Nutrient digestibility and growth of hybrid tilapia, Oreochromis niloticus × O. aureus, as influenced by agar supplementation at two dietary protein levels

Abstract

An experiment was conducted to study the influence of agar on nutrient digestibility and growth of fingerling tilapia at two dietary protein levels. Average initial body weight of the fish was 1.04±0.04 g. Fish were fed 3% of their body weight/day. Significantly (P<0.05) lower body weight gain, feed efficiency ratio (FER), protein efficiency ratio (PER) and energy retention were observed in fish fed the agar diet at 35% dietary protein level. Higher body weight gain, FER and energy retention and lower PER were observed in fish fed 35% dietary protein either with or without agar supplementation than those fed a 24% protein diet. Lower carbohydrate and dry matter digestibility values were observed in fish fed the agar diet at both 35% and 24% protein levels. Higher carbohydrate digestibility was observed in fish fed a 24% protein diet with and without agar than those fed a 35% protein diet. These data suggest that the inclusion of 10% agar in the diet reduced growth of tilapia when dietary protein level was 35%. However, growth retardation of the fish was not observed by agar supplementation when the dietary protein level was low (24%).