Wildfires Are Bad for Your Butter, Study Shows

Researchers found a significant decrease in milk production when dairy cows were exposed to smoke.

Last fall, when wildfires raged across parts of Oregon, more than two dozen dairy farms had to figure out how to milk and feed their cattle despite the dangerous conditions and poor air quality. One farmer in the Willamette Valley said that the heavy smoke meant that his cows had to be put in trailers, which both stressed them out and upended their daily routines.

Wildfires have unfortunately become a more regular occurrence in the western United States, and researchers are working to determine what other effects that smoke inhalation can have on dairy cattle, including what impact it can have on their milk production. Ashly Anderson, a graduate student at the University of Idaho College of Agricultural and Life Sciences, along with assistant professors Pedram Rezamand and Amy Skibiel took blood samples from 28 purebred Holstein cows and their calves last summer, to study whether certain immune markers changed before, during, or after the cows were exposed to a week of heavy smoke from the Snake River Complex fires.

Cows lined up look away from a wildfire
Weed, California USA - June 29, 2021: The Lava Fire burns on the northwest side of Mount Shasta in Siskiyou County, California. Cows lined up look away from the wildfire. Trevor Bexon / Shutterstock

"Due to climate change and global conditions, we're going to be seeing a lot more wildfires and because of that there are going to be a lot more people and animals exposed to wildfires," Anderson said. "Being able to tell what kind of effects there are and how we might be affected in the future is very important."

According to High Country News, the University of Idaho researchers also analyzed five years of data from two dairy farms in Idaho and Washington state, along with the weather patterns and air quality from that same time span. In addition to the blood samples, measurements, and metabolic data, they also took note of the Holsteins' milk production for a three-month period last year, including during a "major weeklong smoke event."

Their data seem to show a "significant" decrease in milk production; the cows studied produced three pounds of milk — around one-third of a gallon — less every day. (High Country News reports that the average dairy cow in the United States produces 65 pounds of milk per day.) In addition to giving less milk, the cattle studied were more prone to udder infections and showed signs of inflammation. "This raises more questions," Skibiel told the outlet. "The connection between inhaling wildfire smoke and irritated udders is intriguing. It's certainly worth following up on."

Interestingly, an Oregon dairy farm whose Guernsey cows were not included in the study, said that she saw an increase in the number of calves that developed pneumonia in the weeks that followed the wildfires, and those cases "seemed to set in harder and faster than usual." And another Idaho rancher told the Idaho Capital Sun that the fires affected his pastures because wild game are coming onto his land to find food — and that, in turn, affects his cattle. Due to the decrease in "high-quality grass," he said his herd may have lower pregnancy rates this fall, and lower birth rates next spring.

"People are starting to pay attention and starting to realize wildfire issues are going to increase for the foreseeable future," Skibiel said. "I'm really hoping within the next year we have a better sense of the big picture."

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