Abstract

Pirarucu (Arapaima gigas) is a fast-growing, carnivorous species reared commercially in Amazonian countries as Brazil. Lack of a nutritionally balanced and affordable diet is a major constraint in pirarucu aquaculture, and our investigation sought to estimate the dietary protein requirement for this species. Four diets were formulated to contain increasing concentrations of digestible protein (32, 35, 38, and 41%) and fed to triplicate groups of juvenile pirarucu of around 2 kg for 18 weeks. As result, pirarucu showed no differences in feed intake, survival, or fillet yield. However, regression analysis revealed that weight gain (WG) values showed a general increasing trend with increasing dietary digestible protein (DP) level up to 36.7%. In addition, feed conversion rates were also improved with increase in dietary DP up to 36.4%. Fish fed diets containing 32 and 41% had poor feed conversion rates. Thel protein retention rate (PRR) and protein efficiency index (PER) decreased as levels of DP increased. The optimal dietary protein content for juvenile pirarucu between 1.98 and 4 kg of BW is about 36% of digestible protein on diet.

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