Effects of wildfire smoke exposure on health parameters and inflammatory responses of beef-on-dairy calves.

The increasing frequency and intensity of wildfires in the western United States have raised concerns about the health and welfare of livestock exposed to wildfire smoke. This study evaluated the physiological, clinical, and immunological responses of beef-on-dairy calves naturally exposed to wildfire smoke. A total of 18 Simmental × Jersey calves approximately 1 month of age were monitored from June to October 2022 in a commercial dairy farm in Vale, Oregon. Air quality was tracked daily, and blood samples and health scoring data were collected monthly before the wildfire (baseline; 3 sampling), weekly for 4 weeks immediately post-wildfire (2 sampling) and late post-wildfire (2 sampling). Samples were analyzed for cortisol, ceruloplasmin, haptoglobin, immunoglobulins A and M, and cytokines IL-1β, IL-6, IL-10, and TNF-α. A local wildfire event (Amelia Road fire; September 8-10) increased fine particulate matter (PM2.5 > 35 µg/m³) for four consecutive days in the study location (44.6 μg/m3). Wildfire smoke exposure induced clear physiological and immune changes. Plasma cortisol concentrations peaked immediately after smoke exposure (10.9 ng/mL; P = 0.007), reflecting an acute stress response. Ceruloplasmin concentrations increased progressively following exposure (P < 0.001), whereas haptoglobin remained unchanged (P = 0.17). Immunoglobulin A and M concentrations increased (P < 0.001) over time, suggesting systemic and mucosal immune activation in response to inhaled particulate matter. Cytokine responses included increased (P ≤ 0.04) IL-1β, IL-6, and IL-10 levels, supporting a transient pro-inflammatory response balanced by anti-inflammatory regulation. No effect was detected for TNF-α (P = 0.56). Clinically, calves remained afebrile but exhibited mild respiratory signs, primarily nasal discharge, immediately following smoke exposure. Collectively, results demonstrate that even short-term exposure to wildfire smoke elicits stress, inflammatory, and immune responses in cattle, despite the absence of obvious clinical disease. These findings highlight wildfire smoke as an underrecognized environmental stressor capable of influencing cattle physiology and immune function. Understanding these subclinical effects is critical to inform management and mitigation strategies aimed at protecting livestock health and productivity during wildfire events.