Wildfire smoke has well established detrimental links to human health. It increases respiratory issues, is linked to dementia, and can even be fatal among the most vulnerable groups.

But scientists are still working to uncover how wildfire smoke affects other living beings, in both the short and long term. Researchers at Oregon State University took another step to uncover that mystery by studying one of the state’s most important agricultural commodities: cattle.

The researchers recently published their findings in the Journal of Animal Science, showing that wildfire smoke often causes invisible yet meaningful health issues in beef-on-dairy cattle, which contribute around $791.5 million annually to the state’s economy. The study analyzed 18 beef-on-dairy calves on a commercial dairy near Vale in 2022 and tracked their health before and after smoke from the Amelia Road fire affected local air quality for four days.

The calves did not develop any obvious diseases after the smoke exposure, but blood tests told a more subtle story, according to researchers Juliana Ranches and Jenifer Cruickshank.

“After smoke exposure, calves showed higher cortisol, a sign of acute stress,” the researchers said in a university press release. “They also showed changes in inflammatory markers, immunoglobulins and cytokines, indicating that smoke exposure activated immune and inflammatory responses even without severe outward illness.”

The immune and stress responses triggered by wildfire smoke are at risk of causing future health issues, such as increased susceptibility to secondary respiratory infections or reductions in growth or productivity, according to the study. The findings become more concerning due to their similarity to bovine respiratory disease symptoms, which makes potential wildfire smoke-caused symptoms even harder to diagnose.

The study’s findings show just how much wildfire smoke can act as an environmental stressor on cattle’s physiology and immune function, the researchers said. The “subclinical” effects are critical to informing ranchers’ future management and mitigation strategies for protecting their livestock.

Click here to read the full study.