Showing papers on "Nile tilapia published in 2010"
TL;DR: The optimum growth of fry tilapia was obtained at 45% CP, while fingerling and advanced juvenile showed optimum growth performance with the 35%-CP diet, and Hematological variables were significantly affected by protein level, fish weight, and their interaction except for serum lipids which was not significant.
269 citations
TL;DR: It is shown that injecting germ cells directly into adult testis facilitates and enable fast generation of donor spermatogenesis and offspring compared to previously described methods, which indicates that a new suitable methodology for biotechnological investigations in aquaculture was established.
Abstract: Background Germ cell transplantation results in fertile recipients and is the only available approach to functionally investigate the spermatogonial stem cell biology in mammals and probably in other vertebrates. In the current study, we describe a novel non-surgical methodology for efficient spermatogonial transplantation into the testes of adult tilapia (O. niloticus), in which endogenous spermatogenesis had been depleted with the cytostatic drug busulfan. Methodology/Principal Findings Using two different tilapia strains, the production of fertile spermatozoa with donor characteristics was demonstrated in adult recipient, which also sired progeny with the donor genotype. Also, after cryopreservation tilapia spermatogonial cells were able to differentiate to spermatozoa in the testes of recipient fishes. These findings indicate that injecting germ cells directly into adult testis facilitates and enable fast generation of donor spermatogenesis and offspring compared to previously described methods. Conclusion Therefore, a new suitable methodology for biotechnological investigations in aquaculture was established, with a high potential to improve the production of commercially valuable fish, generate transgenic animals and preserve endangered fish species.
198 citations
TL;DR: Vitamin C at dose rate of 500 mg for one month could be a potential, less expensive, and promising dietary supplementation than inulin that would positively affect growth, hematology, innate immunity, and resistance of Nile tilapia (O. niloticus) in aquaculture.
176 citations
TL;DR: Results indicate that GT supplement is promising immunostimulant, which could improve fish performance, health, and prevent tilapia aermoniosis and the optimum GT level was 0.5 g/kg diet.
Abstract: The microbial diseases cause economic losses in aquaculture on global scale and the use of commercial antibiotics for disease treatment produces undesirable side effects. Because many medicinal herbs have evolved potent defense against pathogenic bacteria, there is a growing interest in these herbs as sources for natural antibacterial agents. In this context, green tea (GT), Camellia sinensis L., is considered as a promising source that may be used for improving the growth, survival, and protection of Nile tilapia, Oreochromis niloticus, against Aeromonas hydrophila infection. The present study was undertaken to evaluate the use of GT in practical fish diets and its impact on fish growth and health. GT leaves were ground and added to the ingredients of tested diets to represent 0.0 (control), 0.125, 0.25, 0.50, 1.0, or 2.0 g/kg diet. Fish (1.5‐2.0 g) were distributed to various treatments at a rate of 20 fish per 100-L aquarium and fed one of the experimental diets for 12 wk. After the feeding trial, fish of each treatment were challenged by pathogenic A. hydrophila, and they were kept under observation for 10 d during which abnormal clinical signs and the daily mortality was recorded. The growth-promoting influences of GT were observed and the optimum growth and feed utilization were obtained at 0.5 g GT/kg diet. The inclusion of GT in fish diet up to 0.5 g/kg diet enhanced the protein contents in fish body, while the lowest lipid contents were obtained at 0.0‐0.5 g GT/kg diet. Hematological and biochemical parameters were improved in fish fed 0.25‐2.0 g GT/kg diet, while the lowest values were obtained in the control. The survival of fish challenged with A. hydrophila increased with increasing GT level in fish diets. These results indicate that GT supplement is promising immunostimulant, which could improve fish performance, health, and prevent tilapia aermoniosis and the optimum GT level was 0.5 g/kg diet. Antibiotics have been generally used in fish diets to prevent and control any bacterial infection. The improper use of antibiotics can result in adverse effects in aquaculture organisms and the final consumer, as well as lead to
168 citations
TL;DR: It could be concluded that the whole yeast S. cerevisiae, beta-glucan and laminaran can be used as immunostimulants for the farmed Nile tilapia, under immune depressive stressful condition to increase their resistance to diseases.
164 citations
TL;DR: Results suggest that the peptide derived from Nile tilapia ( O. niloticus ) scale gelatin acts as a candidate against oxidative stress and could be used as a potential functional food ingredient.
162 citations
TL;DR: The analyzed strains from the three natural hosts did not show genetic relatedness, yet some of the bovine and human strains were able to infect fish and cause meningoencephalitis, suggesting that genetic linkage is not a prerequisite for S. agalactiae to cross the host-specific barrier.
126 citations
TL;DR: Results show that consequences of unintended releases of invasive higher order consumers can be important and predict that the proliferation of tilapia (and perhaps other aggressive aquaculture fishes) will have important detrimental effects on the structure of native food webs in shallow, structured coastal habitats.
Abstract: Recent studies have highlighted both the positive and negative impacts of species invasions. Most of these studies have been conducted on either immobile invasive plants or sessile fauna found at the base of food webs. Fewer studies have examined the impacts of vagile invasive consumers on native competitors. This is an issue of some importance given the controlling influence that consumers have on lower order plants and animals. Here, we present results of laboratory experiments designed to assess the impacts of unintended aquaculture releases of the Nile tilapia (Oreochromis niloticus), in estuaries of the Gulf of Mexico, on the functionally similar redspotted sunfish (Lepomis miniatus). Laboratory choice tests showed that tilapia prefer the same structured habitat that native sunfish prefer. In subsequent interspecific competition experiments, agonistic tilapia displaced sunfish from their preferred structured habitats. When a piscivore (largemouth bass) was present in the tank with both species, the survival of sunfish decreased. Based on these findings, if left unchecked, we predict that the proliferation of tilapia (and perhaps other aggressive aquaculture fishes) will have important detrimental effects on the structure of native food webs in shallow, structured coastal habitats. While it is likely that the impacts of higher trophic level invasive competitors will vary among species, these results show that consequences of unintended releases of invasive higher order consumers can be important.
114 citations
TL;DR: It could be concluded that echinacea and garlic improve the gain in body weight, survival rate and resistance against challenge infection, and both compounds showed extended effects after withdrawal and improved resistance to cold stress during the winter season.
Abstract: The study was conducted to evaluate the efficiency of echinacea (E) and garlic (G) supplemented diets as immunostimulant for tilapia (Oreochromis niloticus). Seven treatments were designed including a control (C). Fish were fed on 35% protein diet at a rate of 3% body weight per day. Echinacea (1.0 ppt) and garlic (3%) were incorporated in the feed, which was administered for periods of 1, 2 and 3 months (summer season), followed by basal diet for 4 more months (winter season). Neutrophil adherence and haematocrit values increased in both supplemented groups with prolonging period of application. The neutrophils adherence was significantly increased in all treatments except group administered echinacea for 1 month. The lymphocytic counts were significantly (p 85%) in all the supplemented groups. The percentage of protection, after challenge infection using pathogenic Aeromonas hydrophila was the highest in groups supplemented with echinacea and garlic for 3 months after summer and winter seasons. It could be concluded that echinacea and garlic improve the gain in body weight, survival rate and resistance against challenge infection. Both compounds showed extended effects after withdrawal and improved resistance to cold stress during the winter season. However, a full commercial cost benefit analysis is necessary before recommending their application in aquaculture.
107 citations
TL;DR: The mate allocation strategy has been successful in containing inbreeding and the effective population size is satisfactory for the sustainability of the selection program, hence the population would be unlikely to adapt and cope with severe environmental challenges.
95 citations
TL;DR: Evaluated stocking of non-native tilapia and carp species in fisheries enhancement in mainland SE Asia supported substantial increases in harvestable biomass while having only mild impacts on native fish communities, and encourages building on the results through a systematic and stakeholder-participatory evaluation.
TL;DR: It is indicated that PBM and PM can effectively replace FM in practical diets for fingerling Nile tilapia and survival and feed conversion ratio were not significantly influenced by replacement of FM with either PBM or PM.
Abstract: The apparent digestibility coefficients (ADC) of poultry by-product meal-pet food grade (PBM) and porcine meal (PM) were determined for fingerling male Nile tilapia. ADC for protein were 98.1% and 92.3% in PBM and PM, and 87.1% and 79.4% for energy. PBM and PM were then used as complete replacements for fish meal (FM) in practical diets for Nile tilapia formulated to contain equal digestible protein (300 g kg−1) and energy (16.74 MJ per 100 g) on an as-fed basis. Fingerlings (mean initial weight ±SD, 9.5 ± 0.015 g) were fed for 8 weeks on one of the four diets: FM-, PBM- or PM-based and a commercial feed. The ADC for protein in control and PBM diets (89.7% and 87.9%) were significantly higher than those for the control diet (81.96%). Growth performance and feed utilization were statistically similar between fish fed control and PBM diets, whereas the PM diet exhibited significantly lower performance compared with the control. However, the PM diet showed similar results to the commercial reference diet. Survival and feed conversion ratio were not significantly influenced by replacement of FM with either PBM or PM. The results indicated that PBM and PM can effectively replace FM in practical diets for fingerling Nile tilapia.
TL;DR: Sequencing the rRNA confirmed the morphological similarity between adults from the grey heron and the metacercarial stage from tilapia, and a level of genetic similarity with the other previously sequenced Clinostomum spp.
Abstract: The combined use of morphological and molecular studies allowed for the first time the recognition and description of the adult stage of Clinostomum cutaneum Paperna, 1964 from the grey heron Ardea cinerea L. in Kenya. A redescription of the metacercaria that infect Nile tilapia Oreochromis niloticus niloticus (L.) from the same aquatic environment is also presented. C. cutaneum differs from all other species of Clinostomum Leidy, 1856 in the shape of its uterus. Sequencing the rRNA confirmed the morphological similarity between adults from the grey heron and the metacercarial stage from tilapia, and a level of genetic similarity with the other previously sequenced Clinostomum spp. was observed. The need for a reorganisation of Clinostomum using both morphological and molecular methods is highlighted.
TL;DR: Experimental results indicate that short, sublethal, endosulfan exposure triggers a succession of events beginning with non-specific activation of macrophages followed by an exacerbated synthesis of the IL-2L factor by activated B cells which leads to significantly increased secretion of IgM and could in turn facilitate autoantibody production and the development of autoimmune pathologies.
TL;DR: In this article, the effect of carbohydrate sources for maintaining a high C:N ratio and tilapia driven bioturbation on pond ecology, production and economical performances in C/N controlled periphyton-based (C/N-CP) freshwater prawn ponds was investigated.
TL;DR: Of the four probiotic treatments, the 40% protein diet supplemented with yeast produced the best growth performance and feeding efficiency, suggesting that yeast is an appropriate growth-stimulating additive in tilapia cultivation.
Abstract: This study evaluated the effects of two types of probiotics, a mix of two bacteria and one yeast, on growth performance and intestinal enzyme activity in Nile tilapia. Three diets were formulated containing the optimum protein level (40%) for tilapia fry: one was supplemented at 0.1% with a bacterial mixture containingStreptococcus faecium and Lactobacillus acidophilus; a second was supplemented at 0.1% with the yeast Saccharomyces cerevisiae; and a third, was complemented with a control diet without supplements. Two additional diets were formulated to contain 27% protein to serve as a stress factor. They were supplemented at 0.1% with either the bacterial probiotic mix or the yeast. The diets were fed for 9 weeks to tilapia fry housed in 20-L tanks at two densities: a high density of 20 fry per tank as a stress factor; and a low density of 10 fry per tank. Every week an organism was selected from each tank for the enzymatic analyses of unicellular protein, alkaline phosphatase, disaccharidases and peptidase. Results indicate that the fry fed with diets containing probiotic supplement exhibited greater growth rate than those fed with control diet. Of the four probiotic treatments, the 40% protein diet supplemented with yeast produced the best growth performance and feeding efficiency. This was attributed to an increase in the alkaline phosphatase activity, suggesting that yeast is an appropriate growth-stimulating additive in tilapia cultivation.
Key words: Probiotic, Nile tilapia, enzymatic activity, streptococcus,Lactobacillus, Saccharomyces.
TL;DR: The responses of Mozambique and Nile tilapia acclimated to fresh water and brackish water were compared following acute salinity challenges and the difference in the SW adaptability of these species may be related to a limited capacity of Nile tilas to up-regulate NKCC gene expression, which is likely to be an essential component in the recruitment of SW-type chloride cells.
01 Jan 2010
TL;DR: The present results showed that all the diets containing different probiotic groups significantly improved Nile tilapia growth and feed utilization compared to the control diet, and recommend the incorporation of probiotics to Nile Tilapia feed as supplements to stimulate fish growth and digestion.
Abstract: A 60 days study was conducted to determine the effects of four probiotic groups,Bacillus subtilisNIOFSD017, LactobacillusplantarumNIOFSD018, a mixture containing bacterial isolates ( B. subtilisNIOFSD017 & L. plantarum NIOFSD018) and a yeast,Saccharomyces cerevisiaeNIOFSD019 ,isolated from healthy Nile tilapia, Oreochromis niloticuson growth performance, feed utilization and digestive enzymes activities of Nile tilapia. Five different experimental diets were formulated. The control diet had no probiotic supplement, diets (1 -3) were formulated to contain 10 7 CFU/g diet fromBacillus subtilisNIOFSD017 (D1), LactobacillusplantarumNIOFSD018 (D2), a mixture containing bacterial isolates (B. subtilisNIOFSD017 & L.plantarumNIOFSD018) (D3), while diet (D4) was formulated to contain 10 4 CFU/g diet ofa yeast,Saccharomyces cerevisiae NIOFSD019. The present results showed that all the diets containing different probiotic groups significantly (p<0.05) improved Nile tilapia growth and feed utilization compared to the control diet. These probiotics with the exception of S. cerevisiaeimprovedthe fish enzyme activities of amylase, protease and lipase in the gastrointestinal tract. S.cerevisiaeshowed a significantly higher amylase activity than the fish fed control diet; however the protease and lipase activities were not affected. The presen t results recommend the incorporation of probiotics to Nile tilapia feed as supplements to stimulate fish growth and digestion.
TL;DR: The illness observed in tilapia naturally infected with S. agalactiae was experimentally reproduced in this study, and the clinical signs produced were similar to those reported from the natural infections.
Abstract: The pathogenesis of a Streptococcus agalactiae was evaluated in a three-period experiment. Two groups of 40 fishes were intraperitoneally (i.p.) challenged in each experimental period with different infective doses of the pathogen. Doses varied from 1.0 x 106 to 1.5 x 108 CFU/fish. One group of 40 tilapia i.p. injected with tryptic soy broth (TSB) was used as a control group in each period. Mortalities varied from 67.5% in group 8 (infective dose 1.0 x 106 CFU/fish) to 90.0% in group 1 (infective dose 1.5 x 108 CFU/fish). Significant differences in mortalities were found only between group 8 and each of the other groups, except group 5 (infective dose 6.0 x 106 CFU/fish; mortality 75.0%). The highest mortality coefficients were observed in days 1-2 after inoculation (accumulated mortality 44.4%), and a second peak of mortality occurred at days 6-7. Challenged fishes from all the groups showed alterations in behaviour and similar clinical signs. These were anorexia, lethargy, erratic swimming, exophthalmia and ascites. Macroscopically, skin hemorrhage, splenomegaly, hepatomegaly with organ paleness and visceral adherences were observed. S. agalactiae was re-isolated from all the fishes from the experimental groups submitted to bacteriological examination. The illness observed in tilapia naturally infected with S. agalactiae was experimentally reproduced in this study, and the clinical signs produced were similar to those reported from the natural infections.
TL;DR: Different mucous cell and inflammatory cell responses show that glucan and LGG might have different immunostimulative effects, although they both reduced the intestinal damage following Aeromonas challenges.
Abstract: The present study histologically examined the effects of glucan-containing and Lactobacillus rhamnosus GG (LGG)-containing diets on intestinal damages inflicted on Nile tilapia by Aeromonas challenges. Tilapia were fed control, glucan, and LGG diets for 2 weeks and were subsequently challenged with Aeromonas. The intestines were then histologically examined at 1, 7, 14, and 21 days post-infection. Mortality following the challenge was lower for the fish fed the glucan and LGG diets. The intestines of these groups also showed increased inflammatory cell infiltration and reduced intestinal damage from Aeromonas. Moreover, inflammatory cell infiltration occurred more rapidly in the glucan-fed than in the LGG-fed fish following the challenge. Before the challenge, the dominant mucous cell was the acid type in all the tests. After the challenge, the main mucus cell type in the proximal intestine of the glucan-fed fish shifted to AB-PAS double-staining cells, while in the LGG-fed fish, it remained the acid type throughout the test period, and the number of double-staining cells was smaller than in the control fish after the challenge. Thus, the different mucous cell and inflammatory cell responses show that glucan and LGG might have different immunostimulative effects, although they both reduced the intestinal damage following Aeromonas challenges.
TL;DR: It is demonstrated that SPH is a promising protein feedstuff and could account for as much as 6% of Nile tilapia diets with no adverse effects on growth and nutrient utilization.
Abstract: A 45-day feeding trial was carried out to evaluate the use of shrimp protein hydrolysate (SPH) in diets for Oreochromis niloticus, L. SPH was included in isonitrogenous diets replacing fish meal protein by 0, 5, 10, and 20% and offered to Nile tilapia juveniles (1.7 ± 0.4 g) stocked in 40-L glass aquaria. The inclusion of SPH produced no significant differences (P ≥ 0.05) in final weight, survival, weight gain, average daily gain, specific growth rate, feed conversion ratio, protein efficiency ratio, or apparent net protein utilization. The inclusion of SPH Nile tilapia diets significantly affected (P < 0.05) the final fish body composition. Protein and ash contents decreased and fat content increased slightly with the increase in SPH. This study has demonstrated that SPH is a promising protein feedstuff and could account for as much as 6% of Nile tilapia diets with no adverse effects on growth and nutrient utilization.
TL;DR: This study details the first diagnosis of Francisella sp.
Abstract: This study details the first diagnosis of Francisella sp. in tilapia in the United Kingdom. Losses of tilapia fry at a recirculation fish farm in England were investigated, giving a presumptive positive diagnosis of infection with Francisella sp. by histopathological examination. Most fish sampled showed moderate to marked pathology of the major organs, with lesions being present in most tissues. The most obvious host response was granuloma formulation. A subsequent follow-up visit provided further evidence for the presence of a Francisella species. PCR amplicons were obtained using Francisella spp.-specific primers that shared 100% sequence identity with the 16S rRNA gene of the type strain of the species F. asiatica previously described as the cause of disease in tilapia in Southeast Asia and Central America. This outbreak and the subsequent investigation emphasise the importance of strict biosecurity at fish farms and the care that needs to be taken when using a new supplier of fish.
TL;DR: Fishmeal could be completely replaced by SPC without negative effect on growth by MHA supplementation and increasing feeding frequency, and results showed that complete replacement of fishmeal with SPC did not affect survival condition factor, visceralsomatic index of Nile tilapia.
Abstract: An 8 week growth trial was conducted to determine the effects of complete replacement of fishmeal protein by soy protein concentrate (SPC) on growth performance of Nile tilapia (Oreochromis niloticus GIFT strain) fry (initial body weight 1 6 0 0 g) In control diet, 135 g kg I fishmeal was used and in the other two diets 100% of fishmeal was replaced by SPC supplemented with or without methionine hydroxy analogue (MHA) according to the content in FM diet Fish of FM group were fed twice daily Fish of SPC6 group were fed SPC diet six times daily Fish of SPCM group were fed twice (SPCM2) or six times (SPCM6) daily The results showed that complete replacement of fishmeal with SPC did not affect survival condition factor, visceralsomatic index of Nile tilapia Feed intake (FI) and feed conversion ratio (FCR) of fish in SPCM2 and SPC6 groups were higher than those in FM and SPCM6 groups Specific growth rate (SGR) of fish in SPCM6 group was highest among four treatments Productive protein value (PPV) of SPCM2 and SPC6 groups were significantly lower than that of FM group Fishmeal could be completely replaced by SPC without negative effect on growth by MHA supplementation and increasing feeding frequency
TL;DR: The influence of fish on the reservoir plankton community and water transparency was significant and even greater than that of nutrient loading, and suggests that biomanipulation of filter-feeding tilapias may be of importance for water quality management of eutrophic reservoirs in tropical semi-arid regions.
Abstract: SUMMARY 1. The major aim of this study was to test the hypothesis that nutrient enrichment and the introduction of the Nile tilapia (Oreochromis niloticus), an exotic omnivorous filter-feeding fish, operate interdependently to regulate plankton communities and water transparency of a tropical reservoir in the semi-arid northeastern Brazil. 2. A field experiment was performed for 5 weeks in 20 enclosures (9.8 m 3 ) to which four treatments were randomly allocated: tilapia addition (F), nutrient addition (N), tilapia and nutrient addition (F + N) and a control treatment with no tilapia or nutrient addition (C). A two-way repeated measures ANOVA was undertaken to test for time, tilapia and nutrient effects and their interactions on water transparency, total phosphorus and total nitrogen concentrations, phytoplankton biovolume and zooplankton biomass. 3. Nutrient addition had no effect except on rotifer biomass, but there were significant fish effects on the biomass of total zooplankton, copepod nauplii, rotifers, cladocerans and calanoid copepods and on the biovolume of total phytoplankton, large algae (GALD ‡ 50 lm), Bacillariophyta and Zygnemaphyceae and on Secchi depth. In addition, we found significant interaction effects between tilapia and nutrients on Secchi depth and rotifers. Overall, tilapia decreased the biomass of most zooplankton taxa and large algae (diatoms) and decreased water transparency, while nutrient enrichment increased the biomass of rotifers, but only in the absence of tilapia. 4. In conclusion, the influence of fish on the reservoir plankton community and water transparency was significant and even greater than that of nutrient loading. This suggests that biomanipulation of filter-feeding tilapias may be of importance for water quality management of eutrophic reservoirs in tropical semi-arid regions.
TL;DR: In this article, the authors evaluated the resistance of Nile tilapia, Oreochromis niloticus (L), fed on organic selenium (OS)supplemented diet to water-born cadmium (Cd) toxicity.
Abstract: This study was carried out to evaluate the resistance of Nile tilapia, Oreochromis niloticus (L.), fed on organic selenium (OS)supplemented diet to water-born cadmium (Cd) toxicity. Fish (14.8±1.3 g) were randomly distributed at a density of 10 fish in 100-L aquarium. Fish in three treatments were fed a diet (30% crude protein) containing 0.5 g OS/kg diet (T1 - T3), while three other treatments (T4 - T6) were fed a basic diet without OS. During the feeding trial, fish in all groups were then exposed to 0.0, 1.116, or 2.232 mg Cd 2+ /L for 6 weeks. The fish performance and all the biochemical aspects were affected significantly by both Cd concentration, Se supplementation, and their interaction. OS supplementation enhanced fish growth, survival, and feed utilization, meanwhile the exposure to Cd reduced them (T1 vs T4, T2 vs T5, and T3 vs T6). All fish body constituents except moisture content were significantly affected by OS supplementation, Cd level, and their interaction. Crude protein and total lipids in fish body decreased, while ash content and Cd residue increased significantly with increasing Cd levels. OS reduced significantly Cd residues in fish body. Moreover, OS supplementation reduced creatinine, uric acid, AST, and ALT to below those of Cd-exposed treatments. Serum lipids increased, while protein decreased only in Cd-exposed groups (T5 and T6). Glutathione peroxidase (GPX) activity increased significantly with increasing Cd level and it was higher in T1 vs T4, T2 vs T5, and T3 vs T6. It could be concluded that OS supplementation may reduce the harmful effect of waterborn Cd in fish, which in turn improves the growth, survival, and feed efficiency.
TL;DR: The effects of fenitrothion were studied to determine the 96 h LC 50 value on Nile tilapia and investigate histopathological responses of fish exposed to sublethal fenItrothion concentrations, which showed histopathic alterations in the gills, liver, kidney, brain and testes.
TL;DR: The enzymatic activity of lactate dehydrogenise (LDH) increased in hypoxia group, while a significant reduction appeared in overcrowding and starved fish compared to control group, and the pyruvate kinase (PK) activity decreased in hypoxic group but increased in other group.
TL;DR: In eutrophic tropical lakes, fish seem to have a high tolerance to the toxicity of cyanotoxins including MCs, but there is a possibility of accumulating these toxins in their tissue with the threat of transferring them higher up in the food chain.
Abstract: Catches of the economically important Nile tilapia (Oreochromis niloticus L.) from two eutrophic tropical lakes in Uganda, Lake Mburo and Murchison Bay, Lake Victoria, were examined to determine the presence of microcystins (MCs) in gut, liver and muscle of the fish. Analysis for MCs (RR, LR and YR) in both fish and water samples was by liquid chromatography coupled with mass spectroscopy (LC-MS) method. Physico-chemical parameters were also measured to establish the status of both lakes. MC-RR was the most prominent MC detected in Lake Mburo and Murchison Bay samples, there was no evidence of significant seasonal variation in the concentration of MCs in fish tissue. MCs were detected in all water samples from both study lakes. The mean concentration of MCs in water was found higher in dry times for Lake Mburo (P < 0.05) and higher in wet times for Murchison Bay (P < 0.05). MC concentrations in the fish guts were positively related with MC concentrations in water samples from Murchison bay (P < 0.05), no such correlation was found in Lake Mburo. In eutrophic tropical lakes, fish seem to have a high tolerance to the toxicity of cyanotoxins including MCs. However, there is a possibility of accumulating these toxins in their tissue with the threat of transferring them higher up in the food chain. Due to a low sample size and short sampling period, the results can only serve to highlight the potential risk of MC accumulation in Nile tilapia in these lakes. Further studies are needed for the purpose of risk assessment.
TL;DR: Tilapia self-feed at night (although locomotor activity was mostly diurnal) and chose plant-diets containing phytase, which should be taken into account when designing feeding strategies and practical diets for tilapia aquaculture.
Abstract: Fish do not feed at any time of the day and on whatever food item they encounter in the wild, but they show daily rhythms of feeding activity and dietary selection. The aim of this research was to investigate the daily rhythms of behavior in Nile tilapia self-fed with plant-based diets supplemented with different levels of exogenous phytase (an enzyme that hydrolyzes non-digestible phytate and improves the nutritional value of the diet). To this end, ten males were individually kept in 50-L tanks, each equipped with two self-feeders and one infrared photo-cell connected to a computer. The selection factors investigated were the level of phytase supplementation (0 IU kg − 1 vs 1500 IU kg − 1 ; 1500 IU kg − 1 vs 4000 IU kg − 1 ) or sodium phytate (1% phytate vs 1% phytate + 1500 IU kg − 1 phytase). The results revealed that 66.7% of total daily activity occurred during the day, while feeding was strictly nocturnal, with 93.0% of the daily food demands occurring at night. Tilapia preferred the diet with 1500 IU kg − 1 phytase rather than the control or 4000 IU kg − 1 diets. When exogenous sodium phytate was added to the diet, tilapia preferred the phytase diet. In conclusion tilapia self-feed at night (although locomotor activity was mostly diurnal) and chose plant-diets containing phytase, which should be taken into account when designing feeding strategies and practical diets for tilapia aquaculture.
TL;DR: The results suggest that the developed S. iniae vaccine has broad ranging protection among isolates exhibiting different protein profiles, and shared immunogenic proteins among all isolates in the molecular mass range of 22-35 kDa and high molecular mass material >150 kDa.
Abstract: Streptococcus iniae is a significant pathogen impacting aquaculture production worldwide. The objectives of this study were to determine whether a developed modified S. iniae (ARS-98-60) bacterin vaccine is efficacious in Nile tilapia, Oreochromis niloticus (L.), against challenge with heterologous isolates from diverse geographical locations and to evaluate protein and antigenic variability among the isolates tested. Two groups of tilapia (approximately 5 g) were intraperitoneally (IP) vaccinated with 100 microL of the vaccine or sham vaccinated with 100 microL of sterile tryptic soy broth and held for 28 days. Fish were challenged with each isolate by IP injection of 2-3 x 10(7) CFU per fish using calcein to mark fish prior to cohabitation for challenge. The results demonstrated significant protection against all challenge isolates, and relative percent survivals ranged from 79% to 100%. SDS-PAGE analysis of whole-cell lysate proteins from the S. iniae isolates demonstrated similar protein profiles between 10 and 31 kDa and variation in profiles between 35 and 100 kDa. Western blot analysis using antiserum from vaccinated fish (ARS-98-60) demonstrated shared immunogenic proteins among all isolates in the molecular mass range of 22-35 kDa and high molecular mass material >150 kDa. The results suggest that the developed S. iniae vaccine has broad ranging protection among isolates exhibiting different protein profiles.