Performance of Nile tilapia Oreochromis niloticus raised in cages and fed with different commercial diets

Abstract

The present study evaluated the growth performance of Nile tilapia (Chitralada strain) in cage-culture, considering five commercial diets (I, II, III, IV and V), for finding which feed promoted the highest yield. Groups of eight hundred tilapia fingerlings (48 ± 2.53 g) were stocked in 15 net-cages (4 m³) and were fed  different commercial diets in triplicate for 84 days. Water quality parameters (dissolved oxygen, pH and temperature) were monitored weekly and were considered adequate for tilapia culture. Mean survival rate was satisfactory (80.55 ± 4.52%), and it was not affected by the different diets. The commercial diets I and III promoted higher final weights (454.67 and 491.67 g), daily weight gains (5.20 and 5.67 g fish^-1), and specific growth rates (2.83 and 2.93%) when compared to the others (P < 0.05). Diet III promoted the best apparent protein digestibility coefficient and diet IV promoted the worst one (87.42% versus 76.34%). Diet IV, which presented the highest fiber content, also caused low growth and low body fat deposition (P < 0.05). The best feed conversion rate (1.34) was obtained when fish were fed diet II, which resulted in the lowest production cost kg^-1 (R$ 1.91). The highest production cost (R$ 2.39) was obtained when feeding commercial feed I. Therefore, we conclude that commercial feed II was best suited for tilapia cage-culture because it promoted the best feed conversion rate and the lowest production cost, yielding the best profit.