Growth Performance, Feed Utilisation, Digestive and Metabolic Enzyme Activity, and Liver Morphohistology in Hybrid Tilapia (Oreochromis mossambicus x Oreochromis niloticus) Juveniles Fed with the Inclusion of Chitosan in Their Diet

This study aimed to evaluate the growth performance, feed utilisation, digestive and metabolic enzyme activity, and liver histology in juveniles of hybrid red tilapia (Oreochromis mossambicus x Oreochromis niloticus) fed with the inclusion of chitosan in their diet. Six dietary chitosan levels (0 "control", 10, 20, 30, 40, and 50 g kg(-1)) were used to feed juvenile fish (initial weight 7.50 +/- 0.20 g) that were cultured for eight weeks in 18 tanks at a density of 15 fish/tank. The growth performance presented significant differences (p < 0.05) for weight gain, specific growth rate, feed conversion ratio, hepatosomatic index, and survival rate. The digestive and metabolic enzyme activities were significantly (p < 0.05) influenced by the levels of chitosan in the administered diet. Histologically, no damage was found in the liver; however, morphometrically, a significant difference (p < 0.05) was found in the hepatocyte area and sinusoid area. Vacuolisation of hepatocytes was found in treatments with 40 and 50 g kg(-1) of chitosan in the diet. Treatments with doses of chitosan showed a better response (p < 0.05) compared to the control treatment in most of the different groups of variables analysed. The result of the principal component analysis suggests that a diet containing 40 g kg(-1) of chitosan is optimal for tilapia growth performance.