Effects of Eucalyptus globulus essential oil on alleviating respiratory tract injury and modulating lung microbiota in heat-stressed broilers

JI Zhenzhen; LIU Tongshuai; LI Xuanyang; LI Fangxu; XING Xican; CHENG Pu

doi:10.13557/j.cnki.issn1002-2813.2025.17.007

Abstract：The experiment aimed to investigate the effects of Eucalyptus globulus essential oil(EGO)on the alleviating respiratory tract injury and modulating lung microbiota in heat-stressed broilers.A total of 270 healthy male Kebao broilers with similar body weight at 21 days of age were selected and randomly divided into six groups.They were respectively the control group(CON group),the heat stress group(HS group),the positive control group(PC group),and the low(100 mg/kg),medium(200 mg/kg),and high(300 mg/kg)dose EGO groups(HS+EGO-L group,HS+EGO-M group,and HS+EGO-H group),with three replicates per group,and 15 chickens per replicate.The CON and HS groups were fed with the basal diet.The EGO group was proportionally supplemented with EGO in the basal diet,and the PC group was supplemented with 200 mg/kg doxycycline in the basal diet.The ambient temperature of the CON group was set at(24±1)℃ throughout the day,while the other groups were subjected to heat stress treatment.The ambient temperature was set at(32±1)℃ from 9:00 to 17:00 each day,and at(24±1)℃ for the rest of the time.The formal test period was 21 days.The results showed that compared with the CON group,the HS group exhibited significantly downregulated mRNA expression of interleukin-10(IL-10)and Claudin-1 in the lung tissue of broiler chickens(P＜0.05),but significantly upregulated zonula occludens-1(ZO-1)and Occludin mRNA expression(P＜0.05).Compared with the HS group,dietary EGO and doxycycline significantly upregulated IL-10 mRNA expression in the lung tissue of broiler chickens(P＜0.05)and significantly downregulated interferon-y(IFN-γ)and ZO-1 mRNA expression(P＜0.05).Claudin-1 mRNA expression was significantly upregulated in HS+EGO-L and HS+EGO-H groups(P＜0.05),while Occludin mRNA expression was significantly downregulated in HS+EGO-M,HS+EGO-H,and PC groups(P＜0.05).Additionally,EGO altered lung microbiota diversity with compositional variations across groups.The study indicates that adding EGO to feed can improve the morphology and structure of respiratory tissues in heat stressed broiler chickens,regulate cytokine secretion,mitigate inflammation,enhance pulmonary barrier function,and modulate lung microbiota to maintain respiratory health.The better effect is achieved when the additive dosage is 300 mg/kg.