Influence of dietary carbohydrate on the metabolism of juvenile Litopenaeus stylirostris

The effect of dietary carbohydrates (CBH) on glucose and glycogen, digestiv e enzymes, ammonia excretion and osmotic pressure and osmotic capacity of L itopenaeus stylirostris juveniles was studied. The increase of CBH, ranging between 1 and 33%, stimulates activities of alpha-amylase and alpha-glucos idase in the hepatopancreas. High levels of glucose in hemolymph and of gly cogen in the hepatopancreas were reached at the highest level of dietary CB H; however, the kinetics of accumulation is different. Shrimps fed with low level of CBH needed 3 h to reached glucose peak, whereas only 1 h is neces sary for high CBH levels. A saturation curve was observed in glycogen level and ol-amylase activity with maximum values in shrimp-fed diets containing 21% CBH. This level could be used to be included as a maximum shrimp dieta ry CBH level. Pre-prandial glycogen levels were observed in shrimp fed a di et containing 1% CBH, indicating an important gluconeogenesis, which affect ed the protein metabolism. The present results show that a diet containing 10% CBH may not be enough to cover the CBH requirement, which could be sati sfied by dietary protein content. The low osmotic capacity observed in shri mp fed on a diet containing 10% CBH coincided with a relatively low post-pr andial nitrogen excretion which reflects a low concentration of amino acids circulating in hemolymph, which affected the osmotic pressure and the osmo tic capacity. These results reflect the high plasticity of shrimp species t o use protein to obtain metabolic energy from food and its limited capacity for processing dietary CBH. (C) 2000 Elsevier Science B.V. All rights rese rved.