Effects of different protein levels on growth indices of common carp (Cyprinus carpio) fingerling in the intensive culture system

The present study examined the effects of different protein concentrations  on growth of juvenile common carp kept in 15 fiberglass ponds (0.5 × 2 × 2 m) under intensive culture system involving 5 treatments and 3 replications, based on the following raw protein contents  (24.22, 26.15, 28.32, 30.31, 33.29%) included in the fish diet for a period of 60 days and with a water temperature ranging 22-31oC, and dissolve oxygen level of 5.1-7.3 mg/L to determine diet formulation ensuring an optimum growth performance. Each rearing pond was introduced with 250 pieces of juvenile fish (4 ± 0.66 g) amounting to an average of 1 kg fish biomass. The results indicated that juveniles receiving protein levels of 28.32% and 26.15% had the highest body weight, specific growth rate, weight gain percentage and protein yields (p≤0.05). In addition, the feed conversion ratio related to these two diets showed significant decline (p≤0.05). The condition factor and survival rate remained the same across all treatments (p≥0.05). The study revealed that the protein increment ratio of up to 28.15% in the diet contributed to the increased growth indices among juvenile common carp and concentrations beyond that did not lead to any effective increase in fish growth.