Relação lipídio:proteína dietética para juvenis de curimatã-pacu (Prochilodus argenteus)

Abstract

The curimatã-pacu (Prochilodus argenteus) is an endemic species from the São Francisco River, and an important fishing resource in this region. However, its natural populations are currently in decline, due to different anthropic actions in its habitat. As a result, production in captivity has emerged as an alternative for preservation and continued supply to the consumer market. Since this is a new species in aquaculture, no studies have been made on nutritional requirements and the necessary conditions for acceptable results in its captive breeding. In general, because proteins are the most costly macronutrients in aquaculture diets, their nutritional requirement is the first to be established for new species used in aquaculture. However, the protein requirements of a species may be influenced by the concentration of dietary lips. Therefore, the objective of this study was to determine the protein requirement of juvenile curimatã-pacu in two concentrations of dietary lipids. For this, eight experimental diets were formulated, associating four levels of crude protein (CP) (20, 25, 30 and 35% CP) and two levels of lipids (LIP) (11 and 15% LIP), making up a completely randomized factorial design (4x2) with three repetitions per treatment. Juvenile curimatã-pacu (initial weight 3.6±0.01g) were randomly distributed in glass aquariums with a capacity of 60L (15 fish/tank) and fed daily at 6% of biomass during ten weeks. The growth performance, nutrient retention, and chemical body and muscle composition were evaluated at the end of the experiment. The results were submitted at two-way ANOVA and, when significant (p≤0.05), they were compared using Duncan’s test. The nutritional requirement was determined through regression analysis. The final global survival rate was 99.6%, which was significantly influenced by the concentration of lipids in the diets. The concentration of CP was the only factor to influence (p≤0.05) weight gain, feed efficiency and the hepatosomatic index of the fish. The requirement for the juvenile curimatã-pacu was estimated at 32% of CP for feed efficiency and 34% CP for weight gain, regardless of the concentration of lipids in the diet. The protein efficiency ratio was only influenced (p≤0.05) by the dietary CP, being inversely proportional to the increase in the CP level of the diet, presenting linear reduction of the increase of dietary CP. The protein retention rate was only influenced (p≤0.05) by dietary proteins. The body lipid content, the liposomatic index and the daily consumption of feed were influenced (p≤0.05) by the interaction between dietary CP x LIP. Therefore, it was possible to conclude that juvenile curimatã-pacu weighing between 3 and 27 g present a CP requirement of 32-34%, with the best protein: energy ratio being 22-23 mg kJ-1.