Dietary requirement of myo-inositol for Nile tilapia (Oreochromis niloticus) fingerlings fed practical diet

Present research work was designed to determine the dietary requirement of myo-inositol for Nile tilapia (Oreochromis niloticus) fingerlings fed practical diet. Five semi-purified diets namely D1, D2, D3, D4 and D5 were formulated by supplementing myo-inositol at the graded levels of 0, 100, 200, 400 and 800 mg/kg diet respectively. Duplicate tanks were allotted for each experimental diet and each tank was stocked with 15 fingerlings. Water quality parameters i.e. temperature, dissolved oxygen and pH were monitored throughout the feeding trial. Growth and survival rate were observed every week during the whole experimental period. At the end of the trial, 10 fingerlings were sacrificed from each replicate to analyze the thiobarbituric acid reactive substances (TBARS), anti-oxidant enzymes and fatty acid composition of gills tissues. Data was subjected to one-way analysis of variance (ANOVA) under completely randomized design (CRD). The results indicated significantly improved growth in Nile tilapia fingerlings in response to myo-inositol supplementation. Based on weight gain (%), the quadratic regression analysis indicated that Nile tilapia fingerlings required 457.78 mg/kg myo-inositol for normal growth. The activities of antioxidant enzymes (SOD, CAT, GPx) and TBARS content were also enhanced in fishes fed myo-inositol added diets than the control group. Also, a significant increase in palmitic acid (16:0 n-0), arachidonic acid (20:4 n-6) and ARA/EPA ratio was recorded in gills tissue in response to myo-inositol supplementation. Inclusion of myo-inositol significantly decreased the hepatosomatic index while it did not affect the viscerosomatic index in Nile tilapia fingerlings. In conclusion, addition of myo-inositol in the diets improved the fish growth and activities of antioxidant enzymes in gills of Nile tilapia fingerlings.