Effects of ammonia on metabolic parameters and muscle quality of Pacu Piaractus mesopotamicus (Holmberg 1887)
This study aimed to evaluate the effects of exposure to sublethal levels of non-ionized ammonia on blood parameters and on the quality of the pacu muscle (Piaractus mesopotamicus). To carry out this study, 117 juveniles (27.1 ± 5.4 g) were used exposed to three concentrations of non-ionized ammonia 0.5 and 1.0 mg NH3.L-1 and a control 0.0 mg NH3. L-1. The experiment lasted twenty days, ten days of exposure to ammonia, followed by the same recovery period with water in minimum concentrations of ammonia (<0.05). Five collections were made at the beginning of the experiment (9 fish) considered as zero time control and during the experimental period the tissue (muscle) collections for TBARS, fillet for sensory analysis and blood (glucose, lactate and hematocrit), in the first, fifth,tenth and twentieth day (nine fish / collection / treatment). Glucose concentrations were higher in treatments exposed to ammonia than in the control group at all times sampled except in the recovery period. After 10 days of exposure to ammonia, fish exposed to higher concentrations of NH3 showed lower hematocrit values compared to the control. The lactate levels on days 1 and 10 were lower than the control in treatments exposed to ammonia. The hepatosomatic index after 10 days of exposure to ammonia showed lower values when compared to the control. Feed consumption on day 10 was lower in treatments exposed to ammonia compared to control. After the recovery period, the hematological parameters showed no difference indicating the recovery of the fish.The chemical characteristics of the muscle and TBARS values did not differ between treatments. Sensory analysis of fresh fillet after ten days of exposure to ammonia showed lower values in terms of color and overall appearance in the 1.0 mg NH3 treatment. L-1 when compared to the control. Thus, we conclude that exposure to non-ionized ammonia was able to cause changes in hematological parameters and in the sensory analysis of the muscle of pacu juveniles. In addition, the recovery period proved to be sufficient to reestablish normal indexes for hematological parameters and attributes evaluated in the sensory analysis of the pacu muscle.