Blood parameters and oxidative stress responses in pacu (Piaractus mesopotamicus) reared at different temperatures

The aim of this work was to verify the effect of temperature on blood parameters, reactive oxygen species, and lipid peroxidation of pacu. After acclimation period, 180 healthy juveniles (29.48 ± 2.73 g) were randomly placed in five RAS (12 fish tank−1; 1.68 g L−1 stocking density) and exposed to five treatments (18, 21, 24 [control], 27, and 30 °C—in triplicate) for 45 days. At the end of the experiment, blood samples (n = 9) were used to measure pH, glucose, lactate, hemoglobin, hematocrit, erythrocytes, MCV, MCH, and MCHC. Tissue (liver and muscle) samples (n = 9) were collected for GST, ACAP, TBARS, P-SH, and NP-SH analysis. Blood glucose, hematocrit, and erythrocytes were higher in pacu maintained at 27 and 30 °C. Blood pH was higher at 18 °C and lactate was higher at 18 and 30 °C compared to other treatments. Hemoglobin was lower at 18 and 21 °C and higher at 27 and 30 °C than at 24 °C. GST in the liver was lower at 18 °C than at 24 °C. P-SH in muscle was lowest at 27 and 30 °C, while NP-SH was higher at 21 °C. Sulfhydryl groups (P-SH and NP-SH) in the liver showed a positive linear relationship with the water temperature (R2 = 0.90). TBARS presented a quadratic relationship with the water temperature in the muscle (R2 = 0.85) and liver (R2 = 0.83). In accordance with the hematological parameters, P. mesopotamicus can be reared in the range between 24 and 27 °C. However, 24.09 °C was the optimum temperature as muscle lipid peroxidation was minimum.