For dairy cows, where there’s smoke, there’s less milk

Scientists in Idaho are finding that wildfire smoke dampens milk production and coincides with increased risk of disease and even death in dairy cows.

High Country News
3 min readAug 16, 2021


Cows are grazing surrounded by thick smoke from wildfires near Oregon City, Oregon September 12, 2020. Robyn Beck/AFP via Getty Images

Six of Zach Rose’s cows at Rogue Creamery in southern Oregon came down with pneumonia shortly after a bad fire season in 2018, and he thinks the smoke was to blame. “You can see a lot of respiratory issues if they inhale a lot of smoke,” said Rose, the organic dairy’s manager. “We try to keep them indoors obviously as much as possible in those times of really smoky conditions.”

Researchers and farmers are trying to figure out just how harmful wildfire smoke is to dairy cows’ health, and to their own bottom lines. “I bet it does affect milk production,” Rose said. “I’m sure that it certainly can‘t be helpful for it.” This summer, as the Western U.S. battles poor air quality and confronts a hotter, drier future of wildfires exacerbated by climate change, scientists from the University of Idaho are studying dairy cows in the Pacific Northwest to find out more.

Fine particles from wildfire smoke penetrate deep into human lungs, aggravating chronic heart and lung disease and even causing premature death. But smoke’s effects on livestock aren’t well understood, though animals with cardiovascular or respiratory disease are particularly sensitive.

“Humans have the option to move inside and use filtered air,” said Pedram Rezamand, a professor studying animal and veterinary science at the University of Idaho. But dairy cows — though they might spend a portion of their time inside “parlors” being milked — are mostly outdoors, either in a pasture or under open sheds. “We thought, if it’s impacting humans, there’s a good chance it’s impacting animal production and health,” Rezamand said.

Rezamand’s colleague, Amy Skibiel, who studies lactation physiology at the University of Idaho, is spearheading a project to investigate the links between wildfire smoke exposure and cattle health. The research team first collected five years of data on cow disease and deaths from two farms in Idaho and Washington, then looked for patterns that lined up with archived weather and air-quality data. They also recorded physiological measurements, like rectal temperatures and body weight, along with milk production stats, from 25 cows at the campus dairy farm over a three-month period that included a major weeklong smoke event.

Preliminary results show higher incidence of disease — especially mastitis, an udder infection — and increased risk of mortality among calves when wildfires elevated the level of fine particulate matter, or PM 2.5, in the air. Researchers also found changes in immune cells and signs of inflammation. “This raises more questions,” said Skibiel. The connection between inhaling wildfire smoke and irritated udders is intriguing, Skibiel said: “It’s certainly worth following up on.”

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