Growth response of juvenile Barbodes altus fed isocaloric diets with variable protein levels

An experiment was carried out to determine the dietary protein requirement of the cyprinid fish Barbodes altus cultured under controlled conditions. Seven approximately isoenergetic purified diets were formulated with protein levels ranging from 20 to 50%, in increments of 5%, and fed to young B. altus (0.8 +/- 0.012 g body weight and 4.27 +/- 0.10 cm total length). The feeding trial was conducted for 10 weeks with triplicate groups in each treatment and the fish were fed at 5% body weight daily. Weight gain was proportional to protein levels up to an incorporation rate of 40%; beyond this level, it was significantly (P < 0.05) reduced at 50% dietary protein. Growth response data calculated by quadratic regression showed that the minimum dietary protein level required for maximum growth was 41.7%. Feed efficiency increased with increasing protein levels in the diet up to 40% protein, then significantly (P < 0.05) decreased for fish fed the diets containing 45 and 50% protein. The protein efficiency ratio decreased with increasing dietary protein levels. However, carcass protein, fat and ash contents were not significantly (P > 0.05) affected by various dietary protein levels. (C) 1997 Published by Elsevier Science B.V.