Utilização de fitoterápicos como redutores de estresse no transporte de tambaqui (Colossoma macropomum)

Abstract

Transport is an important procedure in fish farming, in which substances such as salts and / or anesthetics are added to relieve stress and increase fish densities for optimization of the process. In the present study, the use of essential oils of melaleuca and clove or salt added in the transport water of tambaquis in a closed system was evaluated. For that, three experiments were carried out. In the first, the effect of different concentrations on the survival and water quality of tambaqui during the transport simulation was evaluated and the most appropriate concentration was determined for this procedure. In the second and third experiments, the efficacy of the concentration determined in the previous experiment compared to the salt during transport was evaluated using the following indicators: plasma ions, haematological, histological and metabolic parameters. The following concentrations were added to the water in the first experiment: 2.78, 5.56, 8.34, 11.12 mg L-1 melaleuca oil; 2.43, 4.86, 7.3, 9.12 mg L-1 clove oil, 2.60, 5.20, 7.80, 10.40 mg L-1 of mixed (the two combined oils 1 :1); 0.8% salt + melaleuca oil (5.20 mg L-1); clove oil (4.86 mg L-1) + 0.8% salt, mixed (5.20 mg L-1) + 0.8% salt. Each concentration constituted a treatment with 5 replicates. The control group did not have the addition of additives. The second and third experiments had duration of 15 h and 36 h of transport, respectively. The addition of the mixed concentration of 10.40 mg L-1 of melaleuca oil and clove was the MEUG treatment; 0.8% salt added constituted the SAL treatment. A group of fish not submitted to transport constitutes the basal group. In the first experiment, treatments at 11.12, 9.20 and 10.40 mg L-1 of melaleuca, clove and mixed oil, respectively, provided the highest transport times. The total ammonia concentration increased with the transport period, being lower than the control in the oil treatments of melaleuca at 11.20 and in the mixed at 10.40 mg L-1. The dissolved oxygen remained at higher values at these concentrations. Survival after recovery was greater in mixed treatment at 10.40 mg L-1. This concentration proved to be more appropriate for long-term transport (up to 48 h). The results obtained in the second and third experiments showed that levels of cortisol, glucose and plasma lactate increased after transport compared to values before transport. The glycemic values of the MEUG treatment were lower than that of the SAL treatment, regardless of the transport time. The same was true for lactate, only in the 15 h experiment. Hepatic glycogen levels were higher in the MEUG treatment. There were no changes in the ions (sodium, chloride, potassium) regardless of the treatment and the transport time. The hemoglobin concentration increased in the SAL treatment, after the transport of 15 h and 36 h. The gills had no deleterious morphophysiological changes. Except for hepatic glycogen in SAL treatment, all parameters were like baseline after recovery for 96 h. The indicators showed primary and secondary responses to stress, showing more favorable results for the transport of tambaquis for 15 and 36 h with the use of essential oils combined with melaleuca and clove at 10.4 mg L-1 as sedatives.