Influence of pH on hematological, ionic and zootechnical performance parameters in juveniles of pacu Piaractus mesopotamicus (Holmberg 1887)
The pH of the water can be influenced in different ways in the culture systems and its alteration can trigger physiological, biochemical and behavioral changes in the fish, interfering in their development and culture. Thus, the objective of this work was to verify the effects of exposure to different water pH levels on the hematological, ionic and zootechnical performance parameters of juveniles of pacu Piaractus mesopotamicus. For the development of this study, 300 juveniles of P. mesopotamicus (33 ± 1g) were used, which were exposed to four different pH levels (5.5; 6.5; 7.5 and 8.5), in triplicate, for a period of 45 days in a water recirculation system. For hematological analyzes, blood samples were collected on days 1, 2, 5, 15, 30 and 45 after the beginning of the experiment,to quantify the levels of glucose, blood pH, hematocrit and ions in the plasma (Na +, Cl- and K +, only on days 1 and 45). Analyzes of the zootechnical performance parameters (0 and 45 days) of all animals were also performed and the feed intake, the hepatosomatic index and the survival rate during the experiment were verified. The different pH levels in the water did not influence blood glucose levels. Regarding the hematocrit, the values found for all treatments remained within those described for this species (70 to 98 mg.dL-1). The ionic concentrations of Na + and K + were significantly lower in the treatment of pH 8.5 compared to the others, and the zootechnical performance was higher for the treatment exposed to pH 8.5, presenting greater weight and a better specific growth rate,in addition to presenting the highest feed consumption and hepatosomatic index. It is concluded that the pH range of 5.5 to 8.5 can cause changes in hematological indexes. However, pacus raised at pH 8.5 showed better rates of zootechnical performance, thus being the pH value most suitable for the cultivation of pacu juveniles.