Effects of dietary supplementation with Hesperozygis ringens essential oil on hematological and biochemical parameters of juvenile Piaractus brachypomus under different temperature conditions

Environmental temperature directly influences fish physiology and may alter hematological and metabolic responses. In aquaculture, phytogenic additives such as essential oils have been investigated as dietary supplements capable of improving physiological stability under stressful conditions. This study evaluated the effects of dietary supplementation with Hesperozygis ringens essential oil (HREO) on the hematological and biochemical parameters of juvenile Piaractus brachypomus reared at different water temperatures. A total of 448 juveniles (9.38 ± 0.07 g) were distributed in recirculating aquaculture systems under a completely randomized 2 × 4 factorial design, consisting of two temperatures (27 and 31 °C) and four dietary HREO inclusion levels (0.00, 0.75, 1.00, and 2.00 g kg⁻¹ feed) for 30 days. At the end of the experimental period, blood samples were collected for hematological and biochemical analyses, including hematocrit, hemoglobin, total plasma protein, glucose, triglycerides, cholesterol, alanine aminotransferase (ALT), and aspartate aminotransferase (AST). The main compound identified in HREO was pulegone (93.72%). Data were analyzed using two-way ANOVA followed by Tukey’s test (p < 0.05). Hematocrit, total plasma protein, and glucose were affected only by temperature, with higher values observed at 31 °C (p < 0.05). Triglycerides and AST levels were higher in fish reared at 27 °C (p < 0.05). Hemoglobin and cholesterol were not influenced by temperature, dietary HREO supplementation, or their interaction (p > 0.05). ALT showed a significant interaction between temperature and HREO inclusion levels, with higher values observed in fish fed 2.00 g kg⁻¹ HREO at 27 °C. Intermediate HREO inclusion levels (0.75 and 1.00 g kg⁻¹) promoted more balanced physiological responses. Water temperature was the main factor influencing hematological and biochemical responses in juvenile P. brachypomus. Dietary HREO supplementation did not negatively affect physiological parameters, and intermediate inclusion levels may contribute to improved metabolic stability under different thermal conditions. Financial support: CAPES and CNPq