Oreochromis Spp Research Articles

Erratum: Characterization of a Pathogenic <em>Escherichia coli</em> Strain Derived from <em>Oreochromis</em> spp. Farms Using Whole-Genome Sequencing

An erratum was issued for:Characterization of a Pathogenic Escherichia coli Strain Derived from Oreochromis spp. Farms Using Whole-Genome Sequencing. The Authors section was updated from: José Antonio Magaña-Lizárraga1, Bruno Gómez-Gil2, Julissa Enciso-Ibarra2, María Elena Báez-Flores1 1Unidad de Investigaciones en Salud Pública "Dra. Kaethe Willms", Facultad de Ciencias Químico Biológicas, Universidad Autónoma de Sinaloa, Ciudad Universitaria 2Centro de Investigación en Alimentación y Desarrollo, A. C. (CIAD), Unidad Mazatlán en Acuicultura y Manejo Ambiental to: José Antonio Magaña-Lizárraga1, Bruno Gómez-Gil2, Julissa Enciso-Ibarra2, María Elena Báez-Flores1 1Unidad de Investigaciones en Salud Pública "Dra. Kaethe Willms", Facultad de Ciencias Químico Biológicas, Universidad Autónoma de Sinaloa 2Centro de Investigación en Alimentación y Desarrollo, A. C. (CIAD), Unidad Mazatlán en Acuicultura y Manejo Ambiental.

Effects of Chromium-L-Methionine in Combination with a Zinc Amino Acid Complex or Selenomethionine on Growth Performance, Intestinal Morphology, and Antioxidative Enzymes in Red Tilapia Oreochromis spp.

Simple SummaryThe purpose of this study was to develop diet optimization for the growth and health of fish under intensive aquaculture systems, with a focus on the farming of Nile tilapia and red tilapia in Thailand. Diets and proper nutrition are more important than ever in raising healthy, antibiotic-free fish. Organic trace minerals have been used to promote the growth and health status of fish in aquafeeds. In this investigation, we studied the effects of chromium-L-methionine, in combination with a zinc amino acid complexor in combination with selenomethionine, on the growth performance, feed utilization, and immune responses of red tilapia. The results for the combination of chromium-L-methionine with a zinc amino acid complex showed beneficial effects for red tilapia in terms of growth performance, feed utilization, and intestinal morphology. The results for the combination of chromium-L-methionine with selenomethionine demonstrated that the levels of antioxidative enzymes, especially glutathione, could be increased to provide an innate immune response in red tilapia.To consider diet optimization for the growth and health of fish under intensive aquaculture systems, with a focus on the farming of Nile tilapia and red tilapia in Thailand, we conducted an experiment based on a completely randomized design (CRD), with three treatments and four replicates. Three diets, supplemented with different trace minerals, were applied to selected groups of fish: (a) a control diet, without organic trace minerals supplementation; (b) a T1 diet of chromium-L-methionine at 500 ppb, in combination with a zinc amino acid complex at 60 parts per million (ppm); and (c) a T2 diet of chromium-L-methionine at 500 ppb in combination with selenomethionine at 300 ppb. Red tilapia with an initial mean weight of 190 ± 12 g/fish were randomly distributed into cages of 2 × 2 × 2.5 m in a freshwater pond (12 cages in total), with 34 fish per cage and a density of 17 fish/m3. During the 8 week feeding trial, the fish were fed 3–4% of their body weight twice a day. The fish were weighed, then blood samples were collected to study their immune responses. The intestines were collected, measured, and analyzed at the end of the feeding trial. The results showed that the red tilapia that were fed with diets of chromium-L-methionine in combination with a zinc amino acid complex in the T1 treatment had significantly (p < 0.05) higher final weights, weight gains, average daily gains (ADGs), and better feed conversion ratios (FCRs), compared with fish that were fed with the control diet without organic trace minerals and with fish that were fed with the T2 diet (p < 0.05). The midgut and hindgut villus heights of the group fed with chromium-L-methionine in combination with a zinc amino acid complex in the T1 treatment were significantly higher than those of the other groups (p < 0.05). The levels of the antioxidative enzyme superoxide dismutase (SOD) and lysozyme activity were not significantly different from those of fish that were fed with the control diet (p > 0.05), whereas the glutathione level tended to increase (p < 0.1) in fish that were fed with chromium-L-methionine in combination with selenomethionine in the T2 treatment. Therefore, we concluded that chromium-L-methionine in combination with a zinc amino acid complex or selenomethionine clearly enhanced red tilapia’s growth performance and feed utilization through the promotion of antioxidative enzyme activity and immune response.

Quality of fresh frozen tilapia from selected supermarkets in Malawi

Fish provides a major source of dietary animal protein to Malawi’s population. Majority of tilapia in supermarkets are of different origins and bought from different suppliers. Fish is highly perishable commodity and its quality degrades even in frozen form due to microbial activity. The quality of frozen tilapia (the most commonly traded and consumed fish in Malawi) sold in some reputable supermarkets in Malawi was determined. Fish were collected from nine (9) reputable supermarkets in three (3) regions of the country (north, central and south) and analysed in the laboratory for sensory quality, microbiological, chemical and proximate analyses. Sensory quality evaluation was performed following guidelines earlier developed for fresh tilapia (Oreochromis spp.) in Malawi. Differences and changes in the fish sensory quality were attributed to the effect of storage duration and conditions within the freezer compartment. Two types of bacteria namely, Salmonella spp. and Escherichia coli were identified on the frozen tilapia, suggesting poor and unhygienic pre-handling. Despite the presence of bacteria on the fish and differences in sensory quality, the frozen tilapia were within the acceptable range for human consumption. Nutrient composition of frozen tilapia was high despite differences (p&lt;0.05) in moisture, ash and crude fat. Fish from different origin were sold mixed in all supermarkets, poor handling along the fish market chain was identified as the major source of fish contamination. Mechanical damages were reminiscent of the effects of frozen storage. There is a need to establish optimum storage time for frozen tilapia in supermarkets to provide products with good quality in terms of sensory properties, nutrient content and safe microbial loads. Key words: fish quality, fresh fish, frozen fish, tilapia, supermarkets, Malawi, Oreochromis spp.

Inclusion of cocoa shell flour (Theobroma cacao L) in the diet of (Oreochromis spp)

The research was carried out at the Socio Tilapia fish farm facilities; via Quevedo, Santo Domingo, Los Ríos province, at an altitude of 100 meters above sea level, to determine the inclusion of cocoa shell flour in the fish farming process (Theobroma cacao L) as an alternative protein source in intensive tilapia farming (Oreochromis spp). The sample size consisted of 128 fish, with 8 experimental units per cage, fed for 42 days, with the inclusion of cocoa shell meal levels (0, 4, 8, and 12%), in four treatments and four replicates, with commercial pelleted concentrate as control; an experimental design (DCA) was used, with multiple comparison measures according to Tukey's test (P &lt; 0.05). The results in all variables had a better performance in the T3 treatment (12% cocoa shell meal), without affecting any parameter, obtaining better results for feed conversion (1.45%), weight gain (24.05%), feed consumption (675.06 g) and total length with an average of (1 cm) corresponding to the days of investigation of the 32 experimental units. It was established that in fillet yield and carcass yield there is a usable value, 47.49 %, and 95.42 %, while a lower value in the by-products, 54.65 %, respectively.

Widespread presence of a highly virulent Edwardsiella ictaluri strain in farmed tilapia, Oreochromis spp.

Edwardsiella ictaluri is an emerging bacterial pathogen that affects farmed tilapia (Oreochromis spp.). This study reports the widespread presence of E. ictaluri in farmed tilapia in Vietnam. Among 26 disease outbreaks from nine provinces in Northern Vietnam during 2019-2021, 19 outbreaks originated from imported seeds, while outbreaks in seven farms were from domestic sources. Clinically sick fish showed the appearance of numerous white spots in visceral organs, and accumulative mortality reached 30%-65%. A total of 26 representative bacterial isolates recovered from 26 disease outbreaks were identified as E. ictaluri based on a combination of phenotypic tests, genus- and species-specific polymerase chain reaction assays, 16S rRNA and gyrB sequencing, and phylogenetic analysis. All isolates harboured the same virulence gene profiles esrC+ , evpC+ , ureA-C+ , eseI- , escD- and virD4- . Antimicrobial susceptibility tests revealed that 80.8%-100% of isolates were multidrug resistant, with resistance to 4-8 antimicrobials in the groups of penicillin, macrolides, sulfonamides, amphenicols and glycopeptides. The experimental challenge successfully induced disease that mimicked natural infection. The median lethal doses (LD50 ) of the tested isolates (n = 4) were 42-61 colony forming units/fish, indicating their extremely high virulence. This emerging pathogen is established and has spread to various geographical locations, causing serious impacts on farmed tilapia in northern Vietnam. It is likely that this pathogen will continue to spread through contaminated stocks (both imported and domestic sources) and persist. Thus, increased awareness, combined with biosecurity measures and emergent vaccination programs is essential to mitigate the negative impact of this emerging disease on the tilapia farming industry.

First identification of two co-existing genome-wide significant sex quantitative trait loci (QTL) in red tilapia using integrative QTL mapping.

Red tilapia (Oreochromis spp.) is one of the most popular fish in China due to its bright red appearance, fast growth rate, and strong adaptability. Understanding the sex determination mechanisms is of vital importance for the selection of all-male lines to increase aquacultural production of red tilapia. In this research, the genetic architecture for sex from four mapping populations (n=1 090) of red tilapia was analyzed by quantitative trait loci (QTL)-seq, linkage-based QTL mapping, and linkage disequilibrium (LD)-based genome-wide association studies. Two genome-wide significant QTL intervals associated with sex were identified on ChrLG1 (22.4–23.9 Mb) and ChrLG23 (32.0–35.9 Mb), respectively. The QTL on ChrLG1 was detected in family 1 (FAM1), FAM2, and FAM4, and the other QTL on ChrLG23 was detected in FAM3 and FAM4. Four microsatellite markers located within the QTL were successfully developed for marker-assisted selection. Interestingly, three (lpp, sox14, and amh) of the 12 candidate genes located near or on the two QTL intervals were abundantly expressed in males, while the remaining genes were more highly expressed in females. Seven genes (scly, ube3a, lpp, gpr17, oca2, cog4, and atp10a) were significantly differentially expressed between the male and female groups. Furthermore, LD block analysis suggested that a cluster of genes on ChrLG23 may participate in regulating sex development in red tilapia. Our study provides important information on the genetic architecture of sex in red tilapia and should facilitate further exploration of sex determination mechanisms in this species.

Comparison between kuruma shrimp, Marsupenaeus japonicus, Bate (1888) cultured in monoculture system and polyculture system with red tilapia Oreochromis spp fingerlings

Post larvae of Kuruma shrimp, Marsupenaeus japonicus (PL25) were stocked at 10shrimp/m2 (MC) in nine concrete ponds (4.0mx6.0mx1.25m, total area 24.0m2) filled up with seawater at a salinity of 38ppt. Kuruma shrimp were stocked with Red tilapia Oreochromis spp fingerlings (4.0g±0.5) collected from the marine hatchery of MRC. Red tilapia were stocked at 0.25g (PC1) and 0.5g (PC2) fingerlings/m2 in the polyculture treatment ponds with shrimp larvae. Results showed significantly differences (P&lt;0.5) in body weight of M.japonicus cultured in MC system in comparison with PC1 and PC2 systems. The best food conversion ratio FCR (wait/gain) was for those shrimp cultured in MC. No significantly differences were observed in PER and PEP between shrimp cultured in the three evaluated systems. The juveniles cultured in MC system had significantly (P&gt;0.05) higher survival values than juveniles cultured in PC1 and PC2. Final BW, weight gain WG and weekly growth rate WGR of Juveniles cultured in PC1 system were higher than Juveniles cultured in PC2 system. Survival rate of red tilapia cultured in PC system was 100% in both PC1 and PC2 systems.

Effect of Different Feed Restrictions on Growth, Biometric, and Hematological Response of Juvenile Red Tilapia (Oreochromis spp)

Highlight ResearchThere has been a significant decrease in growth, condition factors, hepatosomatic index along viscerosomatic index with the length of time for feed restriction, although fasting for up to 28 days did not cause fish mortalityHematological parameters such as RBCs, WBCs, hematocrit, and hemoglobin decreased significantly, but after re-feeding increased significantly in consecutive timesThe blood glucose levels decreased during feed restriction and gradually increased after re-feedingFeed restriction fish gained weight continuously during re-feeding, but no displaying compensatory growthThe decrease in hematological parameters did not indicate stress levels in fish, but reflected a lack of nutrition condition AbstractThe management of red tilapia culture can be improved through restriction of feed. This study aimed to determine the impact of feed restriction time and re-feeding on the growth and hematological performance of juvenile red tilapia. This study used an experimental method with a completely randomized design consisting of five treatments with four replications, namely the fish were given food for 28 days (A), 7 days of feed restriction followed by 21 days of refeeding (B), 14 days of feed restriction followed by 14 days of refeeding (C), 21 days of feed restriction followed by 7 days of refeeding (D) and 28 days of feed restriction (E). The parameters observed were growth, biometry, and hematological values. The results showed that during the feed restriction period there was a significant decrease in growth, condition factors, hepatosomatic index along with viscerosomatic index with the length of time for feed restriction, although fasting for up to 28 days did not cause fish mortality. Hematological parameters such as RBCs, WBCs, hematocrit, and hemoglobin decreased significantly, but after re-feeding, they increased significantly in consecutive times. As for the blood glucose levels decreased during feed restriction and gradually increased after re-feeding. This study stated that feed restriction fish gained weight continuously during re-feeding, but no displaying compensatory growth. The results suggested that the decrease in hematological parameters did not indicate stress levels in fish, but reflected a lack of nutrition condition.

Effects of triclosan on sperm mobility in Oreochromis spp

Effects of triclosan on sperm mobility in Oreochromis spp

Nile Tilapia: A Model for Studying Teleost Color Patterns.

The diverse color patterns of cichlid fishes play an important role in mate choice and speciation. Here we develop the Nile tilapia (Oreochromis niloticus) as a model system for studying the developmental genetics of cichlid color patterns. We identified 4 types of pigment cells: melanophores, xanthophores, iridophores and erythrophores, and characterized their first appearance in wild-type fish. We mutated 25 genes involved in melanogenesis, pteridine metabolism, and the carotenoid absorption and cleavage pathways. Among the 25 mutated genes, 13 genes had a phenotype in both the F0 and F2 generations. None of F1 heterozygotes had phenotype. By comparing the color pattern of our mutants with that of red tilapia (Oreochromis spp), a natural mutant produced during hybridization of tilapia species, we found that the pigmentation of the body and eye is controlled by different genes. Previously studied genes like mitf, kita/kitlga, pmel, tyrb, hps4, gch2, csf1ra, pax7b, and bco2b were proved to be of great significance for color patterning in tilapia. Our results suggested that tilapia, a fish with 4 types of pigment cells and a vertically barred wild-type color pattern, together with various natural and artificially induced color gene mutants, can serve as an excellent model system for study color patterning in vertebrates.

Gestión de agronegocios de la tilapia roja (Oreochromis Spp. O) y su comercialización

The production of Red Tilapia (Oreochromis spp. O) has maintained an outstanding participation worldwide, with production exceeding one million tons. In Ecuador the Red Tilapia is the second crop with the highest economic participation, where the province of Guayas and El Oro are the most developed have the activity. The present study has the objective of evaluating the agribusiness management of the Red Tilapia and its commercialization in the Puerto Jelí parish, belonging to the Santa Rosa canton of the El Oro province, Ecuador. A deductive and analytical research method was used, obtaining information through a questionnaire addressed to the residents. A cross-sectional descriptive methodological design was used with categorical and quantitative variables. The results revealed that Tilapia is the second type of fish with the highest consumption in Puerto Jelí, whose consumption frequency is once a week, while the price that they are available to pay is from $ 1.50 to $ 2, 50, and the main characteristic when buying that people consider is freshness. This denotes that the commercialization of Tilapia is a viable agribusiness alternative that generates profitability, contributing to economic stability.

Improving genetic quality of cultivated aquatic species under a breeding program: Case study of first generation (G1) population of red tilapia (Oreochromis spp)

A body weight based selection protocol is the most common practice in the genetic improvement programs for aquaculture species. It might be one of the criteria to be considered in the aquatic resources management scheme. This experiment aimed to evaluate the genetic enhancement of selected first-generation (G1) of red tilapia. Fish were bred under fullsib mating design at hapa of 2×2 m2. The communal growing out of fingerlings was carried out in an earthen pond for 120 days. The stocking density of fingerlings was 7 fish per m2. Fish were fed with commercial floating fish feed at a rate of 5-10% of biomass twice a day. The results showed that the population of males and females of red tilapia in the first generation (G1) grew faster than the previous generation (G0). The selection response values were 19.52 % and 12.05 % for male and female populations, respectively. The heritability values in male and female red tilapia populations were in the medium category with a value of 0.33 and 0.25, respectively. The results showed that the breeding program increased the genetic quality of fish in terms of body weight based growth in the first generation of red tilapia.

Protein Profiling of Oreochromis spp. Epidermal Mucus Subsequent to Challenge of Common Freshwater Bacteria

Protein Profiling of Oreochromis spp. Epidermal Mucus Subsequent to Challenge of Common Freshwater Bacteria

In Vitro Antibacterial Potential of Salix babylonica Extract against Bacteria that Affect Oncorhynchus mykiss and Oreochromis spp.

Simple SummaryAquaculture development is limited by several diseases associated with bacteria that have developed resistance to antibiotics. In this context, new treatment alternatives are necessary. The aim of the present study was to evaluate the in vitro antibacterial effects of Salix babylonica hydro-alcoholic extract against some bacteria that affect rainbow trout (Oncorhynchus mykiss) and tilapia (Oreochromis spp.). The results indicate that Salix babylonica hydro-alcoholic extract has an antibacterial effect and could be an alternative treatment in diseases caused by microorganisms resistant to drugs in aquaculture.Aquaculture development is limited by bacteria associated with several diseases; antibiotics are used for the treatment of these affections, but bacteria have developed resistance to these drugs. It is important to develop effective treatments that allow the production of antibiotic-free food. The aim of the present study is to evaluate the in vitro antibacterial effects of Salix babylonica hydro-alcoholic extract (SbHE) against Aeromonas hydrophila, Listonella anguillarum, Edwarsiella tarda, and Streptococcus iniae, bacteria that affect Oncorhynchus mykiss and Oreochromis spp. production. SbHE was obtained through the maceration technique. Reference strains were used and their sensitivity to antibiotics was determined. Minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of SbHE were determined. Results showed that three of four evaluated bacteria were multidrug resistant, except S. iniae. SbHE showed antibacterial activity against all bacteria. Results indicate an MIC of 1.56 to 25 mg/mL and an MBC of 3.12 to 100 mg/mL. The greatest inhibitory activity occurred against L. anguillarum obtaining a MIC of 1.56 mg/mL and an MBC of 3.12 mg/mL. Results indicate that SbHE has bactericidal activity against A. hydrophila, L. anguilalurm, and S. iniae as well as bacteriostatic activity against E. tarda and could be an alternative treatment against these bacteria.

Acute toxicity of 4 algal toxins on 5 common fishes of the pearl river estuary

This study studied the common economic fish in the Pearl River Estuary, including Konosirus punctatus, Hypophthalmichthys nobilis, Oreochromis spp, dace and Carassius auratus. We evaluated the toxic effects using hydrostatic toxicity. The method is to expose the test organism to different concentrations of algal toxin, and obtain the LC50 by using the probability unit method. The results showed that the same algal toxin had significant differences in toxicity to five species of fish. 96h-LC50 of Anabaena-a toxins on 5 common fishes. is 38.1μg/L, 45.6μg/L, 68.2μg/L, 78.2 μg/L, 64.5 μg/L; MC-LR is 66.9μg/L, 226.8μg/L, 255.4μg/L, 317.5 μg/L, 184.3 μg/L; MC-RR is 91.2μg/L, 266μg/L, 285μg/L, 337.6 μg/L, 214.8 μg/L; MC-YR is 95μg/L, 299μg/L, 505μg/L, 709μg/L, 439 μg/L. Anabaena-a toxins is the most toxic to the test organism, while MC-YR is the weakest. The toxicity of different algal toxins is different for the tested organisms. In this study, we found that the toxicity of the four algal toxins was from strong to weak: Anabaena-a toxins>MC-LR>MC-RR>MC-YR, this research results can provide reference and basic data support for the water environment quality and water supply safety in Dawan District and Pearl River Estuary.

Levels and risk assessment of polycyclic aromatic hydrocarbons in water and fish of Rivers Niger and Benue confluence Lokoja, Nigeria.

As from last decade, the pollution of water bodies by chemical toxicants has become a topic of public discourse and concern in many countries. Polycyclic aromatic hydrocarbons (PAHs) are carcinogens and being ubiquitous in nature, are daily being released into water bodies as a result of anthropogenic sources. The water samples were collected with plastic bottles/containers by dipping the sampler below the water surface to minimize the contamination of water sample by surface films and cocked below water surface to avoid air entrapment while the fish samples namely Clarias spp (Catfish) and Oreochromis spp (Tilapias) were purchased from fishermen at the bank of the river confluence. Three water samples each were collected from five sample points [A], [B], [C], [D] and [E] created for that purpose at each visit monthly for a period of six months and taken in an ice-cooler box to the laboratory. In all a total of 90 water samples and 20 fish samples were analysed. The water samples were preserved in a refrigerator below 4°C prior to analysis. The concentrations of the sixteen US EPA priority polycyclic aromatic hydrocarbons (PAHs) were investigated using Gas chromatography coupled with Mass Spectrometer detector (GC-MS) after liquid-liquid and solid-liquid extractions. The concentrations of the six detected PAHs in water were of the following ranges: Nap(Not Detected {ND} to 0.543), Ph(ND to 0.083) Ant (ND to 0.083), BbF(0.080 to 0.093), BkF(0,083 to 0.093) and BaP(0.083 to 0.113) mg/L with distribution pattern of Nap>BaP > BbF=BkF > Ant = Ph. The mean concentration value of PAHs in Catfish and Tilapia were Nap(2.383 and 1.947), Ph(0.050 and 0.057), Ant(0.057 and 0.057), BbF(0.043 and ND), BkF(0.043 and ND) and BaP(0.050 and ND). The health risk assessment showed that the concentration of Benzo[a]pyrene, a known indicator of the presence of carcinogenic PAHs is of health risk concern. The PAHs were not significantly different in the water and fish respectively and the correlation studies showed that the PAHs were from the same source. The study showed clearly that the levels of PAHs in the samples are of concern due to increasing pollution.

Identifying a Long QTL Cluster Across chrLG18 Associated with Salt Tolerance in Tilapia Using GWAS and QTL-seq

Understanding the genetic mechanism of osmoregulation is important for the improvement of salt tolerance in tilapia. In our previous study, we have identified a major quantitative trait locus (QTL) region located at 23.0Mb of chrLG18 in a Nile tilapia line by QTL-seq. However, the conservation of these QTLs in other tilapia populations or species is not clear. In this study, we successfully investigated the QTLs associated with salt tolerance in a mass cross population from the GIFT line of Nile tilapia (Oreochromis niloticus) using a ddRAD-seq-based genome-wide association study (GWAS) and in a full-sib family from the Malaysia red tilapia strain (Oreochromis spp) using QTL-seq. Our study confirmed the major QTL interval that is located at nearly 23.0Mb of chrLG18 in Nile tilapia and revealed a long QTL cluster across chrLG18 controlling for the salt-tolerant trait in both red tilapia and Nile tilapia. This is the first GWAS analysis on salt tolerance in tilapia. Our finding provides important insights into the genetic architecture of salinity tolerance in tilapia and supplies a basis for fine mapping QTLs, marker-assisted selection, and further detailed functional analysis of the underlying genes for salt tolerance in tilapia.

Heritability estimates and selection response for resistance to Streptococcus agalactiae in red tilapia Oreochromis spp.

This study presents results of selection response to Streptococcosis agalactiae (SA) resistance in a commercial stock of red tilapia (Oreochromis spp.) after one generation of selection. Families were produced from 93 males and 128 females using a nested design (1 male: 2 females). At 60 days post-hatch, 30 fish from each family were challenged by intraperitoneal injection of bacterial solution (SA strain AQSA01) at the 96 h LD50 concentration (1 × 109 CFU mL−1) and observed for 14 days. Disease-resistance was measured as a binary trait (dead/alive) and as survival time, or the number of days from challenge initiation until death. Animal and sire-dam models were applied with body weight fitted as a covariate, whereas tank and generation were treated as fixed effects. Data from 128 full-sib and 35 half-sib families was used to estimate variance components using ASREML version 4.1. Heritability estimates for the base generation (G0) were highest, 0.25 ± 0.12 for binary data on the liability scale and 0.20 ± 0.08 for days until death. Breeding candidates in G0, selected from the top 10 high-ranking families based on their estimated breeding values (EBVs), were used to produce 25 full- and six half-sib families. When data from G0 and G1 were combined, heritability estimates were 0.29 ± 0.11 and 0.27 ± 0.08 for threshold sire-dam and animal models, respectively. The realized genetic gain was 2.53 days for survival time, equivalent to about a 58% improvement from 4.3 days in the base generation. In terms of binary response, the probability that the G1 fish survived to the end of challenge period increased 10% from the base generation. This study demonstrates a significant selection potential for increased disease-resistance to S. agalactiae in red tilapia.

A comparative study on the external parasites of Oreochromis spp from wild and cultured setting in Behera, Egypt

A total one hundred (Tilapia spp) Oreochromis spp fishes were collected and examined for the presence of ectoparasites, fifty fishes from each farm and wild environment (River Nile) over a period of five months from February to July 2017. Total infestation rate of ectoparasites from cultured Oreochromis spp (100%) was higher than of those recorded in wild Oreochromis spp (74 %). The ciliated protozoan parasite Trichodina spp was the most abundant ectoparasite recovered from both cultured and wild environment. However, the study revealed two kinds of external parasites, protozoa and monogenetic trematodes. Protozoans showed the most prevalent ectoparasites (100%) in cultured Oreochromis spp and (74%) in wild Orechromis spp, while the monogenetic trematodes recorded (20%) in cultured fishes only while wild fishes showed no infestation. Furthermore, the load of protozoans in cultured Oreochromis differed significantly (P 0.05). As well as monogenetic trematodes recovered from cultured fishes were differing significantly (P< 0.001) from those recovered from wild fishes but this difference was applied only on Dactylogyrus spp since the Gyrodactlus spp did not show any significant.

Valoración económica del uso de ensilaje de residuos piscícolas en la alimentación de oreochromis spp

Feeding in fish farming systems accounts for between 50% and 70% of production costs, with fishmeal being the most widely used animal protein source; therefore, lower-cost protein alternatives should be sought to improve profitability. The objective was to economically evaluate the use of chemical silage of trout viscera (CSTV) in the diet of red tilapia ( Oreochromis spp ), in four balanced diets so: T1 (control) and with inclusion of CSTV, T2 (10%), T3 (20%) and T4 (30%), supplied to 128 juveniles of red Tilapia with an average weight of 142,14 ± 4,74 g. The conversion rates and economic profitability rates were evaluated, as well as partial budget analysis. There were significant differences (P<0,05) for the economic conversion index, economic profitability index, net profit, net profit increase and the marginal rate of return according to the level of inclusion of CSTV. It was evidenced that to include 20% of silage in the diet, it obtains greater economic retribution associated to the cost of the feeding per kilogram of meat of fish produced.