Growth, body composition and hepatopancreas morphology of Nile tilapia fingerlings fed crude glycerol as a replacement for maize in diets

This study consisted in determining the best level of replacement of maize by crude glycerol as an energy source for Nile tilapia fingerlings evaluating the growth performance, body composition and hepatopancreas histology. Three hundred Nile tilapia with an average weight of 11.46 ± 2.18 g were placed in 30 plastic aquaria (60 L), in a completely randomized design with six treatments (levels of replacement of maize by crude glycerol at 0, 20, 40, 60, 80 and 100%) and five replications. The feeding regime consisted of three daily feedings ad libitum. An increase (P < 0.05) in crude protein and body moisture, and a decrease in lipids and mineral content in whole body of fish fed with increasing levels of glycerol was observed. Regarding the productive performance hepatosomatic index showed a quadratic effect (P < 0.05) and there was a linear reduction (P < 0.05) in feed conversion with increasing substitution of maize by glycerol. No statistical differences were found (P > 0.05) in the area of hepatocytes and no changes were observed in the morphology of the hepatopancreas. It is possible to replace totally maize by glycerol in pelleted diets for Nile tilapia fingerlings between 10 and 30 g without causing prejudice to the productivity and quality of fish.