Influência do nível proteico das rações sob o desempenho zootécnico de Macrobrachium rosenbergii submetido a diferentes sistemas de cultivo

Abstract

Freshwater shrimp farming is a lucrative way to produce crustaceans. As the main species of freshwater shrimp farmed for commercial fins are Macrobrachium nipponense and Macrobrachium rosenbergii, due to their growing production or success in cultivating these animals is directly linked to the type of system to which they are being used. Thus, some alternative systems have emerged in order to minimize damage to the environment and increase the stocking density of animals, among them the biofloc cultivation (BFT - Biofloc Technology). Given the above, the objective was to evaluate the productive and zootechnical performance of Macrobrachium rosenbergii fed different levels of crude protein in autotrophic system and bioflocks during the nursery phase. The experiment obtained a completely randomized experimental design with a 2x2 factorial arrangement, the first factor being the different culture systems, clear water (AC) and bioflocks (BFT), and the second the protein levels of the diet (35 and 40%). Thus, obtaining the AC35, AC40, BFT35 and BFT40 treatments, with four replications for each treatment, the experiment lasted 80 days. The food offered to the animals was composed of commercial pelleted feed with 35% and 40% crude protein levels, offered three times a day. For water quality monitoring, temperature, dissolved oxygen and pH were measured twice a day (08: 00h and 16: 00h) with the aid of a multiparameter and ammonia, nitrite, nitrate, orthophosphate and sedimentable solids were measured weekly. The zootechnical performance of the shrimps was analyzed by weekly biometrics, where the parameters were measured as: final average weight, weight gain, feed conversion factor, final biomass and mortality. Data were analyzed using two-way variance (ANOVA) followed by the Tukey means comparison test at 5% probability using ASSISTAT version 7.6 software. The water quality variables of the different cultivation system (Biofloco and Água clear) were within the recommended levels for the optimal cultivation of the species. There was no significant effect on final average weight (FW), weight gain (WG) and specific growth rate (TBI); however, there was a significant difference (p <0.05) in relation to crude protein in the conversion factor. (FCA), survival (S) and final biomass (BF). Thus, it is concluded that the use of biofloc cultivation system allows the reduction of crude protein concentrations of the offered diet, without causing damage to the zootechnical performance variables of shrimp Macrobrachium rosenbergii, and may reduce the operating costs of the production system.