Análise da exigência do aminoácido essencial metionina para juvenis do camarão branco Litopenaeus vannamei (BOONE, 1931), com ênfase sobre os efeitos do sistema de cultivo, alimentação e estratégias nutricionais

Abstract

The shrimp production is diversified around the world; being carried out under different variables resulted from large number of rearing methods and levels of intensification. Thus, there are many environmental variables that can influence the nutritional requirements of farmed shrimps. The present study aimed evaluate the effects of rearing variables such as water exchange regime, feed allowance, stocking density and nutritional strategies over dietary methionine requirement of juveniles Pacific white shrimp, Litopenaeus vannamei. The study was divided into three consecutive phases. The first phase evaluated the effect of water exchange regime, dietary methionine content and their interactions on the growth performance of L. vannamei reared in green water conditions. It was observed that decreasing water exchange rates reduces dependence on higher levels of dietary methionine to maximize shrimp growth. The second phase evaluated the effects of stocking density, feed allowance, dietary methionine content and their interactions on the growth performance of L. vannamei reared in green water conditions. It was observed that with increasing stocking density the shrimp become more dependent on extrinsic food sources and higher amounts of methionine in the diet are required to promote maximum growth. However, dietary requirements for methionine may be reduced as feed rates are increased. The third phase aimed to determine the dietary methionine requirement of L. vannamei juvenile fed with diets formulated based on the ideal protein concept. It was observed from the regression analysis that the optimal dietary methionine value for maximum growth of L. vannamei range from 9.4 to 10.5 g kg-1 of the diet (2.48 to 2,77% of the crude protein), corresponding to the ideal methionine/lysine ratio of 43 and 48%, respectively. The results of the present study evidence that the dietary methionine requirement of juvenile L. vannamei respond according to the production variables, such as rearing conditions, stocking density, and essential amino acids ratios.