Optimization of dietary protein level for good aquaculture practice based carp fattening in ponds under drought prone area of Bangladesh

Abstract

Good aquaculture practice (GAP) based carp fattening is a potential technique to obtain higher and safe fish production within shorter period in ponds of drought prone area. Sustainability of this technique, however, is constrained by high feed cost and poor water quality. Therefore, as an overcoming effort, three diets (protein content of 20%, 25% and 30%) under three different treatments (T1, T2 and T3) were tested during January-June, 2020 in fattening ponds of carps (Catla, Gibelion catla; silver carp, Hypophthalmichthys molitrix; rohu, Labeo rohita; mrigal, Cirrhinus cirrhosis; and carpio, Cyprinus carpio var. specularis) under Rajshahi district, Bangladesh. Variation in protein level had no significant effect on environmental parameters of pond water. Combined fish yield was found to vary significantly (P<0.05) among the treatments, while feed conversion ratio did not vary significantly. Although second degree polynomial regression analysis identified 28.50% dietary protein for optimal growth of carps but no significant difference between T2 and T3 was found for the total fish yield. However, significantly (P<0.05) highest cost-benefit ratio obtained with the diet containing 25% protein suggested this protein level in diet was profitable for carp fattening in pond.