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Nutritive value of feedstuffs, dietary protein requirement, and physiological responses of piapara Leporinus obtusidens


Despite the productive potential and demand in piapara (Leporinus obtusidens) both for consumption and for sport fishing, studies about piapara nutrition are very scarce and the nutritional values of feedstuffs are unknown. In the first experiment, the digestibility coefficients of dry matter, protein and energy of feedstuffs used in commercial diets will be determined. High-protein ingredients will be evaluated: tilapia processing by-product meal, poultry by-product meal, feathers and blood meal, meat bone meal, soybean meal, corn gluten and cottonseed meal. Also, high-energy ingredients will be evaluated: sorghum, corn, corn germ, rice bran and wheat bran. For seven days, the fish will receive the test diets and then transferred to aquariums for faeces collection. The results will be submitted to ANOVA and Tukey´s test (5%). In the second experiment, the requirement of digestible protein for piapara juveniles and its effects on the metabolism and nitrogen excretion will be determined. 360 juveniles (15g) will be used, distributed in 24 tanks of 130 L (15 fish/tank). Six isoenergetic diets will be formulated to contain increasing levels of digestible protein (21, 24, 27, 30, 33, 36% PD). After 60 days of feeding, fish will be weighted to evaluate the growth performance and nutrient retention, as well as: concentration of metabolites in the blood, tissue energy reserve indicators, enzymatic activity and indicators of muscle tissue quality. Every three days, the concentration of total ammonia, nitrate and nitrite in the water of the tanks will be determined. The experimental design will be completely randomized, with 6 treatments and 4 replicates. The performance results will be submitted to ANOVA and polynomial regression. The results of physiological indicators and water parameters will be submitted to ANOVA and Tukey's test (5%). (AU)