Eucalyptus globulus essential oil alleviates cold-induced ascites and physiological disturbances in broiler chickens

This study evaluated the efficacy of Eucalyptus globulus essential oil (EEO) supplementation in attenuating ascites incidence and physiological disturbances in broiler chickens exposed to a cold-induced pulmonary hypertension syndrome model. A total of 720 one-day-old male Ross 308 chicks were randomly assigned to six dietary treatments, each with six replicates of 20 birds. The thermoneutral control group received a basal diet under standard conditions (32°C on day 1, gradually reduced to 23°C by day 20 and maintained until day 42; relative humidity [RH] 50-60 %), whereas the remaining five groups were exposed to cold stress (temperature reduced by 4°C/day from day 11 until reaching 15°C, then maintained at 10-15°C until day 42, RH 55-65 %) to induce ascites, and were fed the basal diet supplemented with 0, 500, 1000, 1500, or 2000 mg/kg EEO. Cold stress decreased body weight gain and feed intake and increased ascites-related mortality (P < 0.05). It also elevated erythrocyte count, hemoglobin concentration, and hematocrit, while reducing pO₂ and O₂ saturation and inducing right ventricular hypertrophy (P < 0.05). In contrast, inclusion of EEO in the diet linearly improved body weight gain, partially restored hematological parameters, and favorably modulated blood gas values compared with the unsupplemented cold-stressed group (P < 0.05). Cold stress also suppressed superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities in plasma and heart tissue, increased malondialdehyde (MDA) concentrations, and lowered plasma nitric oxide (NO) levels (P < 0.05). Dietary supplementation with EEO linearly increased SOD and GPx activities and plasma NO concentrations, while reducing MDA content (P < 0.05). Although EEO supplementation improved growth performance and physiological responses in cold-stressed broilers, values did not fully return to thermoneutral levels. Overall, these findings highlight the potential of EEO as a functional dietary additive to mitigate the adverse effects of cold-induced ascites and oxidative stress in broiler chickens.