Effect of Feeding Rate on Survival, Zootechnical Performance of Tilapia Oreochromis niloticus (Linnaeus, 1758) Brazil Strain Larvae Fed on 17-α-methyltestosterone Treated Feed

This study was conducted to evaluate the feeding levels on survival, growth performance and feed utilization in the Brazil strain of Nile tilapia Oreochromis niloticus. Four (4) batches of larvae with mean initial weight 0.012 ± 0.005 g and mean initial total length 9 ± 0.003 mm were formed in triplicate, three per feeding rate. The rationing rates according to fry biomass applied in this trial were: batch 1: 50, 40, 30 and 25%, batch 2: 40, 30, 25 and 20%, batch 3: 30, 25, 20 and 18% and batch 4: 25, 20, 18 and 15% of biomass. The different feeding rates were tested during the 1st, 2nd, 3rd and 4th week of larval rearing respectively. The fish were all fed a commercial feed (48% protein) distributed manually at a frequency of 5 meals per day. After 28 days of rearing, the results show that apart from the survival rate, the other parameters such as final average weight, daily growth and food consumption index were affected by the different rationing rates tested. The larvae of batch 2 rationed at 40, 30, 25 and 20 % of their biomass during the 1st, 2nd, 3rd and 4th week of rearing respectively recorded significantly higher growth parameters (MWF: 1.092±0.027 g and DG: 0.038±0.000 g) and a more interesting food converion ratio (0.88 ) than the other batches of fry. From this study, it is concluded that an optimal feeding rate of 40, 30, 25 and 20% of the larval biomass during the 1st, 2nd, 3rd and 4th week of rearing, respectively, should be applied in order to avoid either wastage or underfeeding of the subjects during hormone treatment with 17 α-methyltestosterone.