁶, 10⁸ and 10¹⁰ CFU/g of live cells, or immunized with cellular components of Bacillus subtilisKADR1, with the highest values were observed DII fed group, followed by the group immunized with WCPs. Our results suggest that dietary administration of Bacillus subtilisKADR1 at 10⁸ CFU/g can effectively enhance the immune responses and disease resistance in Labeo rohita against Aeromonas hydrophila.     

Protective Effect of a Non-Bacteriocinogenic Lactococcus piscium CNCM I-4031 Strain Against Listeria monocytogenes in Sterilized Tropical Cooked Peeled Shrimp

The protective activity of a non-bacteriocinogenic Lactococcus piscium CNCM I-4031 strain against Listeria monocytogenes was investigated in tropical cooked peeled shrimp stored at 8°C in modified atmosphere packaging (50% N₂–50% CO₂). When inoculated alone (L. piscium 10⁷ CFU g^?1 and L. monocytogenes 10⁴ CFU g^?1), protective culture and target strain grew very well on shrimp reaching a maximum cell number of 10⁹ CFU g^?1 after 7 and 14 days, respectively. In the presence of L. piscium, growth of L. monocytogenes was totally prevented after 3 days of storage. The count was 3.4 log CFU g^?1 lower than in the control after 10 days and until the end of storage (31 days). Using the Seafood Spoilage and Safety Predictor Software (http://sssp.dtuaqua.dk), it was shown that pH decrease from 6.58 to 5.94 and lactic acid concentration of 89.65 mM measured in the co-inoculated batch did not fully explain the inhibition observed.     

粪肠球菌对吉富罗非鱼的生长、体组成、消化酶活性及血液生理生化指标的影响

为研究饲料中添加不同浓度的粪肠球菌对吉富罗非鱼生长、体组成、消化能力及血液生理生化指标的影响,实验选用初始体质量为(50.59±0.59)g的吉富罗非鱼300尾,随机分成5组,每组设3个重复,每个重复20尾鱼,养殖实验期60 d。分别投喂实测含1.3×10~2(对照组)、1.4×10~5、1.7×10~6、1.5×10~7和1.8×10~8 CFU/g粪肠球菌的5种等氮(36%)等脂(6.75%)的实验饲料。结果显示:(1)罗非鱼的末均重(FBW)、增重率(WGR)、特定生长率(SGR)和尾均摄食量(FI)均在1.5×10~7 CFU/g组达到最大且显著高于对照组,而饲料系数(FCR)显著低于对照组。以FBW、WGR和SGR为评价指标,通过二次回归分析得出,罗非鱼饲料的粪肠球菌适宜添加浓度范围为7.5×10~7~1.1×10~8 CFU/g。(2)各添加组的全鱼粗蛋白含量均显著高于对照组,1.5×10~7 CFU/g组的粗脂肪含量显著高于对照组,各组间全鱼水分和粗灰分含量无显著差异。1.5×10~7 CFU/g组的干物质、蛋白质和脂肪沉积率均达到最大值且显著高于对照组。(3)1.5×10~7和1.8×10~8 CFU/g组的肠脂肪酶活性均显著高于对照组,而1.8×10~8 CFU/g组的肠道蛋白酶活性显著低于对照组;各组间肠道淀粉酶活性无显著差异。(4)1.5×10~7 CFU/g组的平均红细胞体积、血红蛋白浓度和血小板数均显著低于对照组,各组间红细胞数无显著差异。(5)1.8×10~8 CFU/g组的血清中胆固醇、葡萄糖和丙二醛含量显著低于对照组;1.5×10~7 CFU/g组血清中碱性磷酸酶活性显著高于对照组,而谷丙转氨酶和谷草转氨酶活性显著低于对照组。综上所述,吉富罗非鱼(50~210 g)饲料中粪肠球菌的适宜添加浓度范围为7.5×10~7~1.1×10~8 CFU/g,但添加粪肠球菌对血液载氧能力有负面影响。