Chromium oxide (51Cr2O3 ) used as biological marker was not absorbed by fish / Óxido de crômio (51Cr 2O3 ), usado como marcador biológico, não é absorvido por peixe

The aim of this study was to evaluate the rate absorption of radio-labeled chromium oxide (51Cr2O3), used as biological marker in nutrition studies with Nile tilapia Oreochromis niloticus. An experimental diet with approximately 58 µCi of specific activity of the element was encapsulated and fed daily to 35 adult Nile tilapia; a group of 35 fish was used as control feeding on a basal diet. At the beginning of the experiment five fish from each group were randomly selected and blood samples were drawn from control (BC) and experimental fish (BE). Fish were then euthanized by anesthetic overdoses and samples of the liver tissue (LT), renal tissue (RT), stomach without content (S), intestine without content (I), gills tissue (GT), muscle tissue (fillet; MT), visceral fat (VF), content of the digestive tract (CTDE) and water aquarium were collected from the experimental fish. The procedure was repeated daily for one week. Simple linear regressions were adjusted - days of collection vs. determination coefficients, and were established for statistical comparisons of the measured activity of 51Cr readings in sampled blood and tissues (logarithmic transformation) for samples of the control and experimental fish. No differences (P>0.05) were detected between samples from BC fish and BE, RT, VF, MT and LT of treated fish, but samples of GT, I, S, CTDE and WA from the tanks holding fish which received the experimental diet differed from control (P<0.05). The experimental results indicate that the trivalent chromium in the form of 51Cr2O3 was not significantly absorbed by the gastrointestinal tract, gills or another possible route of absorption under these experimental conditions and with Nile tilapia. Therefore, this marker was shown to be inert and can be safely used in nutrition studies.

O objetivo deste estudo foi avaliar a taxa de absorção de radiomarcador óxido de crômio (51Cr2O3), utilizado como marcador biológico em estudos de nutrição, com tilápia-do-nilo Oreochromis niloticus. Uma dieta experimental com cerca de 58µCi de atividade específica do elemento foi encapsulada, e 35 adultos de tilápia foram alimentados diariamente; um grupo de 35 peixes foi usado como controle e alimentado com uma dieta basal. No início do estudo, cinco peixes de cada grupo foram selecionados aleatoriamente, e amostras de sangue foram coletadas dos peixes controle (BC) e experimentais (BE). Os peixes foram sacrificados por overdose de anestésicos, e amostras do tecido do fígado (LT), rins (RT), estômago sem conteúdo (S), intestino sem conteúdo (I), brânquias (GT), tecido muscular (filé; MT), gordura visceral (VF), conteúdo do trato digestivo (CTDE) e água do aquário (WA) foram coletadas somente dos peixes experimentais. O processo foi repetido diariamente durante uma semana. As regressões lineares simples foram ajustadas - dias de coleta versus coeficientes de determinação - e foram estabelecidas para comparações estatísticas da leitura das atividades medidas de 51Cr (transformação logarítmica) nas amostras dos peixes controle e experimentais. Não foram detectadas diferenças (P>0,05) entre as amostras BC dos peixes controle e BE, RT, VF , MT e LT dos peixes experimentais, mas as amostras de GT, I, S, CTDE e WA dos peixes que receberam a dieta experimental apresentaram diferença significativa em relação aos que receberam a dieta controle (P<0,05). Os resultados experimentais indicam que o crômio trivalente na forma de 51Cr2O3 não foi significativamente absorvido pelo trato gastrointestinal, pelas brânquias ou por outra via possível de absorção nessas condições experimentais e com tilápia do Nilo. Portanto, esse marcador demonstrou ser suficientemente inerte, o que torna seguro seu uso em estudos de nutrição.

Depletion study and estimation of the withdrawal period for enrofloxacin in pacu (Piaractus mesopotamicus).

Defining the pharmacokinetic parameters and depletion intervals for antimicrobials used in fish will help in the development of important guidelines for future regulations by Brazilian agencies on the use of these substances in fish farming. This paper presents a depletion study for enrofloxacin (ENR) and its main metabolite, ciprofloxacin (CIP), in pacu (Piaractus mesopotamicus) fillets. The depletion study was carried out under monitored environmental conditions, with the temperature controlled at 27 °C to mimic the fish farming conditions in Brazil. ENR was administered orally via medicated feed for 10 consecutive days at daily dosages of 10 mg/kg body weight (b.w.). The fish were slaughtered at 6, 12, and 24 h and 2, 3, 5, 8, 12, 17, and 24 days after the medication period. Considering a maximum residue limit of 100 µg/kg for the sum of the ENR and CIP residues in the fillet, the results obtained in the depletion study allowed the estimation of a half-life for ENR of 2.75 days and a withdrawal period of 23 days. The results obtained in this study are important for the farming of pacu in tropical regions.

Growth, body composition and hematology of juvenile pacu (Piaractus mesopotamicus) fed increasing levels of ractopamine / Crescimento, composição corporal e hematologia de juvenis de pacu (Piaractus mesopotamicus) alimentados com quantidades crescentes de ractopamina

The effects of four levels of dietary ractopamine (RAC) on growth, body composition and hematology of pacu, Piaractus mesopotamicus juveniles (103.6±3.3g) were studied. Fish were housed into 12 circular tanks of 1 m3 - 15 fish per tank - and fed for 60 days with practical diets supplemented with 0; 10; 20 or 40mg RAC per kg of diet, in a totally randomized design trial (n=3). Fish fed diets containing up to 40mg RAC/kg diet for 60 days did not have improved growth or body composition parameters. There were no significant differences in hematocrit, hemoglobin and mean corpuscular hemoglobin. Plasma glucose and triglycerides were significantly smaller in fish fed with RAC; however no significant differences between RAC levels were detected. The inclusion of up to 40mg RAC/kg of diet did not improve growth and body composition, but influenced some hematological and biochemical parameters of juvenile pacu.

Estudou-se o efeito de quatro quantidades de ractopamina dietética (RAC) sobre o crescimento, a composição corporal e a hematologia de juvenis de pacu, Piaractus mesopotamicus (103,6±3,3g). Os peixes foram distribuídos em 12 tanques circulares de 1m3 - 15 peixes por tanque - e alimentados por 60 dias com dietas práticas suplementadas com 0, 10, 20 ou 40mg RAC/kg de ração, em um delineamento inteiramente casualizado (n=3). Os peixes alimentados por 60 dias com dietas contendo até 40mg RAC/kg não apresentaram melhora no crescimento ou na composição corporal. Não houve diferença significativa nas concentrações de hematócrito, hemoglobina e hemoglobina corpuscular média. Glicose e triglicerídeos plasmáticos foram significativamente menores nos peixes alimentados com RAC, entretanto não houve diferença significativa entre os níveis de RAC. A inclusão de até 40mg RAC/kg de ração não melhorou o crescimento ou a composição corporal, mas influenciou alguns parâmetros hematológicos e bioquímicos de juvenis de pacu.

Depletion study and estimation of the withdrawal period for oxytetracycline in tilapia cultured in Brazil.

Defining pharmacokinetic parameters and depletion intervals for antimicrobials used in fish represents important guidelines for future regulation by Brazilian agencies of the use of these substances in fish farming. This article presents a depletion study for oxytetracycline (OTC) in tilapias (Orechromis niloticus) farmed under tropical conditions during the winter season. High performance liquid chromatography, with fluorescence detection for the quantitation of OTC in tilapia fillets and medicated feed, was developed and validated. The depletion study with fish was carried out under monitored environmental conditions. OTC was administered in the feed for five consecutive days at daily dosages of 80 mg/kg body weight. Groups of ten fish were slaughtered at 1, 2, 3, 4, 5, 8, 10, 15, 20, and 25 days after medication. After the 8th day posttreatment, OTC concentrations in the tilapia fillets were below the limit of quantitation (13 ng/g) of the method. Linear regression of the mathematical model of data analysis presented a coefficient of 0.9962. The elimination half-life for OTC in tilapia fillet and the withdrawal period were 1.65 and 6 days, respectively, considering a percentile of 99% with 95% of confidence and a maximum residue limit of 100 ng/g. Even though the study was carried out in the winter under practical conditions where water temperature varied, the results obtained are similar to others from studies conducted under controlled temperature.

Efficiency of bioaugmentation in the removal of organic matter in aquaculture systems.

Several techniques are currently used to treat effluents. Bioaugmentation is a new bioremediation strategy and has been employed to improve effluent quality by treating the water during the production process. This technology consists basically of the addition of microorganisms able to degrade or remove polluting compounds, especially organic matter and nutrients. The objective of this study was to assess the effects of bioaugmentation on some parameters of organic matter and on the performance of juvenile tilapias in an intensive aquaculture production system. The combination of two bacterial consortiums in a complete randomized design was employed in a factorial analysis with two factors. Statistical differences between treatments were analyzed by the analysis of variance (ANOVA) and Tukey test at the 5% level. One of the treatments, heterotrophic bacterial supplementation, was able to reduce biochemical oxygen demand (BOD) by 23%, dissolved organic carbon (DOC) by 83.7% and phytoplanktonic biomass by 43%. On the other hand, no damage was done to either the physical-chemical indicators of water quality or to the growth performance of juvenile tilapias assessed in this study.

Feed training of peacock bass (Cichla sp)

The Amazonian cichlid peacock bass (Cichla sp.) is a highly marketable food and sport fish, therefore a suitable species for aquaculture. However, because of its piscivorous feeding preferences, the species does not accept dry feeds voluntarily, turning its intensive culture difficult and costly. This study aimed to wean fingerling peacock bass from inert moist food to dry diets. In a first experiment, 1,134 fingerlings weighting 0.27 g were divided in two 0.37 m³ hapas and fed ground fish flesh with 35 percent success. Then, 1.3 g fish were pooled, stocked in six 25 L cages and fed two pellet sequences with 80 percent, 60 percent, 40 percent, 20 percent and 0 percent ground fish flesh (GFF). One sequence was flavored with 10 percent krill meal (Euphausia sp.). Training success of fish fed the GFF-00 diet flavored with krill reached 12 percentª compared to 11.6 percentª (p < 0.05) for diets without krill meal. A second experiment was set up with 969, 1.5 g fish, trained with GFF with 39.8 percent success. After the feed training period, 2.2 g fish were then fed a sequence of moist pellets containing 80 percent, 60 percent and 45 percent GFF. Fish trained to feed on moist pellets with 45 percent ground fish were pooled and stocked into nine 25 L cages. Fish were weaned to dry pellets without ground fish flesh (GFF-00) using three diet sequences: 1) dry pellets; 2) moist pellets; and 3) dry pellets flavored with 4 percent cod liver oil; all three diets contained 30, 10 and 0 percent GFF. The three sequences yielded, respectively 30.8 percentª, 23.6 percentª, and 24.7 percentª (p < 0.05) fish feeding on GFF-00. There were no apparent beneficial effects of increasing moisture or addition of cod liver oil as flavor enhancers in the weaning diets. This study revealed the feasibility of training peacock bass to accept dry pellets, but feeding young fish ground fish flesh seemed to be a major bottleneck in improving feed training success

Mitogenic activity of fetal bovine serum, fish fry extract, insulin-like growth factor-I, and fibroblast growth factor on brown bullhead catfish cells--BB line

Bioassays were performed to assess the effects of different levels of growth medium supplementation with fetal bovine serum (FBS), fish fry extract (FE), combinations of FBS and FE, and addition of insulin-like growth factor I (IGF-I) and fibroblast growth factor (FGF) on the proliferation of brown bullhead catfish cells (BB line). Treatments (n = 4) were: 2.5, 5, 10, and 15.0 FBS or FE and 5/2.5, 5/5, 10/2.5, and 10/5 of a FBS/FE combination as supplement to the growth medium, or the addition of 0.1, 1, 2.5, 10, 25, and 75 ng/ml of either IGF-I or FGF to the growth media. Initial cell density was 1.1 x 10(6) cells per well on uncoated 24-well plates. Incubation temperature was 29.5 +/- 0.7 degrees C. Six hours after plating, initial culture medium was removed, plates rinsed with Dulbecco's phosphate buffered saline, treatment media added, and cells allowed to proliferate for 24 hours. Another bioassay was performed with rat myoblast omega cells (RMo) using the same levels of growth medium supplemented with FBS, FE and FBS/FE. Base growth medium was Dulbecco's MEM. The initial cell density was 7.2 x 10(6) cells per well, and the bioassay was carried out at 36.0 +/- 0.5 degrees C, on a 95 air, 5 CO2 incubator. Increasing levels of FBS had a positive effect (P < 0.05) on the proliferation of both BB and RMo cells. Increasing levels of FE had a negative effect (P < 0.05) on the proliferation of BB cells and totally inhibited the proliferation of RMo cells at any level of supplementation. Higher levels of FE on the FBS/FE combinations presented a negative effect on the proliferation of both BB and RMo cells (P < 0.05). Insulin-like growth factor I had a positive quadratic effect (P < 0.05) on the proliferation of BB cells. Apparently, mammalian growth factors slightly stimulated mitogenic activity in fish cells, while FE contained factors which inhibited the mitogenic activity of RMo and BB cell lines.