Farmers across the world are breeding cows with a mutation that gives them a higher heat tolerance—an advantage that could prove crucial as climate change leads to rising global temperatures. The mutation, called the “slick gene,” is associated with shorter coats and more active sweat glands.
“Hot parts of the world are getting hotter, and parts of the world where heat stress was just an occasional problem are going to find that it’s a more severe problem,” Peter Hansen, an animal scientist at the University of Florida who studies the slick mutation, tells Katherine Rapin of Nexus Media News. “The more the climate is such that cows are exposed to a lot of heat stress, the more important the [slick] gene is going to be.”
Cows thrive in temperatures between 41 degrees and 77 degrees Fahrenheit, per the United States Forest Service—any hotter, and they can experience heat stress. Heat stressed cows produce less milk, are more susceptible to disease and have higher calf death rates. Researchers estimated in a 2015 study that the effects of climate change on U.S. dairy cows have led to annual losses of $670 million in milk production, a figure projected to rise to $2.2 billion by the end of the century.
In Iowa, hundreds of cows died from high heat and humidity in July 2023, the world’s hottest month on record, wrote Tom Polansek for Reuters earlier this month. The heat index hit 117 degrees Fahrenheit on July 28 in Carroll, Iowa, near where farmer Gary Vetter raises cattle.
“They just start dropping and there was nothing you could really do about it,” Vetter told Reuters. “I’ve never seen anything like it.”
To cool overheated cows, farmers usually rely on fans, water misters, cool drinking water and shade. But Rafael López-López, who runs a small dairy farm in Puerto Rico, has been breeding the slick gene into his dairy cows for decades to keep them from overheating, per Nexus Media News.
“I get 1,800 pounds [more] of milk per lactation from these cows, and they reproduce more effectively,” he tells the publication.
Farmers breeding cows with the slick gene in the continental U.S. are still few and far between, but López-López sold one of his bulls to a breeder in Texas, who then has sold the animal’s semen to other U.S. breeders to produce their own heat-resistant cows, per Nexus Media News.
In a small ranch in Whitecroft, British Columbia, in Canada, rancher Joanne Nicklas and her husband have been collaborating with researchers over the past three years to breed beef cows with the slick gene, per CBC News. The gene occurs naturally in at least six different cattle breeds across the world, including Senepol cows in Saint Croix in the U.S. Virgin Islands. The Nicklas family crossbred Senepol and Red Angus cows, and the calves were born last spring. Nicklas has noticed clear differences in the hybrid cows.
“They’ve got a little bit of a pouch on their belly,” she tells CBC News. “They’re up earlier [and] they’re eating more in the heat compared to the other ones.”
John Church, a cattle researcher at Thompson Rivers University in Canada, tells the publication this crossbreed can withstand heat up to 13 degrees Fahrenheit more than Bos indicus, a South Asian cattle breed known for its heat tolerance.
“We believe we’ve created an animal that’s going to be much more climate-resilient and able to handle some of these climate extremes,” he tells CBC News.
Reducing greenhouse gas emissions from raising livestock—especially cattle, which are the leading agricultural source of planet-warming emissions worldwide—is seen as one of the biggest opportunities for addressing climate change.