Steelhead trout Oncorhynchus mykiss metabolic rate is affected by dietary Aloe vera inclusion but not by mounting an immune response against formalin-killed Aeromonas salmonicida.

The oxygen consumption (MO2) of two groups of 10° C acclimated steelhead trout Oncorhynchus mykiss was measured for 72 h after they were given a 100 µl kg(-1) intraperitoneal injection of formalin-killed Aeromonas salmonicida (ASAL) or phosphate-buffered saline (PBS). In addition, plasma cortisol levels were measured in fish from both groups prior to, and 1 and 3 h after, they were given a 30 s net stress. The first group was fed an unaltered commercial diet for 4 weeks, whereas the second group was fed the same diet but with 0·5% (5 g kg(-1) ) Aloe vera powder added; A. vera has potential as an immunostimulant for use in aquaculture, but its effects on basal and acute phase response (APR)-related metabolic expenditures and stress physiology, are unknown. Injection of ASAL v. PBS had no measurable effect on the MO2 of O. mykiss indicating that the APR in this species is not associated with any net increase in energy expenditure. In contrast, incorporating 0·5% A. vera powder into the feed decreased routine metabolic rate by c. 8% in both injection groups and standard metabolic rate in the ASAL-injected group (by c. 4 mg O2 kg(-1) h(-1) ; 5%). Aloe vera fed fish had resting cortisol levels that were approximately half of those in fish on the commercial diet (c. 2·5 v. 5·0 ng ml(-1) ), but neither this difference nor those post-stress reached statistical significance (P > 0·05).

Disease resistance of pacu Piaractus mesopotamicus (Holmberg, 1887) fed with ß-glucan.

Effects of ß-glucan on innate immune responses and survival were studied in pacu experimentally infected with Aeromonas hydrophila. Fish fed diets containing 0, 0.1% and 1% ß-glucan were injected with A. hydrophila. ß-glucan enhanced fish survival in both treated groups (26.7% and 21.2% of the control, respectively). Leukocyte respiratory burst and alternative complement pathway activities were elevated after bacterial challenge regardless the ß-glucan concentration. Lysozyme activity was higher after infection and showed a gradual increase as ß-glucan concentration increased. A significant elevation in WBC count was observed either after bacterial challenge or by influence of ß-glucan separately. The same response was observed in the number of thrombocytes, lymphocytes, eosinophils, LG-PAS positive cell and monocytes. It can be concluded that feeding pacu with ß-glucan can increase protection against A. hydrophila, due to changes in non-specific immune responses.

Disease resistance of pacu Piaractus mesopotamicus (Holmberg, 1887) fed with B-glucan / Resistência à doença em pacu, Piaractus mesopotamicus (Holmberg, 1887), alimentados com B-glucana

Effects of β-glucan on innate immune responses and survival were studied in pacu experimentally infected with Aeromonas hydrophila. Fish fed diets containing 0, 0.1% and 1% β-glucan were injected with A. hydrophila. β-glucan enhanced fish survival in both treated groups (26.7% and 21.2% of the control, respectively). Leukocyte respiratory burst and alternative complement pathway activities were elevated after bacterial challenge regardless the β-glucan concentration. Lysozyme activity was higher after infection and showed a gradual increase as β-glucan concentration increased. A significant elevation in WBC count was observed either after bacterial challenge or by influence of β-glucan separately. The same response was observed in the number of thrombocytes, lymphocytes, eosinophils, LG-PAS positive cell and monocytes. It can be concluded that feeding pacu with β-glucan can increase protection against A. hydrophila, due to changes in non-specific immune responses.(AU)

Os efeitos da β-glucana sobre as respostas imunes inatas e a sobrevivência foram estudados em pacu experimentalmente infectado com Aeromonas hydrophila. Peixes alimentados com dietas contendo 0,1% e 1% de β-glucana foram injetados com 1 × 108 CFU de A. hydrophila após 7 dias de alimentação. A sobrevivência de peixes foi maior nos dois grupos tratados em comparação ao grupo controle (26,7% e 21,2%, respectivamente). A atividade respiratória de leucócitos e a atividade hemolítica do complemento via alternativa estavam elevadas após desafio bacteriano independentemente da concentração de β-glucana. A atividade de lisozima foi maior após a infecção e mostrou um aumento gradual de acordo com a concentração do imunoestimulante. Observou-se um aumento significativo na contagem de leucócitos totais após o desafio bacteriano e influência de β-glucana. A mesma resposta foi observada para trombócitos, linfócitos, eosinófilos, leucócito PAS positivo e monócitos. Com exceção de neutrófilos, que diminuíram frente ao mais alto nível do imunoestimulante e não se alteraram após a infecção, as outras células aumentaram após a exposição à A. hydrophila. A β-glucana não afetou os níveis de proteína total do soro, que aumentaram após o desafio bacteriano. Conclui-se que a administração de β-glucana em pacu pode aumentar a proteção contra A. hydrophila, por alterações nas respostas imunes de não-específicas.(AU)

Proposed method for agglutinating antibody titer analysis and its use as indicator of acquired immunity in pacu, Piaractus mesopotamicus.

Antibody can be assessed by agglutinating antibody titer which is a quantitative measure of circulating antibodies in serum from fish previously immunized. The antibody evaluation has been performed with different fish species, and is considered a reliable method that can be applied to confirm several hypothesis regarding acquired immunity, even in conjunction with precise methods to describe immune mechanisms. In order to provide appropriate analytical methods for future studies on the specific immune system of native fish, the present study standardized on assay to measure the serum agglutinating antibody titer produced after immunization with inactivated A. hydrophila and levamisole administration in pacu. It was possible to determine the agglutinating antibodies titer in a satisfactorily way in pacu immunized with inactive A. hydrophila, and the highest titers were observed on fish fed with levamisole.

Proposed method for agglutinating antibody titer analysis and its use as indicator of acquired immunity in pacu, Piaractus mesopotamicus / Aglutinante de anticorpos como indicador de imunidade adquirida de pacu Piaractus mesopotamicus

Antibody can be assessed by agglutinating antibody titer which is a quantitative measure of circulating antibodies in serum from fish previously immunized. The antibody evaluation has been performed with different fish species, and is considered a reliable method that can be applied to confirm several hypothesis regarding acquired immunity, even in conjunction with precise methods to describe immune mechanisms. In order to provide appropriate analytical methods for future studies on the specific immune system of native fish, the present study standardized on assay to measure the serum agglutinating antibody titer produced after immunization with inactivated A. hydrophila and levamisole administration in pacu. It was possible to determine the agglutinating antibodies titer in a satisfactorily way in pacu immunized with inactive A. hydrophila, and the highest titers were observed on fish fed with levamisole.(AU)

Os anticorpos podem ser avaliados pelo título aglutinante de anticorpos, que é uma medida quantitativa de anticorpos no soro de peixe previamente imunizados. A determinação do título de anticorpos foi realizada com diversas espécies de peixes e é considerado um método confiável que pode ser aplicado para confirmar diversas hipóteses que envolvam o sistema adquirido de defesa, mesmo em conjunto com métodos precisos, para descrever mecanismos imunes. A fim de prover métodos analíticos adequados para futuros estudos sobre o sistema imune específico de peixes nativos, o presente estudo aperfeiçoou o ensaio para avaliar o título aglutinante de anticorpos em soro de pacu imunizados com A. hydrophila e alimentados com levamisol. Foi possível determinar o título aglutinante de anticorpos de forma satisfatória, em pacus imunizados com A. hydrophila inativa, e os maiores títulos foram observados em peixes alimentados com levamisol.(AU)

The time course of aggressive behaviour in juvenile matrinxã Brycon amazonicus fed with dietary L-tryptophan supplementation.

This study evaluated the influence of dietary L-tryptophan (TRP) supplementation on the time course of aggressive behaviour and on neuroendocrine and hormonal indicators in juvenile matrinxã Brycon amazonicus. Supplementation with TRP promoted a change in the fight pattern at the beginning of an interaction with an intruder, resulting in decreased aggressive behaviours during the first 20 min. The decrease in aggression did not persist throughout the interaction but increased at 3 and 6 h after the beginning of the fight. Monoamine levels in the hypothalamus were not influenced by TRP before or after the fight; however, the hypothalamic serotonin (5-HT) concentration and the 5-hydroxyindole-3-acetic acid (5HIAA):5-HT ratio were significantly correlated with the reduction in aggressive behaviour at the beginning of the fight. Cortisol was not altered by TRP before the fight. After the fight cortisol increased to higher levels in B. amazonicus fed with supplementary TRP. These results indicate that TRP supplementation alters the aggressive behaviour of B. amazonicus and that this effect is limited to the beginning of the fight, suggesting a transient effect of TRP on aggressive behaviour. This is the first study reporting the effects of TRP supplementation on the time course of aggressive interaction in fishes.

Serum bactericidal activity as indicator of innate immunity in pacu Piaractus mesopotamicus (Holmberg, 1887) / Atividade bactericida do soro como indicador de imunidade inata de pacu Piaractus mesopotamicus (Holmberg, 1887)

The immune system of teleost fish has mechanisms responsible for the defense against bacteria through protective proteins in several tissues. The protein action can be evaluated by serum bactericidal activity and this is an important tool to analyze the immune system. Pacu, Piaractus mesopotamicus, is one of the most important fish in national aquaculture. However there is a lack of studies on its immune responses. In order to standardize and assess the accuracy of the serum bactericidal activity assay, fish were briefly challenged with Aeromonas hydrophila and sampled one week after the challenge. The bacterial infection increased the concentration of protective proteins, resulting in a decrease of colony-forming unit values expressed as well as an enhanced serum bactericidal activity. The protocol showed a reliable assay, appropriate to determine the serum bactericidal activity of pacu in the present experimental conditions.(AU)

O sistema imune de peixes teleósteos tem mecanismos responsáveis pela defesa contra bactérias e atua através de proteínas presentes em diversos tecidos. A ação destas proteínas pode ser avaliada pela atividade bactericida do soro, sendo esta uma importante ferramenta para analisar o sistema imune. O pacu, Piaractus mesopotamicus, é um peixe nativo muito importante para aquicultura nacional, entretanto há pouco conhecimento sobre o funcionamento de seu sistema imune. Assim foi realizado experimento para padronizar e avaliar a eficiência do ensaio de atividade bactericida. Resumidamente, peixes foram desafiados por Aeromonas hydrophila e amostradas uma semana após o desafio. A infecção bacteriana promoveu um aumento na concentração de proteínas protetoras, resultando em diminuição dos valores de unidades formadoras de colônias ou expressos também como aumento da atividade bactericida do soro. O protocolo se mostrou confiável, sendo apropriado para determinar a atividade bactericida do soro de pacu nas condições experimentais.(AU)

Serum bactericidal activity as indicator of innate immunity in pacu Piaractus mesopotamicus (Holmberg, 1887) / Atividade bactericida do soro como indicador de imunidade inata de pacu Piaractus mesopotamicus (Holmberg, 1887)

The immune system of teleost fish has mechanisms responsible for the defense against bacteria through protective proteins in several tissues. The protein action can be evaluated by serum bactericidal activity and this is an important tool to analyze the immune system. Pacu, Piaractus mesopotamicus, is one of the most important fish in national aquaculture. However there is a lack of studies on its immune responses. In order to standardize and assess the accuracy of the serum bactericidal activity assay, fish were briefly challenged with Aeromonas hydrophila and sampled one week after the challenge. The bacterial infection increased the concentration of protective proteins, resulting in a decrease of colony-forming unit values expressed as well as an enhanced serum bactericidal activity. The protocol showed a reliable assay, appropriate to determine the serum bactericidal activity of pacu in the present experimental conditions.

O sistema imune de peixes teleósteos tem mecanismos responsáveis pela defesa contra bactérias e atua através de proteínas presentes em diversos tecidos. A ação destas proteínas pode ser avaliada pela atividade bactericida do soro, sendo esta uma importante ferramenta para analisar o sistema imune. O pacu, Piaractus mesopotamicus, é um peixe nativo muito importante para aquicultura nacional, entretanto há pouco conhecimento sobre o funcionamento de seu sistema imune. Assim foi realizado experimento para padronizar e avaliar a eficiência do ensaio de atividade bactericida. Resumidamente, peixes foram desafiados por Aeromonas hydrophila e amostradas uma semana após o desafio. A infecção bacteriana promoveu um aumento na concentração de proteínas protetoras, resultando em diminuição dos valores de unidades formadoras de colônias ou expressos também como aumento da atividade bactericida do soro. O protocolo se mostrou confiável, sendo apropriado para determinar a atividade bactericida do soro de pacu nas condições experimentais.

Leukocytes respiratory burst activity as indicator of innate immunity of pacu Piaractus mesopotamicus.

The present study evaluated the assay to quantify the respiratory burst activity of blood leukocytes of pacu as an indicator of the innate immune system, using the reduction of nitroblue tetrazolium (NBT) to formazan as a measure of the production of reactive oxygen species (ROS). In order to assess the accuracy of the assay, fish were challenged by Aeromonas hydrophila and sampled one week after challenge. The A. hydrophila infection increased the leukocyte respiratory burst activity. The protocol showed a reliable and easy assay, appropriate to determine the respiratory burst activity of blood leukocytes of pacu, a neotropical fish, in the present experimental conditions.

Leukocytes respiratory burst activity as indicator of innate immunity of pacu Piaractus mesopotamicus / Atividade respiratória de leucócitos como indicador de imunidade inata de pacu (Piaractus mesopotamicus)

The present study evaluated the assay to quantify the respiratory burst activity of blood leukocytes of pacu as an indicator of the innate immune system, using the reduction of nitroblue tetrazolium (NBT) to formazan as a measure of the production of reactive oxygen species (ROS). In order to assess the accuracy of the assay, fish were challenged by Aeromonas hydrophila and sampled one week after challenge. The A. hydrophila infection increased the leukocyte respiratory burst activity. The protocol showed a reliable and easy assay, appropriate to determine the respiratory burst activity of blood leukocytes of pacu, a neotropical fish, in the present experimental conditions.(AU)

O presente estudo avaliou o ensaio para quantificar a atividade respiratória dos leucócitos do sangue de pacu como um indicador do sistema imune inato, usando a redução do nitroazul tetrazólio (NBT) a formazan como medida da produção de espécies reativas de oxigênio (EROs). Para avaliar a precisão do ensaio, peixes foram desafiados por Aeromonas hydrophila e amostrados uma semana após o desafio. A infecção com A. hydrophila aumentou a atividade respiratória dos leucócitos. O protocolo se mostrou confiável e de fácil aplicação, apropriado para determinar a atividade respiratória de leucócitos do sangue do pacu, peixe neotropical, nas condições experimentais apresentadas.(AU)

HEMAGGLUTINATION ANTIBODY TITERS IN PACU, Piaractus mesopotamicus, AS AN INDICATOR OF ACQUIRED IMMUNITY/Título de anticorpos hemaglutinantes de Pacu, Piaractus mesopotamicus, como indicador de imunidade adquirida

A determinação do título de hemaglutinação é uma alternativa para avaliar as respostas do sistema imune adquirido, ou seja, analisar a capacidade de produção de anticorpos circulantes do organismo. O estudo foi realizado a fim de padronizar a titulação de anticorpos produzidos contra hemáceas de coelho em peixes previamente imunizados e submetidos a dietas com diferentes concentrações de levamisol (0, 250 e 500 mg.kg-1 de levamisol). O resultado é um aglomerado celular que pode ser visualizado a olho nu. Peixes do presente estudo alimentados com 250 mg.kg-1 de levamisol apresentaram maiores títulos de anticorpos hemaglutinantes, entretanto os alimentados com 500 mg.kg-1 apresentaram títulos semelhantes ao grupo controle, alimentado com dieta sem levamisol. Este estudo validou a metodologia para determinação do título de hemaglutinação do soro de peixe nativo imunizados, após administração de levamisol e verificou um aumento da concentração de anticorpos hemaglutinantes após administração de 250 mg.kg-1 de levamisol por 10 dias. SUMMARY  T

HEMAGGLUTINATION ANTIBODY TITERS IN PACU, Piaractus mesopotamicus, AS AN INDICATOR OF ACQUIRED IMMUNITY/Título de anticorpos hemaglutinantes de Pacu, Piaractus mesopotamicus, como indicador de imunidade adquirida

A determinação do título de hemaglutinação é uma alternativa para avaliar as respostas do sistema imune adquirido, ou seja, analisar a capacidade de produção de anticorpos circulantes do organismo. O estudo foi realizado a fim de padronizar a titulação de anticorpos produzidos contra hemáceas de coelho em peixes previamente imunizados e submetidos a dietas com diferentes concentrações de levamisol (0, 250 e 500 mg.kg-1 de levamisol). O resultado é um aglomerado celular que pode ser visualizado a olho nu. Peixes do presente estudo alimentados com 250 mg.kg-1 de levamisol apresentaram maiores títulos de anticorpos hemaglutinantes, entretanto os alimentados com 500 mg.kg-1 apresentaram títulos semelhantes ao grupo controle, alimentado com dieta sem levamisol. Este estudo validou a metodologia para determinação do título de hemaglutinação do soro de peixe nativo imunizados, após administração de levamisol e verificou um aumento da concentração de anticorpos hemaglutinantes após administração de 250 mg.kg-1 de levamisol por 10 dias. SUMMARY  T

The administration of exogenous prostaglandin may improve ovulation in pacu (Piaractus mesopotamicus).

Based on the reports of unsuccessful ovulation in pacu (Piaractus mesopotamicus) by fish farmers and researchers undertaking artificial reproduction programs, we evaluated the use of prostaglandin F (PGF) to improve pacu ovulation. This study was conducted during two spawning seasons (2009/2010 and 2010/2011) with two samplings in the first season and one sampling in the second season. A total of 45 females was sampled in this study. The control group was injected with carp pituitary extract (crude extract, 6 mg/kg), and the treatment group received PGF (2 mL per fish in the 2009/2010 season and 5 mL per fish in the 2010/2011 season) in addition to the crude extract. In both seasons, 100% (N = 4, 2009/2010 first sampling; N = 5, 2009/2010 second sampling; and N = 3, 2010/2011) of the PGF-treated fish spawned. In contrast, 53.0% (N = 9) and 83.3% (N = 10) of the control fish spawned in the first and second samplings of the 2009/2010 season, respectively, and only 25.0% (N = 1) spawned in the 2010/2011 season. Fecundity, fertility, and hatching rates did not differ (P > 0.05) between the treated and control fish. Based on oocyte volume frequency analysis, ovaries of the control fish had more (P < 0.05) vitellogenic oocytes with germinal vesicle breakdown that remained unovulated after spawning, whereas more (P < 0.05) of previtellogenic oocytes were present in the ovaries of the PGF-treated fish. In conclusion, administration of exogenous prostaglandin may improve the outcome of hormonally induced spawning in tropical migratory fish.

Fontes de fibra na alimentação do pacu: desempenho, composição corporal e morfometria intestinal / Pacu fed different fiber sources: performance, corporal composition and intestinal morphometry

O objetivo deste estudo foi avaliar os efeitos da utilização de diferentes ingredientes fibrosos nas dietas sobre o desempenho, a composição corporal e a morfometria intestinal de juvenis de pacu. Foram avaliadas cinco dietas isoproteicas (23 por cento de proteína digestível), isoenergéticas (3250kcal de energia digestível/kg) e isofibrosas (9 por cento de fibra bruta), sendo a principal fonte fibrosa de cada constituída por farelo de soja, casca de soja, farelo de girassol e polpa cítrica; esta última em dois níveis de inclusão (30 e 45 por cento). Foram utilizados 300 juvenis de pacu (25,12±0,78 gramas), alojados em 25 aquários (200 litros). Os melhores resultados de crescimento e conversão alimentar foram obtidos com as dietas contendo farelo de soja e farelo de girassol. As dietas contendo casca de soja e polpa cítrica prejudicaram o desempenho dos juvenis de pacu, e o efeito negativo foi acentuado com o aumento da inclusão de polpa cítrica. Além disto, somente nos peixes alimentados com a dieta com 45 por cento de polpa cítrica foi observada diminuição na densidade de vilosidades por área no epitélio intestinal. A partir dos resultados obtidos, pode-se concluir que alguns ingredientes fibrosos podem afetar negativamente o desempenho e as características do epitélio intestinal de juvenis de pacu.(AU)

The aim of this study was to evaluate the effects of diets containing different fiber sources on the performance, corporal composition and intestinal morphometry of pacu juveniles (Piaractus mesopotamicus). This study evaluated five isoproteic (23 percent digestible protein), isoenergetic (3250kcal digestible energy/kg) and isofibrous (9 percent crude fiber) diets, each one containing a fiber source such as soybean meal, soybean hulls, sunflower meal and citric pulp in two levels of inclusion (30 and 45 percent). A total of 300 pacu juveniles (25,12±0,78g) were stocked in 25 experimental aquariums (200 liters) equipped with aeration and heating system. The best growth and feed conversion results were obtained with diets containing soybean meal and sunflower meal. Diets containing soybean hulls and citrus pulp worsened the juvenile pacu performance. Moreover, only the diet containing 45 percent citrus pulp decreased the villous number per area in the intestinal epithelium. From the results we can conclude that some fibrous ingredient may affect juvenile pacu performance, corporal composition and intestinal epithelium characteristics.(AU)

Fontes de fibra na alimentação do pacu: desempenho, composição corporal e morfometria intestinal / Pacu fed different fiber sources: performance, corporal composition and intestinal morphometry

O objetivo deste estudo foi avaliar os efeitos da utilização de diferentes ingredientes fibrosos nas dietas sobre o desempenho, a composição corporal e a morfometria intestinal de juvenis de pacu. Foram avaliadas cinco dietas isoproteicas (23 por cento de proteína digestível), isoenergéticas (3250kcal de energia digestível/kg) e isofibrosas (9 por cento de fibra bruta), sendo a principal fonte fibrosa de cada constituída por farelo de soja, casca de soja, farelo de girassol e polpa cítrica; esta última em dois níveis de inclusão (30 e 45 por cento). Foram utilizados 300 juvenis de pacu (25,12±0,78 gramas), alojados em 25 aquários (200 litros). Os melhores resultados de crescimento e conversão alimentar foram obtidos com as dietas contendo farelo de soja e farelo de girassol. As dietas contendo casca de soja e polpa cítrica prejudicaram o desempenho dos juvenis de pacu, e o efeito negativo foi acentuado com o aumento da inclusão de polpa cítrica. Além disto, somente nos peixes alimentados com a dieta com 45 por cento de polpa cítrica foi observada diminuição na densidade de vilosidades por área no epitélio intestinal. A partir dos resultados obtidos, pode-se concluir que alguns ingredientes fibrosos podem afetar negativamente o desempenho e as características do epitélio intestinal de juvenis de pacu.

The aim of this study was to evaluate the effects of diets containing different fiber sources on the performance, corporal composition and intestinal morphometry of pacu juveniles (Piaractus mesopotamicus). This study evaluated five isoproteic (23 percent digestible protein), isoenergetic (3250kcal digestible energy/kg) and isofibrous (9 percent crude fiber) diets, each one containing a fiber source such as soybean meal, soybean hulls, sunflower meal and citric pulp in two levels of inclusion (30 and 45 percent). A total of 300 pacu juveniles (25,12±0,78g) were stocked in 25 experimental aquariums (200 liters) equipped with aeration and heating system. The best growth and feed conversion results were obtained with diets containing soybean meal and sunflower meal. Diets containing soybean hulls and citrus pulp worsened the juvenile pacu performance. Moreover, only the diet containing 45 percent citrus pulp decreased the villous number per area in the intestinal epithelium. From the results we can conclude that some fibrous ingredient may affect juvenile pacu performance, corporal composition and intestinal epithelium characteristics.

Feeding strategy with alternate fasting and refeeding: effects on farmed pacu production.

A 36-day trial was conducted to determine the effects of repetitive periods of food restriction and refeeding on growth and energy metabolism in pacu (Piaractus mesopotamicus). A total 264 juvenile fish (36.9±2.8 g) were fed with the experimental diet for 36 days using three regimes: (i) feeding daily to satiation (FD); (ii) no feed for 3 days, then feeding the same amount offered to the control groups for the next 3 days (NF/R controlled); and (iii) no feed for 3 days, then feeding to apparent satiation for the next 3 days (NF/R at satiation). The treatments were distributed into four tanks each. WG and SGR were higher in FD group. Fish refed showed hyperphagia just up to the second day of refeeding. The worst feed conversion rate and the lowest protein efficiency ratio were found in fish NF/R controlled. The lowest values of visceral fat somatic index were found in both fasted fish groups, particularly in NF/R at satiation. The LL and glycogen concentrations, and the hepatosomatic index were all elevated in both feed restricted fish. Muscle lipid showed a tendency to decrease after the cycle of fasting and refeeding. Plasma free fatty acids and glucose levels were elevated in fish subjected to feeding restrictions while serum triglycerides levels were reduced. Triiodothyronine levels were significantly depressed in fish from the NF/R-controlled group and remained at the same levels as the control fish in fish NF/R at satiation. Results indicated that fish subjected to cyclic periods of 3-day satiation or controlled feeding after 3-days of fasting were unable to achieve the final body weight of fish fed to satiation after 36 days.

Fontes de fibra na alimentação do pacu: desempenho, composição corporal e morfometria intestinal

The aim of this study was to evaluate the effects of diets containing different fiber sources on the performance, corporal composition and intestinal morphometry of pacu juveniles (Piaractus mesopotamicus). This study evaluated five isoproteic (23% digestible protein), isoenergetic (3250kcal digestible energy/kg) and isofibrous (9% crude fiber) diets, each one containing a fiber source such as soybean meal, soybean hulls, sunflower meal and citric pulp in two levels of inclusion (30 and 45%). A total of 300 pacu juveniles (25,12±0,78g) were stocked in 25 experimental aquariums (200 liters) equipped with aeration and heating system. The best growth and feed conversion results were obtained with diets containing soybean meal and sunflower meal. Diets containing soybean hulls and citrus pulp worsened the juvenile pacu performance. Moreover, only the diet containing 45% citrus pulp decreased the villous number per area in the intestinal epithelium. From the results we can conclude that some fibrous ingredient may affect juvenile pacu performance, corporal composition and intestinal epithelium characteristics.

O objetivo deste estudo foi avaliar os efeitos da utilização de diferentes ingredientes fibrosos nas dietas sobre o desempenho, a composição corporal e a morfometria intestinal de juvenis de pacu. Foram avaliadas cinco dietas isoproteicas (23% de proteína digestível), isoenergéticas (3250kcal de energia digestível/kg) e isofibrosas (9% de fibra bruta), sendo a principal fonte fibrosa de cada constituída por farelo de soja, casca de soja, farelo de girassol e polpa cítrica; esta última em dois níveis de inclusão (30 e 45%). Foram utilizados 300 juvenis de pacu (25,12±0,78 gramas), alojados em 25 aquários (200 litros). Os melhores resultados de crescimento e conversão alimentar foram obtidos com as dietas contendo farelo de soja e farelo de girassol. As dietas contendo casca de soja e polpa cítrica prejudicaram o desempenho dos juvenis de pacu, e o efeito negativo foi acentuado com o aumento da inclusão de polpa cítrica. Além disto, somente nos peixes alimentados com a dieta com 45% de polpa cítrica foi observada diminuição na densidade de vilosidades por área no epitélio intestinal. A partir dos resultados obtidos, pode-se concluir que alguns ingredientes fibrosos podem afetar negativamente o desempenho e as características do epitélio intestinal de juvenis de pacu.

The influence of triiodothyronine (T3) on the early development of piracanjuba (Brycon orbignyanus).

This paper reports the triiodothyronine's (T3) effects on the early growth and survival of piracanjuba (Brycon orbignyanus) produced from fertilized eggs hormone exposed. The study was carried out in two phases. In the first phase, eggs divided in 6 batches were immersed in T3 solutions: 0.01; 0.05; 0.1; 0.5 ppm; 1 ppm and control (no T3). After a 15-min immersion, eggs were transferred to incubators where larvae were kept up to 72 h after hatching. Larval weight, length and yolk sac volume were determined every 12 h. Sixty and 72 h after hatching, larvae exposed to 0.5 ppm T3 were significantly heavier than the others, and those exposed to 1 ppm T3 showed the lowest weight. The yolk sac absorption was not affected. In the second experimental phase, the resulting fry from the first phase were stocked into 3 boxes per treatment (5 larvae L(-1)) and fed with plankton, fish larvae and feed prepared in the hatchery (48% CP) in the first 3 days, plankton and feed from the 4th to the 10th day and only feed in the next (last) 5 days. Fry weight, length and specific growth rate were determined at 1, 5, 10 and 15 days. Survival was calculated in the last day. In the 15th day, fry length did not differ among treatments but the weight of the control group was higher. Higher survival in the T3-treated groups suggested lower predation among fry. The results allowed us to conclude that there was no expressive effect of T3 on the growth, but it improved the survival of the piracanjuba progeny.

Leukocytes respiratory burst and lysozyme level in pacu (Piaractus mesopotamicus Holmberg, 1887).

Innate immune responses are useful to determine the health status of fish and to evaluate the effect of immunomodulatory substances in fish farming. Leukocytes respiratory burst was measured in pacu (Piaractus mesopotamicus) using chemiluminescence assay and nitroblue tetrazolium (NBT) reduction assay. The nitroblue tetrazolium reduction seemed more adequate than chemiluminescence assay for leukocytes oxidative burst determination, since it was difficult to isolate the blood leucocytes for chemiluminescence assay. Plasma and serum lysozyme were measured using a turbidimetric assay. The heating of serum and plasma samples (56 masculineC for 30 minutes) for complement system inactivation darkened the plasma samples and interfered in the results. The lysozyme activity in serum was higher than in plasma, suggesting that serum samples are more appropriate for the analysis. This study established protocols that can be useful tools in the study of immune mechanisms of the tropical fish pacu.