Abstract
Wildfire smoke exposure poses a significant health risk to individuals, particularly in regions prone to wildfires. The effects of wildfire smoke exposure on livestock are less well-known. To address this gap in knowledge, our team has developed a controlled, indoor simulation of wildfire smoke. This study investigates the physiological and behavioral responses of beef heifers to controlled smoke exposure, aiming to evaluate the impact of such exposure on various health and behavioral parameters before, during, and after exposure. In a two-year study, sixteen heifers (Angus × Hereford; 8 months, 230 kg) were individually housed in pens within a completely enclosed barn for 36 days. The study was conducted in three phases: baseline/acclimation (days -7 to -1), where heifers were acclimated to the environment; smoke exposure (days 0 to 7), where heifers were exposed to controlled, simulated wildfire smoke daily for seven consecutive days; and the post-smoke exposure phase (days 8 to 28), where heifers were monitored for three weeks following the smoke exposure. During the smoke exposure phase, smoke was created every afternoon to reduce air quality, which was monitored daily every minute with two air quality monitors using particulate matter 2.5 (PM 2.5) as a major indicator of air quality. Throughout the study, each heifer had ad libitum access to alfalfa hay and water, and feed intake was recorded daily. Health scores were collected daily by trained technicians using the University of Wisconsin Calf Health Scoring System. Blood samples were collected weekly to evaluate acute phase proteins, cytokines, hormones, and hematological markers. Behavior was recorded continuously for the length of the study using four cameras. Preliminary data were analyzed over time using the MIXED procedure of SAS, with each heifer serving as its own control and with year as a random effect. Air quality, measured with PM2.5, changed over time (P ≤ 0.0001), reaching a daily average of 142 mg/m3 during the smoke exposure phase, which was above the EPA safe threshold for human 24-hr exposure (35 mg/m3). Although air quality was reduced during the smoke exposure phase, no changes (P = 0.86) in blood cortisol concentration were observed over time. Blood hematology analysis revealed changes (P ≤ 0.04) in concentration of white blood cells, lymphocytes, and neutrophils. These preliminary data suggest that smoke exposure or poor air quality may impact animal health and have the potential to initiate an immune response in beef cattle. This research was supported by the USDA-NIFA, Award #2023-68008-39173.