VITAMIN-D REQUIREMENTS OF JUVENILE HYBRID TILAPIA OREOCHROMIS-NILOTICUS X OREOCHROMIS-AUREUS

A feeding trial was conducted to estimate the optimum vitamin D requirement in the diet for juvenile hybrid tilapia Oreochromis niloticus x O. aureus. Eight vitamin D levels, ranging from 0 to 2,100 IU/kg diet at a 300 IU increment were fed for 16 weeks to triplicate groups of tilapia weighing 0.78 g in a recirculated double filtered rearing system. Results indicated that fish fed with diets lacking supplementary vitamin D had poor growth and feed conversion ratio (FCR), and low hemoglobin, hepatosomatic index values, and plasma alkaline phosphatase activity. Plasma calcium and phosphorus concentration were similar in all the dietary groups. Weight gain analyzed by broken line regression indicated the vitamin D requirement for maximum growth in tilapia to be 374.8 IU/kg.