Different vitamin levels C in the ration on the ectoparasitas occurrence, survival and total biomassa in Nile tilápia fingerlings (<em>O. niloticus</em> L.)

Abstract

Different vitamin levels C in the ration on the ectoparasitas occurrence, survival and total biomass in fingerlings of Nile tilápia Oreochromis. Niloticus L. (Perciformes, Cichlidae) were evaluated after sexual reversion, for 57 days. Fingerlings began the experiment with approximately 0,30g and 24mm and were submitted to four diets with 300-mg (T1), 600-mg (T2), and 900mg-(T3) e 1200-mg (T4) of vitamin C/kg of ration. In the beginning the ectoparasites occurrence was of 100%, 38,0% of Trichodina and 62,0% of mixed infection (Trichodina and monogenetics). At the end, there was not significant difference for total occurrence, for Trichodina and mixed infection. Considering the occurrence of the monogeneas there were significant differences between T1 and the others. In relation to the schedules of collection, a significant difference was found in the occurrence among the schedule of the 15:00 compared to the other schedules. No significant differences were observed in relation to weigh, total and standard medium length, biomass and survival, though. Results indicated that it is unnecessary to use vitamin C in superior levels to the 300-ration mg/Kg, enough to reach the tilápias fingerlings' nutritional needs, bred in controlled system.