Níveis de carboidratos e lipídios em dietas para juvenis de tambaqui (Colossoma macropomum): variáveis produtivas, fisiológicas e turnover isotópico
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Data
2016-02-03
Autores
Sandre, Lidiane Cristina Gonçalves de [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
O tambaqui Colossoma macropomum é o peixe nativo brasileiro mais produzido na aquicultura continental de água doce. No entanto, pouco ainda se sabe sobre as exigências qualitativas e quantitativas de nutrientes das espécies nativas utilizadas na aquicultura. Desta forma, o objetivo deste estudo foi avaliar o potencial de utilização de lipídios e carboidratos em dietas para juvenis de tambaqui, por meio de análise do desempenho produtivo, da composição corporal, do metabolismo energético e do turnover isotópico dos nutrientes no músculo, no fígado e na gordura visceral. Na fase pré-experimental, foram utilizados 3.600 juvenis de tambaqui que receberam uma dieta baseada em plantas do ciclo fotossintético C3 por um período de 70 dias, para que os tecidos corporais expressassem a composição isotópica semelhante ao da dieta ofertada. Após esse período, 1080 peixes (com peso aproximado de 10 g) foram distribuídos aleatoriamente em 24 tanques e alimentados com a dieta baseada em plantas do ciclo fotossintético C4, durante 120 dias. O experimento foi realizado com seis tratamentos e quatro repetições em esquema fatorial 3 x 2 constituído por três níveis de extrativo não nitrogenado (41, 46 e 51% ENN) e dois teores de extrato etéreo (4 e 8% EE). O maior nível de inclusão de ENN (51%) causou redução no consumo e, consequentemente, no crescimento dos animais. O incremento no teor de EE para 8% aumentou a deposição de gordura corporal, reduziu os coeficientes de digestibilidade dos nutrientes e da energia, elevou os triglicerídeos séricos e também a gordura do fígado e músculo. Houve efeito poupador de proteína para o crescimento nos tambaquis alimentados com 46% de ENN, uma vez que apresentaram melhores resultados para ganho em peso, taxa de eficiência proteica, eficiência de retenção de proteína bruta e participação da proteína bruta no ganho em peso. O período de experimentação de 120 dias foi suficiente para refletir a composição isotópica das dietas e, pelo δ13C, o músculo foi o tecido que mais evidenciou as diferenças entre as dietas, com o turnover isotópico mais acelerado em animais que receberam as dietas com menores teores de carboidrato (41 e 46%) e lipídios (4%). Para o deutério, os valores isotópicos permitiram a projeção do turnover exponencial e as taxas foram mais aceleradas no fígado e gordura visceral, para as dietas contendo maiores teores de carboidrato e/ ou lipídios. Desta forma, pode-se afirmar que o tambaqui utiliza tão bem os lipídios como os carboidratos para maximização do aproveitamento de proteína. Os resultados indicam que o melhor balanceamento entre os níveis de ENN e EE dietético foi 46% e 4%, respectivamente, sem prejudicar o crescimento e evitar acúmulo excessivo de gordura em juvenis de tambaqui.
The tambaqui Colossoma macropomum is the most produced native fish in Brazil in continental freshwater aquaculture. Little is known, however, about the qualitative and quantitative requirements of nutrients for the native species used in aquaculture. From this context, the objective of this study was to evaluate the potential of using lipids and carbohydrates in diets for juveniles of tambaqui, through the analyses of performance, body composition, energy metabolism, and the isotopic turnover of nutrients in the muscle, liver and visceral fat. In the pre-experimental phase, 3600 tambaqui juveniles were used which received a diet based on plants from the C3 photosynthetic cycle for a period of 70 days, in which the body tissues would express the isotopic signature similar to the offered diet. After this period, 1080 fish (with a weight of approximately 10 g) were randomly distributed into 24 tanks and were fed diets based on plants from the C4 photosynthetic cycle, for 120 days. The experiment was carried out with six treatments and four replications in a 3 x 2 factorial scheme consisted of three levels of nitrogen free extract (41, 46 and 51% NFE) and two levels of ether extract (4 and 8% EE). The highest level of inclusion of the NFE (51%) caused a reduction in the consumption and consequently in the growth of the animals. The increase in the level of EE to 8% increased the deposition of body fat, reduced the coefficients of digestibility of the nutrients and energy, increased serum triglycerides and the fat in liver and muscle. There was a protein-sparing effect for the growth of the tambaquis fed with 46% of NFE, since these animals presented the best results for weight gain, protein efficiency rate, retention efficiency of crude protein, and participation of the crude protein in the weight gain. The experimental period of 120 days was sufficient to reflect the isotopic composition of the diets and, for the δ13C, the muscle was the best tissue to demonstrate the differences between the diets, with a more accelerated isotopic turnover in animals receiving the diets with lower levels carbohydrates (41 and 46%) and lipids (4%). For the deuterium, the isotope values allowed the projection of the exponential isotopic turnover and the rates were more accelerated in the liver and visceral fat, for the diets containing greater levels of carbohydrates and/ or lipids. Thus, the tambaqui can be affirmed to use the lipids as efficiently as carbohydrates to maximize the use of protein. The results indicate that the best balance between the levels of dietary NFE and EE was 46 and 4%, respectively, without impairing growth and avoiding an excessive accumulation of fat in juveniles of tambaqui.
The tambaqui Colossoma macropomum is the most produced native fish in Brazil in continental freshwater aquaculture. Little is known, however, about the qualitative and quantitative requirements of nutrients for the native species used in aquaculture. From this context, the objective of this study was to evaluate the potential of using lipids and carbohydrates in diets for juveniles of tambaqui, through the analyses of performance, body composition, energy metabolism, and the isotopic turnover of nutrients in the muscle, liver and visceral fat. In the pre-experimental phase, 3600 tambaqui juveniles were used which received a diet based on plants from the C3 photosynthetic cycle for a period of 70 days, in which the body tissues would express the isotopic signature similar to the offered diet. After this period, 1080 fish (with a weight of approximately 10 g) were randomly distributed into 24 tanks and were fed diets based on plants from the C4 photosynthetic cycle, for 120 days. The experiment was carried out with six treatments and four replications in a 3 x 2 factorial scheme consisted of three levels of nitrogen free extract (41, 46 and 51% NFE) and two levels of ether extract (4 and 8% EE). The highest level of inclusion of the NFE (51%) caused a reduction in the consumption and consequently in the growth of the animals. The increase in the level of EE to 8% increased the deposition of body fat, reduced the coefficients of digestibility of the nutrients and energy, increased serum triglycerides and the fat in liver and muscle. There was a protein-sparing effect for the growth of the tambaquis fed with 46% of NFE, since these animals presented the best results for weight gain, protein efficiency rate, retention efficiency of crude protein, and participation of the crude protein in the weight gain. The experimental period of 120 days was sufficient to reflect the isotopic composition of the diets and, for the δ13C, the muscle was the best tissue to demonstrate the differences between the diets, with a more accelerated isotopic turnover in animals receiving the diets with lower levels carbohydrates (41 and 46%) and lipids (4%). For the deuterium, the isotope values allowed the projection of the exponential isotopic turnover and the rates were more accelerated in the liver and visceral fat, for the diets containing greater levels of carbohydrates and/ or lipids. Thus, the tambaqui can be affirmed to use the lipids as efficiently as carbohydrates to maximize the use of protein. The results indicate that the best balance between the levels of dietary NFE and EE was 46 and 4%, respectively, without impairing growth and avoiding an excessive accumulation of fat in juveniles of tambaqui.
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Palavras-chave
Carbono, Deutério, Extrativo não nitrogenado, Extrato etéreo, Isótopos estáveis, Metabolismo energético, Carbon, Deuterium, Nitrogen free extract, Ether extract, Stable isotopes, Energy metabolism