Hybrid Tilapia Research Articles

Potential of mealworms used in polyhydroxyalkanoate/bioplastic recovery as red hybrid tilapia (Oreochromis sp.) feed ingredient

Polyhydroxyalkanoates (PHAs) are bio-based polymers produced in bacterial cells to replace some petrochemical plastics. It has always been a challenge to commercialise PHA due in part to the costly recovery processes of the PHA granules from the bacterial cells. The biological approach of using mealworms, Tenebrio molitor, for the recovery of PHA from the bacterial cells is a newly established method that is at the scale-up stage. On the other hand, the aquaculture feed industry needs a low-cost mealworm meal as a protein source. We aimed at studying the nutritional value of the mealworms (which are by-products) used for the poly(3-hydroxybutyrate) (PHB) (the most common type of PHA) recovery from the bacterial and examining the effect of the mealworms on the growth performance, and feed utilization efficiency of red hybrid tilapia (Oreochromis sp.). The cells were fed to the mealworms to digest the proteinaceous cellular materials and excrete the PHB granules in the form of fecal pellets. The resulting mealworms were used as fishmeal replacement to formulate five isonitrogenous (35% crude protein) and isolipidic (8% lipid) diets at mealworm meal (MwM) inclusion levels of 0% (MwM0/control diet), 25% (MwM25), 50% (MwM50), 75% (MwM75) or 100% (MwM100). The results showed good nutritive value mealworms [high protein (75%), low-lipid (10%)] and up to 75% MwM inclusion diet was good in supplying satisfactory nutrients and energy to the red hybrid tilapia. This approach is beneficial in a way that minimal cost was involved in recovering kilograms of PHB and the proteins, lipids, and minerals from the bacterial cells do not end up as wastes but in turn, are used as nutrition by the larvae.

Whole-Genome Sequence of Streptococcus iniae Strain AH1, Isolated from Hybrid Tilapia (Oreochromis niloticus × Oreochromis aureus).

ABSTRACTHere, we describe the whole-genome sequence of Streptococcus iniae strain AH1, which was isolated from moribund farmed hybrid tilapia (Oreochromis niloticus × Oreochromis aureus) in Saudi Arabia. The genome is composed of a single linear chromosome of 2,068,661 bp, with a G+C content of 36.8%.

The Immunostimulant Effects of Isochrysis galbana Supplemented Diet on the Spleen of Red Hybrid Tilapia (Oreochromis spp.) Evaluated by Nuclear Magnetic Resonance Metabolomics

Significant measures at improving aquaculture health have to be taken since disease outbreaks commonly occur in the fast-growing aquaculture industry. This study aimed to determine the immunomodulatory properties of an indigenous Malaysian microalgae species, Isochrysis galbana (IG), on red hybrid tilapia (Oreochromis spp.). Then, the potential biomarkers for immunomodulatory properties were identified through metabolic changes in the spleen using the proton nuclear magnetic resonance (1H NMR) metabolomics approach. IG was cultivated in an indoor annular photobioreactor before being harvested and freeze-dried into dried biomass. The dried IG biomass was incorporated into four experimental diets in concentrations of 0% (diet A), 0.6% (diet B), 1.3% (diet C), 2.5% (diet D), and 5.0% (diet E) basal feed per kg. After 14 days of feeding, diet D has consistently improved the immune responses of innate immunity such as phagocytosis (P>0.05), respiratory burst (P<0.05), and lymphoproliferation (P<0.05) activities which might have helped in maintaining the overall health status of red hybrid tilapia. The orthogonal partial least squares (OPLS) model between diets D and A indicated three important metabolites, namely, isoleucine, glutamate, and tyrosine, have significantly been upregulated when compared to the control. Meanwhile, IG supplementation also resulted in lower concentrations of various metabolites in the spleen including α/β-glucose, choline, hypoxanthine, adenosine, and inosine. Hence, the application of metabolomics tools has proved the potential of IG-incorporated fish diet by strongly influencing the metabolic condition in red hybrid tilapia spleen cells and further boosting the immune response and health status in improving aquaculture health.

Effect of papaya (Carica papaya) leaf extract as dietary growth promoter supplement in red hybrid tilapia (Oreochromis mossambicus × Oreochromis niloticus) diet

The purpose of this experiment was to examine the potential use of Carica papaya leaf extract as a supplement to promote growth and improve feed utilization in red hybrid tilapia. Five diets were formulated containing isolipidic (80 g/kg) and isonitrogenic (350 g/kg) levels. All feeds contained similar types and amounts of raw materials but differed in the inclusion of papaya leaf extract (0, 5, 10, 20 and 40 g/kg feed). The initial size of fish used was 2.3 ± 0.01 g. Each diet was performed in triplicate tanks, and the feeding period was 12 weeks. Fish fed diet containing 2% papaya leaf extract (PLE) had the highest final weight, 31.14 ± 1.47 g, followed by 1% PLE (27.27 ± 1.75 g). These two diets (1% and 2%) were also showed significant improvements of weight gain, SGR, and feed efficiency of the red hybrid tilapia (p < 0.05). However, papaya leaf extract did not affect the HSI, VSI, PER, digestive enzymes activity, blood composition, and survival rate. Supplementing the diets with papaya leaf extract lowered serum urea. Findings of this research suggest that adding papaya leaf extract to the diet of red hybrid tilapia improves growth and feed efficiency without adversely affecting blood parameters. Therefore, an inclusion level between 1% and 2% of the papaya leaf extract is recommended as a feed additive to promote red hybrid tilapia fry growth.

Integration of mRNA and miRNA Profiling Reveals Heterosis in Oreochromis niloticus × O. aureus Hybrid Tilapia.

Simple SummaryHybrid tilapia (Oreochromis niloticus ♀ × O. aureus ♂) are commercially important in China. Because cultured hybrids have superior growth and survival rate relative to the parental stocks, parent species potentially represent model taxa to analyze the molecular mechanisms of hybrid vigor. Comparisons of the growth and hematologic biochemical characters and transcriptional analyses of mRNA and miRNA, approximately 21-nt-long noncoding RNAs that negatively regulate gene expression at the post transcriptional level, were performed in hybrid and parental tilapia stocks to investigate the underlying molecular basis for heterosis. The present study indicated that dominance and overdominance models are widespread in transcriptional and post-transcriptional regulation of genes involved in growth, metabolism, immunity, and antioxidant capacity in hybrid tilapia, thus providing new insights into molecular heterosis in hybrid tilapia and advancing our understanding of the complex mechanisms involved in this phenomenon in aquatic animals.Heterosis is a widespread biological phenomenon in fishes, in which hybrids have superior traits to parents. However, the underlying molecular basis for heterosis remains uncertain. Heterosis in growth and survival rates is apparent in hybrid tilapia (Oreochromis niloticus ♀ × O. aureus ♂). Comparisons of growth and hematological biochemical characteristics and mRNA and miRNA transcriptional analyses were performed in hybrid and parents tilapia stocks to investigate the underlying molecular basis for heterosis. Growth characteristics and hematological glucose and cholesterol parameters were significantly improved in hybrids. Of 3097 differentially expressed genes (DEGs) and 120 differentially expressed miRNAs (DEMs) identified among three stocks (O. niloticus, O. aureus, and hybrids), 1598 DEGs and 62 DEMs were non-additively expressed in hybrids. Both expression level dominance and overdominance patterns occurred for DEGs and DEMs, indicating that dominance and overdominance models are widespread in the transcriptional and post-transcriptional regulation of genes involved in growth, metabolism, immunity, and antioxidant capacity in hybrid tilapia. Moreover, potential negative regulation networks between DEMs and predicted target DEGs revealed that most DEGs from miRNA-mRNA pairs are up-regulated. Dominance and overdominance models in levels of transcriptome and miRNAome facilitate the integration of advantageous parental alleles into hybrids, contributing to heterosis of growth and improved survival. The present study provides new insights into molecular heterosis in hybrid tilapia, advancing our understanding of the complex mechanisms involved in this phenomenon in aquatic animals.

Morphological description and molecular characterization of Contracaecum larvae (Nematoda: Anisakidae) parasitizing market-size hybrid tilapia (Oreochromis aureus x Oreochromis niloticus) and red drum (Sciaenops ocellatus) farmed in Israel

Nematodes belonging to the genus Contracaecum (family: Anisakidae) are heteroxenous parasites with a complex life cycle. Contracaecum larvae infecting farmed fish and fishery products are economically important causing market rejection in massive infection and may have zoonotic potential. In Israel, Contracaecum larvae have been described morphologically in several fish species; however, none of these descriptions were supported by molecular tools. In 2019–2020, hybrid tilapia (Oreochromis aureus x Oreochromis niloticus) and red drum (Sciaenops ocellatus), farmed in polyculture were found to be heavily infected with nematodes referable to Contracaecum larvae. Prevalence of infection in hybrid tilapia and red drum was 53.8% and 40.9%, respectively. A combined (morphological and molecular) approach revealed that both infected fish species were parasitized by the same species of Contracaecum, although larvae in hybrid tilapia were localized in the pericardial cavity whereas in red drum, they were observed in the abdominal cavity. Genetic analysis of internal transcribed spacer rDNA and cox2 mtDNA showed high similarity to unidentified Contracaecum larvae detected in several fish species in Ethiopia, Egypt and Kenya. In this study, molecular and morphological analyses place the possible new species in the C. multipapillatum complex and was provisionally named C. multipapillatum E. Further analyses combining morphological and molecular approaches are required on adult specimens collected from piscivorous birds living in the same area to support the identification of a potentially new species.

Transcriptome Profiling Revealed Basis for Growth Heterosis in Hybrid Tilapia (Oreochromis niloticus ♀ × O. aureus ♂)

Hybrid tilapia were produced from hybridization of Nile tilapia (Oreochromis niloticus) and blue tilapia (O. aureus). Comparative transcriptome analysis was carried out on the liver of hybrid tilapia and their parents by RNA sequencing. A total of 2319 differentially expressed genes (DEGs) were identified. Trend co-expression analysis showed that non-additive gene expression accounted for 67.1% of all DEGs. Gene Ontology and KEGG enrichment analyses classified the respective DEGs. Gene functional enrichment analysis indicated that most up-regulated genes, such as FASN, ACSL1, ACSL3, ACSL6, ACACA, ELOVL6, G6PD, ENO1, GATM, and ME3, were involved in metabolism, including fatty acid biosynthesis, unsaturated fatty acid biosynthesis, glycolysis, pentose phosphate pathway, amino acid metabolism, pyruvate metabolism, and the tricarboxylic acid cycle. The expression levels of a gene related to ribosomal biosynthesis in eukaryotes, GSH-Px, and those associated with heat shock proteins (HSPs), such as HSPA5 and HSP70, were significantly down-regulated compared with the parent tilapia lineages. The results revealed that the metabolic pathway in hybrid tilapia was up-regulated, with significantly improved fatty acid metabolism and carbon metabolism, whereas ribosome biosynthesis in eukaryotes and basal defense response were significantly down-regulated. These findings provide new insights into our understanding of growth heterosis in hybrid tilapia.

Prevalence and Antimicrobial Resistance of Escherichia coli, Salmonella and Vibrio Derived from Farm-Raised Red Hybrid Tilapia (Oreochromis spp.) and Asian Sea Bass (Lates calcarifer, Bloch 1970) on the West Coast of Peninsular Malaysia.

Antibiotics are widely used in intensive fish farming, which in turn increases the emergence of antimicrobial-resistant (AMR) bacteria in the aquatic environment. The current study investigates the prevalence and determines the antimicrobial susceptibility of E. coli, Salmonella, and Vibrio in farmed fishes on the west coast of Peninsular Malaysia. Over a period of 12 months, 32 aquaculture farms from the Malaysian states of Selangor, Negeri Sembilan, Melaka, and Perak were sampled. Both E. coli and Salmonella were highly resistant to erythromycin, ampicillin, tetracycline, and trimethoprim, while Vibrio was highly resistant to ampicillin and streptomycin. Resistance to the antibiotics listed as the highest priority and critically important for human therapy, such as colistin in E. coli (18.1%) and Salmonella (20%) in fish, is a growing public health concern. The multi-drug resistance (MDR) levels of E. coli and Salmonella in tilapia were 46.5% and 77.8%, respectively. Meanwhile, the MDR levels of E. coli, Salmonella, V. parahaemolyticus, V. vulnificus and V. cholerae in Asian seabass were 34%, 100%, 21.6%, 8.3% and 16.7%, respectively. Our findings provide much-needed information on AMR in aquaculture settings that can be used to tailor better strategies for the use of antibiotics in aquaculture production at the local and regional levels.

Sacha inchi meal as a fish-meal replacer in red hybrid tilapia (Oreochromis niloticus × O. mossambicus) feeds: effects on dietary digestibility, growth metrics, hematology, and liver and intestinal histology

Sacha inchi meal as a fish-meal replacer in red hybrid tilapia (Oreochromis niloticus × O. mossambicus) feeds: effects on dietary digestibility, growth metrics, hematology, and liver and intestinal histology

Dual infections of tilapia parvovirus (TiPV) and tilapia lake virus (TiLV) in multiple tilapia farms: Their impacts, genetic diversity, viral tropism, and pathological effects

Tilapia culture is an essential protein-rich food production sector worldwide. The emergence of pathogens is sometimes associated with fatal outbreaks in tilapia, which dramatically slow production and result in severe economic losses. While tilapia lake virus (TiLV) infection has been associated with fatal diseases in tilapia, the novel tilapia parvovirus (TiPV) has been recently identified and reported to be associated with mass mortality events in tilapia farming. In this study, we identified the coinfection of a novel TiPV and TiLV in multiple independent tilapia farms in Thailand, thus causing significant losses. The full-length genomes of the TiPV were characterized, and a phylogenetic analysis was performed, indicating the genetic diversity of the TiPV and multiple amino acid mutations found in the structural protein VP1. Using the in situ hybridization (ISH) technique, TiPV was localized in the gills, heart, brain, liver, pancreas, spleen, intestine, kidney, eyes, and muscles of tilapia, with evidence of cellular tropism. The TiLV localization was confirmed using a dual ISH/immunohistochemistry protocol and transmission electron microscopy, which indicated a potential association with pathological alterations. Both TiPV and TiLV were successfully propagated in tilapia brain cells and the fish cell line E-11. This study also provided an indication of the potential cellular roles of the pathological features of TiPV coinfection with TiLV in red hybrid tilapia. Since mutations in the parvovirus structural protein led to virulence and extensive infection in susceptible hosts, several point mutations in the VP1 gene with amino acid signatures of TiPV found in tilapia in Thailand warrant future observations. Although the synergism between TiPV and TiLV coinfection remains undetermined, the contributory role of these two viruses requires intensive focus. Further investigations should lead to a suitable strategy for disease control.

Effect of Supplementation of Dried Bioflocs Produced by Freeze-Drying and Oven-Drying Methods on Water Quality, Growth Performance and Proximate Composition of Red Hybrid Tilapia

Supplementation of dried bioflocs for red hybrid tilapia (Oreochromis sp.) was examined during 57 days of feeding trials. Five experimental treatments; T1 (the control; without bioflocs), T2 (4% freeze-dried bioflocs), T3 (16% freeze-dried bioflocs), T4 (4% oven-dried bioflocs), and T5 (16% oven-dried bioflocs) were prepared to examine the water quality, growth performance and body composition of red hybrid tilapia. T2 and T4 treatments resulted in a higher growth rate and survival similar to the control, while T3 and T5 treatments showed the lowest values of growth performance among all treatments. T1 treatment showed the best quality of culture water followed by T2 and T4 treatments, while T3 treatment resulted in poor water quality followed by T5 treatment. Based on these results, the ratios of bioflocs (4% and 16%) had more effect on fish growth and water quality than the drying methods (freeze-drying and oven-drying). The ratio of 4% freeze-dried or oven-dried bioflocs provided higher growth rates and better water quality parameters similar to the control, while the ratio of 16% showed the worst growth performance and water quality in the present study. In addition, body compositions of tilapia fed 4% dried bioflocs showed better nutritional value than tilapia fed 16% dried bioflocs. Protein and energy levels showed an increasing trend with decreasing supplement levels of bioflocs. Moisture content was significantly higher when supplementation of 16% bioflocs was used. Overall, supplementation of 4% freeze-dried or oven-dried bioflocs can be successively included in red hybrid tilapia diets without any effects on growth or body composition and can result in a good quality of culture water for red hybrid tilapia.

Solar-powered aquaponics prototype as sustainable approach for food production

This paper presents the establishment of a solar-powered aquaponics prototype as a sustainable, cost effective and environmentally sound approach for food production. In this study, a prototype bench top aquaponics rig with an integrated 20 W solar panel were fabricated for the cultivation of red Hybrid Tilapia (Oreochromis spp.) and leaf mustard (Brassica juncea). The size of the fish tank is about 29.5L and serves as the base for the setup. Additionally, the hydroponic grower compartment (0.45 m (L) × 0.32 m (W) × 0.13 m (H)) was stacked on top of the fish tank and was filled with LECA media bed for the plant growth. Two important operating parameters were studied. First, the amount of energy produced by the solar panel and the energy consumption by the water pump used in the setup. Secondly, the resultant effects from fish cultivation and plants growth on the water qualities and nitrification efficiency of the aquaponics unit. The aquaponics unit was operated for a month and the values of pH, temperature, and ammonia level were measured to be within the range of 6.4–7.2, 27.1–31.7 °C, and 1 mg·L−1, respectively. Survival rate for fish was about 75% with specific growth rate (SGR) of 3.75% per day and food conversion ratio of about 1.15. A slight nutrient deficiency was evident and plants showed a healthy growth with height gain as high as 5 cm was achieved. Despite raining season, our data shows that the energy produced via 20 W solar panel enabled the unit to run at night without depending on local electricity for nearly two hours. Clearly, a larger solar panel is needed for longer operation. Nevertheless, the study has proven the potential of operating a low cost aquaponics setup using renewable energy for a sustainable food production method.

Feed additive for fishdiet with antioxidant and immunostimulating effect

The increase in the production of aquaculture products confirms the relevance of the development of feed production in order to provide the industry with high-quality compound feeds and feed additives that meet modern requirements and biological needs of cultivated fish. Therefore, the development of aquaculture requires special attention to the feeding process and the use of full-fledged and environmentally safe feeds for all types of aquacultures. Antioxidants of natural origin are increasingly used in feed production. In the course of the work, the positive properties of antioxidant complexes containing the bioflavonoid dihydroquercetin in combination with vitamin E were studied when enriching the diet of a tilapia hybrid (Oreochromis mossambicus × Oreochromis niloticus). As a result of the research, it was found that the inclusion of dihydroquercetin in the composition of production feeds significantly improved productivity indicators and the main criteria for the formation of muscle mass in fish. The use of bioflavonoid dihydroquercetin allowed to increase productivity by 30.0%. The positive effect of the feed additive on morphological and biochemical parameters of blood was noted, which indicates an increase in natural resistance. The study of feed quality indicators confirmed the inhibition of oxidation processes in feed with the addition of dihydroquercetin. During the period of storage of feed in the experimental batch of feed, the level of peroxide number decreased by 3 times, and the acid number decreased by 28.4%. Taking into account the positive properties of bioflavonoid, it is recommended to further study the effectiveness of this biologically active additive in order to introduce it more widely into the practice of feed production.

DNA Damage in Hybrid Tilapia (Oreochromis niloticus x O. aureus) Exposed to Short-Transport Process

In this study, DNA damage in hybrid tilapia exposed to the short-transport process has been investigated. Gill samples were taken from tilapia which after immediately from the transport process (t0 group), after 6 hours from transport process (t6 group), after 12 hours from transport process (t12 group), after 24 hours from transport process (t24 group) and not applied transport process (control group) have been investigated and the results have been compared as statistically. The Damage frequency (%), Arbitrary Unit and Genetic Damage Index (%) were evaluated in gill cells of tilapia. As a result of the study, it is determined that highest the damage frequencies (%) as 69.00±4.58 and 66.00±3.00 were significantly observed in t0 and t6 groups respectively (P

Effects of Probiotics on Growth, Survival, Water Quality and Disease Resistance of Red Hybrid Tilapia (Oreochromis spp.) Fingerlings in a Biofloc System.

Simple SummaryStreptococcosis, a warm-water pathogenic bacteria, has greatly affected red hybrid tilapia production in Malaysia over the years, causing mass mortality in various culture systems. Probiotics have been used to treat and prevent bacterial diseases, including streptococcosis, yet they require constant application to ensure that their concentration is adequate. Incorporating probiotics in a biofloc system may reduce this issue as the effective microorganism may further flourish and be utilized by the fish. The objectives of this study were to evaluate the influence of probiotic addition on the growth performance and water quality of red hybrid tilapia. From the study, it was observed that a probiotic mix was able to inhibit Streptococcus spp., improve red hybrid tilapia performance and disease resistance against streptococcosis. Providing a beneficial mix of probiotics can effectively improve biofloc culture in red hybrid tilapia culture.Biofloc technology has shown positive effects in aquaculture, especially on the growth performance of cultured animals. The aims of this study were to evaluate the effects of adding different probiotic strains in a biofloc system on the growth performance and disease resistance of red hybrid tilapia (Oreochromis spp.). Three different probiotics (Lysinibacillus fusiformis SPS11, Bacillus amyloliquefaciens L9, and Enterococcus hirae LAB3), commercial probiotics (MG1) and a mixed probiotics (MP) combining all three strains were used in this study. The in vitro assay results showed that the mixed probiotic (MP) was able to inhibit the growth of Streptococcus agalactiae and Streptococcus iniae significantly compared to the single and commercial probiotic. The efficacy of MP was further tested in in vivo tilapia culture challenged with S. agalactiae. The best specific growth rate (3.73 ± 0.23% day−1) and feed conversion ratio (0.76 ± 0.04) were recorded in the group of biofloc with addition of MP. After being challenged with S. agalactiae, the group of biofloc with MP had significantly higher survival (83 ± 1.43%) compared to the other groups. Furthermore, the nitrogen concentration (NO2-N and NH4-N) was significantly lower in all the biofloc groups compared to the control. Hence, the addition of probiotics was able to provide beneficial effects to red hybrid tilapia culture in the biofloc system.

Comparative Study of Intestinal Microbiota Composition of Six Edible Fish Species.

Intensive freshwater aquaculture in the Spring Valley, Israel, is implemented mainly in earthen fishponds and reservoirs that are stocked with a variety of edible fish species. Here we sampled six different healthy fish species from these intensive aquacultures. The fish were hybrid striped bass, European bass, red drum (all carnivores), hybrid tilapia, flathead grey mullet (both herbivores), and common carp (an omnivore). Significant differences were found among the intestinal microbiota of the six studied fish species. The microbiota composition diversity was strongly related to the trophic level of the fish, such that there was a significant difference between the carnivore and the herbivore species, while the omnivore species was not significantly different from either group. The most abundant genus in the majority of the fishes’ intestinal microbiota was Cetobacterium. Furthermore, we found that beside Cetobacterium, a unique combination of taxa with relative abundance >10% characterized the intestine microbiota of each fish species: unclassified Mycoplasmataceae, Aeromonas, and Vibrio (hybrid striped bass); Turicibacter and Clostridiaceae 1 (European bass); Vibrio (red drum); ZOR0006—Firmicutes (hybrid tilapia); unclassified Mycoplasmataceae and unclassified Vibrionaceae (flathead grey mullet); and Aeromonas (common carp). We conclude that each fish species has a specific bacterial genera combination that characterizes it. Moreover, diet and the trophic level of the fish have a major influence on the gut microbiota of healthy fish that grow in intensive freshwater aquaculture.

Development and application of TaqMan probe-based quantitative PCR assays for the detection of tilapia parvovirus.

Tilapia parvovirus (TiPV) is a novel parvovirus associated with high mortality in Nile tilapia and red hybrid tilapia, leading to severe economic losses for tilapia aquaculture. It is critical to develop a sensitive and accurate assay to detect TiPV in fish tissues. In this study, new TaqMan probe-based quantitative PCR (qPCR) assays targeting the non-structural (NS) and viral protein (VP) genes of TiPV were developed. The standard curves of the assays were 95.64%-98.96% over a wide linear range of 109 -101 copies of the corresponding standard DNA per reaction. The intra- and inter-assay coefficients of variation were in the ranges 0.54%-2.50% and 0.13%-1.17%, respectively, which suggests good repeatability and reproducibility. The detection limit of the TaqMan TiPV assays was 10 copies/µl. The application of the TaqMan qPCR assays to field samples revealed that they had comparable sensitivity to a previously developed SYBR Green qPCR, but more sensitive than the conventional PCR. No cross-reactivity of the TaqMan TiPV assays was found with the samples infected with other viruses and bacteria. Overall, the assays offered high sensitivity and specificity in the detection of low concentrations of TiPV DNA in infected tilapia samples. These new TaqMan qPCR assays could provide a valuable diagnostic tool for the reliable and specific detection of TiPV in experimental and field samples.

Growth and yield of tilapia hybrid (red tilapia) in aquaponics system

An aquaponics system was studied through the integrated culture of tilapia hybrid (Red Tilapia) and lettuce var. Estrosa in a recirculating system for 100 days. Red Tilapia with an Average Body Weight (ABW) of 36.99g were stocked in two treatments, 80 fish/m3 (Treatment I) and 100 fish/m3 (Treatment II), to assess the fish growth, survival, yield and production of lettuce. Specific Growth Rate (SGR) in Treatment I was 1.03 and Treatment II, 1.14. Feed Conversion Ratio (FCR) varies from 1.83 to 1.90, associated with stocking density. Treatment II incurred the highest survival rate of 92.85% while Treatment I has 90.19%. Biomass production of red tilapia was significantly higher in Treatment I with 1,761.00 g than in Treatment II with 1,341.00 g (p = 0.012). Highest yield of lettuce was obtained during the second cropping with 250.00g for Treatment I and 202.00g for Treatment II, but no significant difference was observed between the two treatments. Correlation analysis showed no significant relationship between red tilapia weights and water quality parameters such as ammonia, nitrite, nitrate, temperature, pH, Total Dissolved Solids, and DO. However, a significant positive relationship was revealed between the biomass of lettuce and nitrite during the first cropping in Treatment II. This study demonstrated the stocking density of 80 fish/m3 had better effect on the growth, FCR, and biomass production of red tilapia under an aquaponics system.

Comparative Pathogenicity of Aeromonas spp. in Cultured Red Hybrid Tilapia (Oreochromis niloticus × O. mossambicus).

Simple SummaryRecently, there has been an emergence of a hypervirulent pathotype of Aeromonas hydrophila, vAh strain. The strain was responsible for the acute mass mortalities among catfish in the USA. One of the unique abilities of the vAh strain is to utilize myo-inositol as a sole carbon source and this ability has been linked to contribute to its virulence. Therefore, the present study was carried out to screen and assess the virulence of myo-inositol-utilizing strains among Aeromonas spp. in Malaysia. Out of the 124 Aeromonas isolates screened, only A. dhakensis strain 1P11S3 was able to utilize myo-inositol as a sole carbon source. The only myo-inositol-utilizing strain was compared with five non-myo-inositol-utilizing Aeromonas spp. in an experimental challenge test using red hybrid tilapia (Oreochromis mossambicus × O. niloticus). Our findings demonstrated that the most virulent strains were A. dhakensis strain 4PS2 and A. hydrophila strain 8TK3, followed by A. dhakensis strain 1P11S3 (the only myo-inositol-utilizing strain), A. veronii strain 6TS5, A. caviae strain 7X11 and the least virulent strain was A. jandaei strain 7KL3 under current disease model. Therefore, more data are needed to assess the influence of myo-inositol utilizing ability on the pathogenesis of Aeromonas spp.The genus Aeromonas has been recognised as an important pathogenic species in aquaculture that causes motile Aeromonas septicaemia (MAS) or less severe, chronic infections. This study compares the pathogenicity of the different Aeromonas spp. that were previously isolated from freshwater fish with signs of MAS. A total of 124 isolates of Aeromonas spp. were initially screened for the ability to grow on M9 agar with myo-inositol as a sole carbon source, which is a discriminatory phenotype for the hypervirulent A. hydrophila (vAh) pathotype. Subsequently, LD50 of six selected Aeromonas spp. were determined by intraperitoneal injection of bacterial suspension containing 103, 105, and 107 CFU/mL of the respective Aeromonas sp. to red hybrid tilapias. The kidneys, livers and spleens of infected moribund fish were examined for histopathological changes. The screening revealed that only A. dhakensis 1P11S3 was able to grow using myo-inositol as a sole carbon source, and no vAh strains were identified. The LD50–240h of A. dhakensis 1P11S3 was 107 CFU/mL, while the non-myo-inositol utilizing A. dhakensis 4PS2 and A. hydrophila 8TK3 was lower at 105 CFU/mL. Similarly, tilapia challenged with the myo-inositol A. dhakensis 1P11S3 showed significantly (p < 0.05) less severe signs, gross and histopathological lesions, and a lower mortality rate than the non-myo-inositol A. dhakensis 4PS2 and A. hydrophila 8TK3. These findings suggested that myo-inositol utilizing A. dhakensis 1P11S3 was not a hypervirulent Aeromonas sp. under current experimental disease challenge conditions, and that diverse Aeromonas spp. are of concern in aquaculture farmed freshwater fish. Therefore, future study is warranted on genomic level to further elucidate the influence of myo-inositol utilizing ability on the pathogenesis of Aeromonas spp., since this ability correlates with hypervirulence in A. hydrophila strains.

Pathological Changes Associated with Aeromonas hydrophila Dose-Dependent Infection and Heat Stress in Red Hybrid Tilapia

Pathological Changes Associated with Aeromonas hydrophila Dose-Dependent Infection and Heat Stress in Red Hybrid Tilapia