According to Jenifer Cruickshank, an assistant professor in the College of Agricultural Sciences at Oregon State University, wildfires are becoming more frequent and severe. In 2022, there were 68,988 wildfires in the U.S. burning 183 million acres. It’s predicted that by the next century there will be a 74% – 118% increase in the area burned by wildfires. This is, in part, attributable to climate change.
“One might have thought this was mostly a Western states problem in terms of smoke coming from wildfires. Folks were disabused of that notion earlier this summer with the wildfires that were burning in eastern Canada, and the smoke was drifting hundreds and hundreds of miles to the south,” Cruickshank said.
Currently, there’s not a lot of published research about the impacts of wildfire smoke on livestock and agricultural crops. Cruickshank and her colleagues have funding lined up for a number of research projects. In the meantime, they’re eager to share what they know.
What’s in wildfire smoke?
Wildfire smoke consists of gases – carbon monoxide and dioxide, nitrogen oxides, volatile organic compounds and hydrocarbons – and particulate matter (PM), comprising liquid and solid particles suspended in air.
PM is divided into two categories – particles between 2.5 and 10 microns in diameter (PM 10) and particles that are less than 2.5 microns (PM 2.5). For some context, human hair is 50 to 70 microns wide. PM 10 includes dust, pollen and mold, and these larger particles tend to get trapped in the upper respiratory tract.
PM 2.5, on the other hand, is tiny. “What this means is that when we inhale, when cows inhale, when anyone with lungs inhales, these particles can deposit deep into the airways,” Cruickshank said. “These are the ones that we’re really worried about.”
Researchers don’t yet understand the differences in PM depending on which type of material is burning. For example, what is the difference in PM in burning grasslands versus burning forests? To research this, Cruickshank and her colleagues are applying specialized silicone ear tags to calves grazing on rangeland in eastern Oregon. The tags absorb what is in the environment so the team can understand what the calves were exposed to under specific wildfire conditions.
What impact does wildfire smoke have on livestock?
Cruickshank summarized several studies that showed the impacts of PM 10 on livestock. PM 10 was associated with increased cattle mortality, heightened pneumonia risk in beef and dairy calves and an increased risk of lung lesions in pigs. Lactating ewes in moderately ventilated barns having lower PM exposure had higher milk yields. And increased ambient PM and increased temperature humidity index resulted in lower milk yield and higher somatic cell count in dairy cattle.
“There’s evidence from multiple species that particulate matter, in general, is not healthy,” Cruickshank said.
In terms of PM 2.5 exposure, Cruickshank cited a study by her colleague at the University of Idaho. In this study of dairy cattle exposed to wildfire smoke, researcher saw a decrease in milk yield of 2.7 to 2.9 lbs./day. The protein percentage also decreased by 0.1% to 0.3%. These data were independent of temperature and humidity.
In the same study, researchers conducted blood sampling of the dairy cattle exposed to wildfire smoke and found there was an increase in some white blood cells and a decrease in red blood cells and neutrophils. Metabolic changes included a decrease in blood urea nitrogen and an increase in non-esterified fatty acids.
In another study, researchers found that calves exposed to wildfire smoke suffered an increase in eye discharge and coughing, a higher incidence of calf mortality and a decrease in white blood cells.
Cruickshank noted that there is a lag effect after exposure to wildfire smoke. She said, “It isn’t just the day that is smoky where we see the reduction in milk yield. Even if it is really, really smoky for two days, and the smoke clears on day three, four and five. They measured up to seven days following smoke exposure, and there was still a depression in milk yield.”
How can producers protect their livestock from wildfire smoke?
First, producers should reduce livestock activity and exercise. The idea is that the animals will breathe less, and therefore there will be less PM entering the lungs.
Since wildfire smoke tends to occur under hot and dry conditions, Cruickshank said it’s important to reduce additional stressors such as heat by using shade, fans and/or misters. Water can also be used to help reduce dust coming from feed or facilities.
Similarly, stressors such as weaning, changing groups, vaccinations and transporting should be postponed until the air quality improves.
She also suggested keeping clean, fresh water available at all times because well-hydrated respiratory tracts are less prone to irritation.
Cruickshank acknowledged that these suggestions are basic. Through research, she and her colleagues hope to develop a more detailed list of advisory actions. Future research projects include investigating if it’s possible to use filtration in free-stall barns to remove PM 2.5.
“Can we pull a meaningful amount of particulate matter out of the air? Is it practical to try to do that, or is it a lost cause?” she asked. They also plan to study the effects of wildfire smoke on crop quality.
Finally, given the increased risk of wildfires in the future, producers should develop a fire contingency plan. “With the way the climate is changing and things are getting drier and fire seasons are getting longer, the potential for fire becomes more possible,” Cruickshank said.
If a producer plans to evacuate livestock, they should develop a strategy for where the herd will move and how it will be transported. It’s also important for producers to stay informed with up-to-date weather conditions. If livestock must be left behind, Cruickshank suggested making water available and leaving gates open to maximize freedom of movement.
For more information about the impact of wildfires on livestock health visit livestockwildfirehub.org.
by Sonja Heyck-Merlin