Showing papers on "Nile tilapia published in 2000"
TL;DR: These experiments strongly implicate aromatase activity as a key factor in sexual differentiation in the Nile tilapia.
Abstract: A series of experiments was carried out in which genetically female Nile tilapia (Oreochromis niloticus) fry were treated with Fadrozole, a nonsteroidal aromatase inhibitor (AI), in the diet during the period of sexual differentiation. Batches of tilapia fry treated with AI during the first 30 days following yolk-sac resorption (7–37 days post hatch, dph) showed a dose-dependent increase in the percentage of males from 0 to 200 mg · kg–1. The percentage of males remained approximately constant (92.5–96.0%) from 200 to 500 mg · kg–1. Any continuous 2- or 3-week treatment with 500 mg · kg–1 AI in this 4-week period successfully masculinized the majority of the treated fish (>80%). Treatments of 1 week duration revealed that the most sensitive time to AI lies in the first week (between 7 and 14 dph). Progeny testing of males from AI-treated groups gave results indicating that these were XX males, as expected. These experiments strongly implicate aromatase activity as a key factor in sexual differentiation in the Nile tilapia. J. Exp. Zool. 287:46–53, 2000. © 2000 Wiley-Liss, Inc.
182 citations
TL;DR: Various aspects of management strategies based on the present state of knowledge are discussed, areas for the future research are explored and the various factors affecting tilapia seed output are discussed.
127 citations
TL;DR: The results suggest that the performance of overwintered seed compare well with new-season fry, and monosex fish of the three strains grew significantly faster than mixed-sex fish in ponds.
109 citations
TL;DR: This study demonstrates that objective sperm quality assessments can be made using flow cytometry and that addition of antibiotics at appropriate concentrations can lengthen refrigerated storage time for tilapia spermatozoa.
90 citations
TL;DR: In this paper, the potential impact of culturing the improved Nile tilapia strain in five Asian countries (Bangladesh, China, Philippines, Thailand and Vietnam) was analyzed using a three-step procedure.
Abstract: The International Center for Living Aquatic Resources Management (ICLARM) and its research partners have recently developed a genetically improved Nile tilapia strain. This paper analyzes the potential impact of culturing the improved tilapia strain in five Asian countries (Bangladesh, China, the Philippines, Thailand and Vietnam), using a three‐step procedure. The steps are (1) to develop a model of the fish sector for each country using data from baseline surveys of producers and consumers and from secondary sources, (2) to construct ex ante impact indicators using data collected in on‐farm production trials, and (3) to analyze the impact of the use of the genetically improved Nile tilapia by incorporating the results of on‐farm trials into the fish sector model. The analysis indicates that the use of the genetically improved strain will benefit both producers and consumers offish.
75 citations
01 Jan 2000
TL;DR: An analysis of the global status of cultured tilapias suggests that the lack of an effective strategy for seed production can both weaken efforts to support current farmers raising tilapia and jeopardize successful adoption of improved systems and strains.
Abstract: Tilapias stand alone among the important cultured fish in their singular ability to breed without any special inducement or modification to their environment. But an analysis of the global status of cultured tilapias suggests that the lack of an effective strategy for seed production can both weaken efforts to support current farmers raising tilapias and jeopardize successful adoption of improved systems and strains.
65 citations
TL;DR: Under the conditions tested in this study, seed production and spawning synchrony in the Nile tilapia may be improved by subjecting breeders to a light intensity of 2500 lux and a photoperiod of 18 h day−1.
Abstract: The objective of this study was to compare the effect of six light intensity/photoperiod combinations (2500 lux/18 h, 2500 lux/15 h, 2500 lux/12 h, 500 lux/18 h, 500 lux/15 h and 500 lux/12 h) on seed production in the Nile tilapia Oreochromis niloticus L. Each combination represented a treatment and was triplicated in 0.4-m3 fibreglass tanks within a recirculating water system. Water temperature was maintained at 29.0 ± 1.0 °C. Males and females with mean body weights of 116.8 and 91.6 g, respectively, were stocked at a rate of eight fish/tank with a male to female ratio of 1:3. Seeds (eggs, sac fry and swim-up fry) were collected every 2 weeks. The experiment lasted for a total of 120 days. The results showed that the 2500 lux/18 h treatment produced significantly greater (P < 0.05) total seed/tank (4944), seed kg−1 female day−1 (50.9), seed m−2 day−1 (40.3) and seed/ female day−1 (6.7) than treatments with medium or short photoperiods (15 and 12 h day−1 respectively) or lower light intensity (500 lux). The degree of spawning synchrony and percentage of the sac and swim-up fry stages were significantly higher in the 2500 lux/18 h treatment than in the other treatments. Under the conditions tested in this study, seed production and spawning synchrony in the Nile tilapia may be improved by subjecting breeders to a light intensity of 2500 lux and a photoperiod of 18 h day−1.
60 citations
TL;DR: The People's Republic of China, the Philippines, Thailand, Indonesia and Taiwan account for most farmed tilapia production in Asia and its production has increased from 154,509 t in 1984 to 700,310 t in 1996, with an annual growth rate of 13%.
Abstract: (2000). Socioeconomics of disseminating genetically improved Nile tilapia in Asia: An introduction. Aquaculture Economics & Management: Vol. 4, SOCIOECONOMICS OF TILAPIA CULTURE IN ASIA, pp. 5-11.
60 citations
01 Jan 2000
TL;DR: With increased understanding of their biology and genetics, allied with improvements in management, tilapia have become very important farmed species and O. niloticus and certain hybrids have now become the major cultured Tilapia.
Abstract: Tilapia were first farmed experimentally in Kenya in 1924 (Oreochromis spilurus niger) and in 1937 in Zaire (Oreochromis nyasalapia macrochir and Tilapia rendalli) (reviewed by Chimits, 1955, 1957) The main period of expansion in Africa was in the 1950s and 1960s as the full potential of this group of fish for natural stocking and culture was realized (reviewed by Balarin and Hatton, 1979) At about the same time, tilapia were gaining importance in Asia after the introduction of O mossambicus into Java (Indonesia) pre-1939 (Chimits, 1955) and subsequent introductions from there to many other countries (reviewed by Pullin, 1988) In Africa, farming of tilapia developed but despite the many beneficial characteristics, problems associated with excessive reproduction in ponds and the small size of the fish produced resulted in disillusionment In Asia and Israel farmers persisted with species more suited for culture With increased understanding of their biology and genetics, allied with improvements in management, tilapia have become very important farmed species O niloticus and certain hybrids have now become the major cultured tilapia
52 citations
TL;DR: Analysis showed that transferring muddy-flavored fish to static clean water purged geosmin from the fish but it required at least 16 days to eliminate the muddy flavor, and holding the fish over longer periods in water with higher geosmine content resulted in a greater amount of absorption.
Abstract: The concentration of geosmin (1,10-trans-dimethyl-trans-9-decaol) in fresh tilapia were analyzed by applying high-vacuum distillation, extraction and gas chromatography techniques. The distribution of geosmin in the fish was determined by examining tissues from various parts of tilapia, along with the rates of geosmin absorption and purging. Analysis showed that when geosmin was added to fish flesh at concentrations ranging from 2.8 to 390 μg per kg of flesh, the rate of recovery was 51 to 89%. Sensory evaluation detected muddy flavor in freshwater tilapia with geosmin content ranging from 7.55 to 9.85 μg/kg of fish flesh. However, panelists failed to detect muddy flavor in brackish water tilapia that contained geosmin only in the range of 1.5 to 2.6 μg/kg. Among various tissues of the fish, the intestines contained the highest geosmin concentration, and appeared in descending order in the abdominal, skin and muscle tissues. After holding for 2 h in water with 5 and 50 μg/l geosmin, tilapia absor...
48 citations
TL;DR: In this paper, a comparative analysis of the profile of tilapia fanners and their farming systems, costs, returns and productivity, and fish consumption patterns in Bangladesh, China, the Philippines, Thailand and Vietnam, using data from household surveys conducted by ICLARM.
Abstract: An assessment of the status of production and consumption of tilapia in five Asian countries was made to provide a baseline for the analysis of the potential benefits of the introduction of a new, improved strain of Nile tilapia. This paper provides a comparative analysis of the profile of tilapia fanners and their farming systems, costs, returns and productivity of tilapia production, and fish consumption patterns in Bangladesh, China, the Philippines, Thailand and Vietnam, using data from household surveys conducted by ICLARM and its partners in 1995–96. Farmers grow tilapia in varied farming environments depending on the nature of their farmland and on their investment capacity. Tilapia is cultured mainly in semi‐intensive systems on small and medium farms. The average farm size (pond area) of the surveyed pond operators varies from 0.60 ha (0.05 ha) in Bangladesh to 4.91 ha (1.56 ha) in the Philippines. In Asia, tilapia farming is very profitable. The productivity, costs of production and pro...
TL;DR: Significant differences were observed between treatments, with lower values obtained for fish fed on USB, suggesting a modification in the composition of secreted proteases, and an inhibitory effect produced by wheat bran included in the test diets on protease activity of fish was shown.
Abstract: This study was conducted to evaluate the effect that feeding on differently treated soybean meals may have on digestive protease activity of the Nile tilapia (Oreochromis niloticus) Untreated full fat soybean (USB), heated fullfat soybean (HSB), soaked fullfat soybean (SSB) and commercial defatted soybean meal (DSB) totally replaced fish meal (FM) in test diets (30% crude protein) fed to fish juveniles (mixed sexes) for 30 days After this period, total activity of digestive proteases was determined in each group and the ability of such proteases to hydrolyse the different protein sources and formulated feeds was tested in vitro Significant differences were observed between treatments, with lower values obtained for fish fed on USB, suggesting a modification in the composition of secreted proteases In addition, an inhibitory effect produced by wheat bran included in the test diets on protease activity of fish was also shown The usefulness of using in vitro assays for a preliminary assessment of the nutritive value of aquafeed ingredients is discussed
TL;DR: Hapas-in-ponds are a low-cost overwintering method that can be one of the appropriate strategies for tilapia seed production under the variable, cool temperature regimes in northern Vietnam.
Abstract: Two experiments (E1 and E2) to assess the performance of tilapia broodstock and tilapia sex-reversed fry in overwintering were conducted at the Research Institute for Aquaculture No.1 (RIA-1) in the cold seasons of 1995–96 and 1996–97. Nile tilapia Oreochromis niloticus (L.) broodstock of the Thai, GIFT, Egypt and Viet strains were overwintered in deep and shallow ponds, as well as in deep and shallow hapas suspended in a single deep pond for evaluation of the influence of overwintering systems on the survival and growth of fish. Large (> 1 g) and small (< 1 g) tilapia seed were overwintered in deep hapas-in-ponds for comparison of their performance. In 1995–96, the coldest pond water temperature was 10–11 °C, and survival of tilapia broodfish overwintered in deep and shallow hapas-in-ponds was 99.6–100%. This was significantly (P < 0.05) higher than fish stocked in deep and shallow ponds (74.4–90%). The survival rate of larger monosex tilapia fry was 54%, which was significantly (P < 0.05) higher than that of smaller fry (33.4%). In 1996–97, the lowest pond water temperature was 15.8 °C, and fry showed similarly high survival rates in all treatments (97–100%). There was no significant difference between fry in the two size classes. The results of this study clearly indicate that hapas-in-ponds are useful for reducing the risk and improving the survival of tilapia broodstock and fry in the cold season. Differences in the decline in ambient temperatures year on year mean that the need for special overwintering conditions varies. Hapas-in-ponds are a low-cost overwintering method that can be one of the appropriate strategies for tilapia seed production under the variable, cool temperature regimes in northern Vietnam.
TL;DR: The mean values of hepatosomatic relation, splenosomatic relation (SSR) and relative condition factor (Kn) in Nile tilapia, pacu, piaucu and tambacu hybrid are described and the hepatic weight/body weigth relation and hepatic Weight/body length relation presented positive correlation in studied fishes.
Abstract: The mean values of hepatosomatic relation (HSR), splenosomatic relation (SSR) and relative condition factor (Kn) in Nile tilapia (Oreochromis nilolicus Trewavas, 1983); pacu (Piaractus mesopolamicus Holmberg, 1887); piaucu (Lepori-nus macrocephalus Garavello & Britski, 1988) and tambacu hybrid (P. mesopotamicus male x Colossoma macropomum Cuvier, 1818 female) are described. The experiment was carried out from feefishing farm situated in Franca, Sao Paulo State, Brazil. Nile tilapia showed the greatest HSR compared to pacu, piaucu and tambacu. Although, in the last three fishes the relation was similar. The SSR between tilapia and piausu was similar, but smaller than observed in pacu and tambacu. Nevertheless, SSR in pacu and tambacu was different. The hepatic weight/body weigth relation and hepatic weight/body length relation presented positive correlation in ali studied fishes. The splenic weight/body weigth relation and splenic weight/body length relation were not significam (P>0.05) in Nile tilapia, pacu and tambacu, but highly significant in piaucu (PO.01).
TL;DR: Eight monoclonal antibodies against tilapia immunoglobulins (Ig) were produced and characterized and further analysis indicated that all eight MAbs react withtilapia Ig H chain and cross-reactive with other Tilapia species and their hybrids.
Journal Article•
TL;DR: The mean weight gains at harvest of the GIFT strain was significantly higher (40-57%) than the existing Nile tilapia strain in all the trials.
Abstract: Comparative production performances of Genetically Improved Farmed Tilapia (GIFT) and existing Nile, Oreochromis niloticus L. strains were assessed in five test environments (nursery systems, cisterns, hapas, net cages, and grow-out ponds) and six multi-locational sites (Trishal, Chandina, Manikganj, Paikgacha, Jessore Sadar, and Mithapukur) under on-station and on-farm conditions in Bangladesh. The mean weight gains at harvest of the GIFT strain was significantly higher (40-57%) than the existing Nile tilapia strain in all the trials.
TL;DR: Whereas fish meal had the lowest apparent phosphorus availability among animal foodstuff, soybean meal was the best among plant foodstuffs.
Abstract: Apparent availability of phosphorus from various foodstuffs for sexually reversed Nile tilapia ( Oreochromis niloticus ) was provided. Fish with an average weight of 16.0 0.5g were randomly stocked in 21 aquariums equipped with feces collector ( Guelf system), at the rate of five fish per aquarium. Each set of three aquariums was provided with a biological filter, aeration and flowing water (0.75 L/min discharge). An egg albumin-gelatin purified diet containing 0.1% chromic oxide was used as reference and basal diet. Dicalcium phosphate, bone and fish meals, soybean and wheat bran and middlings were added to the basal diet at 3.5, 6.0, 21.67, 40.0, 12.0 and 10.62% respectively, at the expense of albumin, gelatin and dextrose. Dicalcium phosphate was the best phosphorus source (apparent availability of 74.23%) for tilapia fingerlings. In decreasing order it was followed by bone and soybean meals (54.59 and 35.13%), wheat middlings (30.49%), fish meal (27.15%) and corn meal (7.33%). Whereas fish meal had the lowest apparent phosphorus availability among animal foodstuff, soybean meal was the best among plant foodstuffs.
TL;DR: Parasites and bacterial pathogens of fish at Lake Ziway, during 1996B97 were studied and Edwardsiella tarda, (new geographic record) isolated from the liver of one O. niloticus and kidney of another carp species is known to be pathogenic to fish.
Abstract: Parasites and bacterial pathogens of fish at Lake Ziway, during 1996B97 were studied. A total of 613 fish were sampled. These included 495 Nile tilapia (Oreochromis niloticus), 75 Catfish (Clarias gariepinus), 24 Barbus species, 11 Tilapia zillii and 8 carp species. The fish were thoroughly examined both externally and internally for the presence of parasites and lesions and samples were taken for bacteriological investigations. Among the bacteria, Edwardsiella tarda, (new geographic record) isolated from the liver of one O. niloticus and kidney of another carp species is known to be pathogenic to fish. On the other hand Shigella species, Escherichia coli, Citrobacter, Klebsiella oxytoca, and Yersinia enterocolitica were the major bacteria identified from the apparently healthy fish. The major parasites identified included Contracaecum species from 77 (15.56 %) of O. niloticus, 3 (27.27%) T. zillii, 4 (5.33%) C. gariepinus and 2 (8.33%) Barbus species. Clinostomum species were recovered from the branchial cavity of 45 (9.09%) Oreochromis niloticus, 2 (18.18%) Tilapia zillii and 3 (4.00%) C. gariepinus. Only 1 Euclinostomum species (new geographic record) was recovered from the branchial cavity of O. niloticus. Moreover 13 (17.33%) C. gariepinus were carrying Amplicaecum species in their mesentery and one C. gariepinus was positive to Bothriocephalus species. The significance of these parasites and bacterial pathogens as causes of diseases to fish is discussed. SINET: Ethiopian Journal of Science Vol. 23, No. 1 (June 2000), pp. 25-33
Key words/phrases: Bacteria, Edwardsiella tarda, fish diseases, Lake Ziway, parasites
Journal Article•
01 Jan 2000
TL;DR: Semi-intensive production of tilapia in ponds using fertilizers and supplementary feeds is a means to produce low-cost fish which contributes to national food security in many developing countries and has probably been higher because of considerable underestimation of farmed Tilapia production.
Abstract: Semi-intensive production of tilapia in ponds using fertilizers and supplementary feeds is a means to produce low-cost fish which contributes to national food security in many developing countries. Culture of herbivorous and omnivorous tilapias feeding low down on the food chain provides produce that is potentially available to a wide range of consumers as a staple food. This feature led to tilapia being referred to as an’ aquatic chicken’ (Maclean, 1984). Indeed, global production and value of farmed tilapias increased at a recorded average rate of 11.4 and 15.5% between 1986 and 1995, respectively (FAO, 1997). The rate of increase has probably been higher because of considerable underestimation of farmed tilapia production, particularly in Asia which dominates production, because of the difficulty of collecting statistics from diverse and widely scattered farms in developing countries. Using hatchery data as a proxy for output may be useful for carps and other species produced in conventional hatcheries but as tilapia can breed in food fish production systems this method cannot be used (Little and Hulata, this volume). Tilapias are currently farmed commercially or experimentally in at least 75 countries (Pullin et al, 1994).
TL;DR: In this article, the socioeconomics and production efficiency status of tilapia hatcheries in the Philippines prior to the adoption of the genetically improved Nile-tilapia strain was analyzed and a stochastic frontier production function was specified to examine the levels of farm-specific technical efficiencies.
Abstract: With the recent availability of genetically improved Nile tilapia strain in the Philippines, it is important to look at the existing profile of tilapia hatchery operations in the country to help examine the potential strategies in the dissemination of the improved strain among hatchery operators This paper attempts to analyze the socioeconomics and production efficiency status of tilapia hatcheries in the Philippines prior to the adoption of genetically improved Nile tilapia strain A stochastic frontier production function is specified and estimated to examine the levels of farm‐specific technical efficiencies of tilapia hatchery operation Tilapia hatchery operators in the Philippines have the necessary education, tenure security, and adequate years of experience and are willing to adopt new technologies and better strains if these are made available to them Tilapia hatchery is a highly profitable operation The cost of production per unit of fingerling produced will be higher for the genetic
TL;DR: Sediments from Bahía of Chetumal have the potential to cause histopathological, haematological and biochemical alterations in fish, and the administration of sediment extracts to fish may serve as a useful test to screen the toxicity of sediments from different areas.
TL;DR: The nesting of successive intestinal loops of the spiral intestine in this fish is novel among patterns previously described, and also among the more intricate of those that have been described.
Abstract: The intestinal tract of the Nile tilapia, Oreochromis niloticus L., follows a complex course involving multiple loops and coils arranged in a previously undescribed form. From crani
TL;DR: Results of chi-square tests of the frequency data of males and females after the treatments and of analysis of histological and macroscopic characteristics showed that the numbers of males obtained by A, B, C and D treatments was higher than the control groups and the dose of 60 mg MT/kg of diet, as for the diets 1 and 2, was more efficient, resulting in 98% of males.
Abstract: The objectives of the present study were to compare the efficiency of two diets: 1 (NUTRAVIT) and 2 (IP), both with 40% of crude protein, containing the synthetic androgen hormone 17 a-methyltestosterone (MT) and to analyze the most effective dose of this hormone on the sex reversal of Nile tilapia Oreochromis niloticus, throughout histological analysis of the gonads and sex determination of the samples. A total of 9600 Nile tilapia fries with seven days posthatching received the following treatments, per 45 days period: A- 30 mg MT/kg diet 1; B- 60 mg MT/kg diet 1; C- 30 mg MT/kg diet 2; D- 60 mg MT/kg diet 2 and two control groups, E and F with diets 1 and 2 hormone free, respectively. The results of chi-square tests of the frequency data of males and females after the treatments and of analysis of histological and macroscopic characteristics showed that the numbers of males obtained by A, B, C and D treatments was higher than the control groups and the dose of 60 mg MT/kg of diet, as for the diets 1 and 2, was more efficient, resulting in 98% of males. Among diets, the treatment A with diet 1 was better than the treatment C with diet two, for the dose of30 mg MT/kg of diet. There was no difference among diets for the dose of 60 mg MT/kg of the diet.
TL;DR: In this paper, the masking or reduction of off-flavor in tilapia due to various preservation methods such as salting, drying, frying, smoking, microwave heating, marinating and fermentation with carbohydrate mixture (som fak preparation) was investigated.
Abstract: In this study, the masking or reduction of off-flavor in tilapia due to various preservation methods such as salting, drying, frying, smoking, microwave heating, marinating and fermentation with carbohydrate mixture (som fak preparation) was investigated by subjecting the processed tilapia to sensory evaluation and analyzing the concentrations of geosmin (1,10-trans -dimethyl-trans -9-decaol) in the processed samples. Dry salting or brining muddy-flavored fish and then drying either by hot air at 50°C or sun-drying resulted to only a slight reduction in the geosmin content of the product. Deep-frying reduced the muddy flavor intensity and geosmin content in salted-dried tilapia. Pretreatment of tilapia fillets with acidified brine before smoking reduced geosmin content and masked the muddy flavor in the smoked product. Microwave cooking of fresh muddy-flavored tilapia showed no effect on its geosmin content nor its off-flavor. Marinating tilapia in acetic acid solution resulted in decreased muddy...
TL;DR: Optimal values for vitamin C supplementation of sex reversal diets for the Nile tilapia, derived from polinomial regression analysis procedures, were: weight gain 859.5 mg; growth in length 765.0 mg; and for survival rate 685.7 mg.
Abstract: The effects of vitamin C supplementation (0; 50; 100; 200; 400; 600; 800; 1,000 mg kg-1 of diet) on diets for sex reversal of the Nile tilapia, Oreochromis niloticus, were evaluated on groups of 600 larvae stocked in 0.08 m3 hapas and fed for 30 days with hormone-treated feeds containing different supplementation levels (n=3). Weight gain and total length increment were evaluated after days 0, 10, 20 and 30. Survival rate (S%) and sex reversal rate (SR%) were determined at the end of the experimental period. Weight gain and total length became significantly different only after day 20 (P<0.0001). Best results for weight gain were attained with dietary vitamin C levels above 800 mg kg-1, while the best results for growth in length were attained with dietary vitamin C levels above 400 mg kg-1. Levels of supplementation higher than 200 mg kg-1 did not lead to better survival rates. SR% values were not significantly affected by vitamin C supplementation of sex reversal diets (P<0.9993). Optimal values for vitamin C supplementation of sex reversal diets for the Nile tilapia, derived from polinomial regression analysis procedures, were: weight gain 859.5 mg; growth in length 765.0 mg, and for survival rate 685.7 mg.
TL;DR: The main objective of this research was to determine the effect of water soluble fractions of the Bonny light crude oil on the growth of the Nile tilapia, Oreochromis niloticus.
Abstract: Crude oil spillage during drilling operations, accidental spill during shipping of crude oil and leakages from under ground pipes are becoming a common phenomenon. These have over the years led to polluting the world aquatic ecosystem. The main objective of this research was to determine the effect of water soluble fractions of the Bonny light crude oil on the growth of the Nile tilapia, Oreochromis niloticus. This fish is a conspicuous member of the tropical freshwater system. Several studies document that crude oil and its components inhibit growth of fish. Relatively short, static exposures to water soluble fractions of crude oil or refined oils inhibit growth of larval Baltic herring, Clupea harengus membras (Linden, 1978). Moles et al. (1981) reported that Juveniles coho salmon, Oncorhynchus kisutch had reduced growth after 40-day exposure to 0.67 mL/L naphthalene or 3.18 µL/L toluene (breakdown products of crude oil) in freshwater. Similarly, Woodward et al. (1981) reported that juvenile cut-throat trout Salmo clarki had reduced growth after 60 days
TL;DR: The results of this study indicate that 0.42% of tannin had no effect on dry matter, crude protein and lipid digestibility but 0.63% or higher levels had significant harmful effect on the digestibility of nutrients.
Abstract: This experiment was undertaken to determine the effect of tannin from Stryphnodendron obovatum added to fish diets. The apparent digestibility of dry matter, crude protein and lipid was evaluated. Eighty Nile tilapia juveniles were arranged in five groups (16/aquarium) and fed diets containing 0.00%; 0.21%; 0.42%; 0.63% and 0.84% of total tannin from barbatimao ( Stryphnodendron obovatum ). After three days of acclimatation, feces were collected during 5 days up to reach five replicates/group. The apparent digestibility coefficient was determined based on chemical analyses of feedstuffs and feces using chromic acid as an inert marker. The results of this study indicate that 0.42% of tannin had no effect on dry matter, crude protein and lipid digestibility but 0.63% or higher levels had significant harmful effect on the digestibility of nutrients.
TL;DR: Heat shock treatment of fertilized eggs for 3–4 min applied between 4 min and 27 min after fertilization increased the twinning rate by three or four times over that of unshocked eggs, increasing the likelihood of conjoined twins being observed.
Abstract: Conjoined twins (polyembryonic fish) were observed in batches of blue tilapia Oreochromis aureus (Steindachner) and Nile tilapia O. niloticus (L.) embryos incubated at 28 °C. Heat shock (41.8 °C) treatment of fertilized eggs for 3–4 min applied between 4 min and 27 min after fertilization increased the twinning rate by three or four times over that of unshocked eggs. Two basic morphological variations – ventrally or laterally conjoined twins – were observed. Twins did not survive beyond 21 days after hatching. The proportion of twins in heat-shocked egg batches of both species combined ranged from 0.32% to 0.40%.
TL;DR: The effect of the substitution of 10%, 20% and 30% of the ration by distillery yeast in balanced experimental rations on the development in the breeding of tilapias did not show a harmful effect up to the maximum tested level of 30%, showing that the choice of the yeast in the ration for these fishes depends on the availability and occasional cost.
Abstract: Two hundred and forty 45-day-old fingerlings of Nile tilapia (Oreochromis niloticus), sexually reverted with an initial average weight of 1.25 +/- 0.14 g, distributed in a totally casualized delineation, during 330 days. The effect of the substitution of 10%, 20% and 30% of the ration by distillery yeast (Saccharomiyces cerevisae) in balanced experimental rations on the development in the breeding of tilapias did not show a harmful effect up to the maximum tested level of 30%, showing that the choice of the yeast in the ration for these fishes depends on the availability and occasional cost. The yeast provides fish with good resistance to unfavorable environmental conditions, which could be verified since there were no statistical differences among the treatments with different levels of yeast and the witness. The long growth rate in terms of length and weight can be attributed to the little available space for each specimen, not obeying the limit of populational density, as well as reduction of food ingestion, which coincide with the winter season, above of the absence of natural feeding.