Microscopic alterations and adaptation in the lungs of the Japanese quail exposed to acute or chronic heat stress

Global warming causes heat stress, a significant bioclimatic factor affecting poultry welfare. The effects of heat stress on the morphology of the Japanese quail lungs were investigated in this study. A total of 16 adult Japanese quail were randomly distributed into four groups: a control group (CT), acute heat stress (AH), chronic heat stress with 7 days (CH1) and chronic heat stress with 28 days exposure (CH2). The CT group were maintained at 25 °C temperature, the AH group were exposed to 38 °C temperature for 24 h, and the CH groups were exposed to 35 °C for seven and 28 days. At the end of exposure, the birds were euthanised, and lung tissues were collected and processed for microscopy. Tissue sections were stained using H&E stain, Gomori’s stain and immunofluorescence labelling. This study showed no significant difference in body weight, cloacal temperature, respiratory rate and lung parameters in heat-stressed groups compared with the control group. However, microscopic analyses revealed blood congestion, leakage of blood into the airway, inflammatory response and tissue breakage in the heat-stressed groups. Heat stress harmed the lungs of the Japanese quail based on duration and intensity. The negative impact could cause instant mortality, but if the quail survives the initial impact, it can adapt to the heat stress with long-term consequences on its performance.