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.

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.

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.