Protein to energy ratios and cost, performance, and ammonia excretion in juvenile jundiá (Rhamdia quelen), South American catfish

ABSTRACT: The determination of nutritional requirements, based on diets administered in practice, considers physiological specificities and sustainability are essential to the development suitable aquaculture technologies for novel fish species. growth jundia (Rhamdia quelen Quoy Gaimard) juveniles (31.54 ± 4.92 g) fed five comprising increasing levels digestible protein (DP: 24, 29, 34, 39, 44 %) energy (DE: 12.13, 13.39, 13.81, 14.64, 15.06 MJ kg−1) with DP:DE ratios: 20, 22, 25, 27, 29 g MJ−1, respectively, was evaluated. Each diet three groups 25 75 days. Regression analysis showed that different ratios affected both economic performance as well excretion total ammonia nitrogen. Fish between 22 27 MJ−1 achieved a higher daily weight gain, superior apparent net utilization, feed conversion rates, lower costs. For economically viable environmentally friendly farming initial grow–out stage (30 80 average weight), best ratio (34.05 % DP 13.81 kg−1 DE).