Dietary lipid to carbohydrate ratio and performance of pacu Piaractus mesopotamicus (Holmberg, 1887): digestive enzymes activity, muscle growth dinamics and composition of energy reserves

Abstract

In spite of the species economic importance for Brazilian aquaculture, studies addressing the nutritional requirements of pacu Piaractus mesopotamicus, an omnivorous characin, are far from being complete. This project aims at determining the dietary requirements and the ideal lipid to carbohydrate ratio for juvenile and adult pacu through performance and digestibility assays. Wild-caught fish will samples for determining fatty acid composition of total carcass, fillet and gonadal tissues. Dose-response trials will follow targeting determination of effects of dietary lipid levels and types as sources of essential fatty acids on growth and comparative changes in body composition of juvenile fish. Clinical signs caused by dietary fatty acids deficiency or excess, as well as the capability of elongation of short to long chain fatty acids will also be described if recorded. The best results from the first trial will set grounds for the assessment of dietary levels of carbohydrates and their sources in pelleted and extruded test diets. Feed conversion, feed intake, weight gain, carcass composition, protein efficiency ratio, hepatossomatic index, glycogen and fatty acid profiles in fillet and liver, and nitrogen and energy retention will be used as parameters for evaluation of performance. The assessment and quantification of the dietary requirements of lipids and carbohydrates will also be evaluated by enzyme activity (lipase and amylase), histology of muscle fibers, composition of fatty acids and blood parameters. Trials will be set up in completely randomized design (n = 4) and recorded data will be submitted to ANOVA, tests of comparison of means; segmented regression analysis and polynomial will be used to determine the optimum nutritional and economic viability of dietary carbohydrates and lipids for the production of commercial of pacu. (AU)