Efeitos da suplementação com vitamina C em diferentes níveis de arraçoamento no cultivo de Tilápia do Nilo (Oreochromis niloticos) em esgoto doméstico tratado

Abstract

The effect of supplementation was evaluated with vitamin C at different feeding rates in the cultivation of Nile tilapia (Oreohromis niloticus) on effluent of wastewater plant. For this, nine tanks were used with 50 m³ volume, which there were supplied with treated domestic sewage from a system of stabilization ponds in three treatments: T 01 - 50% of the ration (fish food) provided by the manufacturer supplemented with Vitamin C; T 02 - 25% of the ration (fish food) provided by the manufacturer supplemented with Vitamin C and T 03 - 50% of the ration (fish food) provided by the manufacturer without supplemental feeding. The fishponds were populated with fingerlings of Nile tilapia, sexually reverted to males, with average weight of 1.5 g and stocking density of three fingerlingsm-³. The quality of reuse water tanks and water tributary to the cultivation of the experimental treatments by physico-chemical and biological were evaluated. Furthermore, the microbiological quality of three tissues was verified using the standards proposed by ANVISA Resolution No. 12 of 2001 to measure food security of the practice of using treated effluents in aquaculture. To check the viability of economic activity, an economic analysis simplified was realized of the tested treatments. The duration of the state of rigor mortis of fish produced in domestic sewage was tested with and without effluent treatment, by checking the effect of the way to slaughter by hypothermia and use of eugenol. The data collected were submitted to ANOVA and Tukey's test for significance of 5.0% (p ≤ 0.05). The main parameters observed and the results obtained for the treatments 01, 02 and 03, respectively, were: daily growth, 0.16±0.02a, 0.16±0.01a and 0.17±0.02a cmday-1, daily weight gain, 1.44±0.29a, 1.27±0.16a and 1.24±0.16a gday-1; productivity, 43.24 ± 8.76a, 37.66 ± 4.65a and 37.20 ± 4.85a kgha-1day-1; survival rate, 100%, 98.67% and 100%. The water-quality parameters evaluated were demonstrated feasibility for the cultivation of tilapia using treated sewage. The microbiological quality of tilapia produced was within the standards established by ANVISA, enhancing food security in the use of domestic sewage in fish culture, following the experimental conditions used in this investigation. Between all the tested treatments, the best economic outcome was shown for the treatment 2, because it had the highest partial net income, parameter that indicates the profit of an activity. This occurred primarily by this treatment use half the amount of fish food used in other treatments. To increase the consistency of the results of this research, the tilapia produced were shown a complete resolution of rigor mortis takes longer when compared with results from other researchers. The results of the index of rigor mortis observed were shown that the culture medium rich in natural food increased the energy levels of the fish, making the longer the period of rigor fish, preserving its quality and freshness, making it the longest shelf life and time to completion of processing of fish produced.