Dietary protein levels for juvenile matrinxã Brycon amazonicus produced in biofloc and clear water systems

This study evaluated potential for rearing the matrinxã, Brycon amazonicus , under different crude protein (CP) levels, using production performance, water quality and animal welfare as indicators. To achieve this, 720 juvenile fish (3.65 ± 0.17 g) were distributed across 24 experimental units (200 L) and fee study lasted 60 days. The study followed a factorial design (2x4), with two production systems: Biofloc technology (BFT) and clear water (CW), and four levels of crude protein (CP = 24%, 30%, 36%, and 42%) in the diet, with three repetitions for each. The study found that the BFT system showed a lower total ammonia level. However, the production system did not have any effect on pH or nitrite concentration. Oxygen levels were found to be lower in the 42% CP group. Fish produced in the BFT exhibited better performance of apparent feed conversion, productivity, and survival. The production system affected total leukocytes and neutrophils in the blood. There was no significant difference in carcass crude protein content and the ether extract content was higher in the animals from the BFT system. Nutritional composition of the biofloc showed differences for ash, with lower levels in the 42% CP treatment. In conclusion, juvenile matrinxã can be fed a diet containing 30% CP in both production systems. Furthermore, the results demonstrated that biofloc did not confer a direct benefit to matrinxã juveniles in terms of their feeding, however BFT represented a promising alternative for increasing the survival and improved animal welfare during the rearing phase.