Desempenho, parâmetros bioquímicos e hematológicos de juvenis de jundiá (Rhamdia quelen), expostos a diferentes níveis de nitrito e cálcio na água

Abstract

The objectives of this study were to determine the effect of different levels of nitrite (NO2 -) associated with calcium (Ca2+) in the water on the performance, biochemical and hematological parameters of jundiá (Rhamdia quelen). One hundred and sixty animals were stored in 16 boxes (n = 10) of 40 liters with constant aeration and kept in a water recirculation system with UV filter for 60 days. The design was completely randomized with 4 treatments and 4 replications in a factorial design with two levels of NO2 - (0,05 e 1,4 mg L-1) x 2 levels of Ca2+ in water (5 e 20 mg L-1). Fish (8.9±0.2 g and 15.0±0.8 cm) were fed with the diet (32% CP and max. 2.0% Ca2+) twice a day at home. Was done daily removal of waste by siphoning, and 80% of the water was replaced by another with nitrite and calcium levels previously set. The nitrite and calcium levels were maintained by the addition of sodium nitrite (NaNO2) and calcium carbonate (CaCO3), respectively. They evaluated: the growth performance, biochemical and hematological parameters for juvenile catfish (Rhamdia quelen). The final survival was not affected by nitrite levels associated with Ca2+. At 30 days, it was observed that there was no change (P>0.05) in weight gain, biomass, specific growth rate and feed conversion between the analyzed treatments. At 60 days, there was an increase (P<0.05) in weight gain, biomass and specific growth rate for animals of the control treatment in relation to the treatment high NO2 - and Ca2+ down, and for treatment low NO2 - and Ca2+ high in relation to the treatment high NO2 - and Ca2+ high. At the end of the experiment, it was found that the feed intake was higher of the treatment low NO2 - and Ca2+ high in relation to the treatment high NO2 - and Ca2+ high. No change (P>0.05) for converting food to end the 60-day trial. No change (P>0.05) in the levels of lactate and glycogen in the liver. The treatment showed control levels (P<0.05) higher protein in the liver compared to fish subjected to high Ca2+ and NO2 - low. Glucose levels in fish liver were higher (P<0.05) in the control treatment in relation to the treatments low NO2 - and Ca2+ high and high NO2 - and Ca2+ down. The levels of lactate and glycogen in muscle showed a lower (P<0.05) in the control treatment in relation to the treatment high NO2 - and Ca2+ down. The protein level in the muscle was lower (P<0.05) in treatment high NO2 - and Ca2+ high in relation to treatment low NO2 - and Ca2+ high and treatment high NO2 - and Ca2+ down. Glucose levels in the muscle had a higher (P<0.05) of the control treatment in relation to the treatment high NO2- and Ca2+ low, and higher of the treatment low NO2- and Ca2+ high in relation to the treatment high NO2- and Ca2+ high. The increase in hardness does not favored animals subjected to high levels of nitrite in relation to the hemoglobin levels. Fish exposed to high NO2 - and Ca2+ high, showed a reduction in this parameter for the processing low NO2 - and Ca2+ high (T2). This result may be an indication that there was blood hemoglobin oxidation in methemoglobin, causing poisoning in fish. Thus, the use of 20 mg L- 1Ca2+ in water has no positive effect in reducing the toxicity of nitrite in relation to performance, biochemical and hematological parameters for juvenile catfishes (Rhamdia quelen).