Optimization of protein in supplementary feeds for pond raised cyprinids

Labeo rohita, Gibelion catla, Cirrhinus mrigala, Ctenopharyngodon idella and Hypophthalmichthys molitrix were grown together for 365 days in triplicate ponds. Six iso-caloric feeds having varying protein levels i.e. 22, 24, 26, 28, 30 and 32% were prepared and supplemented to fish at 2% fish weight daily. Significantly, higher final average weight (793 ± 197 g) and total length gain (398 ± 40 mm) was recorded for Ctenopharyndodon idella. Net fish yield enhanced as the level of digestible protein (DP) in the supplementary diets increased and plateaued at 28% DP level, thereafter significant reduction (P<0.05) in fish weight increments was experienced at any surplus protein level. Among the supplementary feeds, 28% DP level resulted in maximum net fish yield (4304 ± 33 kg ha^-1 year^-1) and a significantly higher overall nitrogen conversion ratio (NCR) of 1:5.2 ± 0.14. Higher level of DP in supplementary feeds resulted in reduced fish growth.