GAINESVILLE, Fla. – Beating the heat is a big deal for cattle. At temperatures as low as 72 degrees Fahrenheit with 50 percent humidity, cattle can experience heat stress. Heat-stressed cattle intake less feed, impacting productivity. In the U.S., these decreases in productivity result in a loss of $369 million annually.

Raluca Mateescu, a professor in the Department of Animal Science at the University of Florida, and her research team are interested in improving animal resistance to heat stress while increasing production efficiency. Her latest work investigated the genetic control of sweat gland characteristics in beef cattle.

Mateescu said beef cattle dissipate about 85 percent of their internal heat through sweating. Cattle sweat when their heat load increases due to high temperatures and humidity. Cattle sweat glands are less effective than other mammals, and for the sweat to be cooling, the animal must exert a lot of energy to evaporate the sweat. High-producing cows eat more and generate more heat, making them more likely to experience heat stress at lower temperatures.

Best practices for managing heat stress in cattle include providing shade, ventilation, sprinklers and misters, and plenty of drinking water. However, these methods aren’t always practical for big operations, and high temperatures, especially if they continue through the night, can stress cattle for days. If cattle are bred to be sweatier, they would be able to dissipate more of their internal heat, increasing their resistance to heat stress.

“About 40 to 45 percent of the beef cattle in the U.S. are raised in tropical and subtropical areas, and that’s where we see heat stress affecting growth, production in general, and reproduction,” Mateescu said. “We feel that heat stress is a significant threat to food security that will only be exacerbated by the human population growth.”

Mateescu’s latest study investigated 2,401 Brangus cattle from two commercial ranches in Florida to understand the genetic underpinnings contributing to an animal’s ability to manage heat stress. Brangus cattle, a composite breed of Angus and Brahman, are typically raised in the southeast region. The breed demonstrates high meat quality traits from Angus and increased thermotolerance of the Brahman.

The team performed skin biopsies to examine the sweat gland area, depth, and length. All cattle were genotyped to identify genes associated with higher tolerance to heat stress.

“Resistance to high heat stress varies among individuals in a population. There’s a lot of biological variation, and this variation has a genetic component,” she said. “The work we published really suggests that genetic programs to improve this heat stress resilience are possible.”

Mateescu said that the team will examine what specific genes are responsible for the variation in cattle sweating moving forward. Once the genes have been identified, she is hopeful that a genetic test can be developed that producers could use to select and breed cattle to be sweatier.

“All the traits that we looked at are not traits a producer can measure easily because they are expensive and difficult (to test),” she said. “If producers had a genetic test, they could use it to select cattle.”

Genetic tests would be an energy-efficient, sustainable solution to address global climate change, Mateescu said. She added that genomic selection programs could be developed through the use of genetic testing to help researchers and producers select more heat-resilient cattle. Producing sweatier cattle benefits not only producers, but the welfare of cattle, too.

Sweating is the main mechanism for cattle to dissipate internal heat, but there are other factors that contribute to how easily cattle can cool down. One property is the animal’s coat: cattle with shorter and slicker hair fare better in hot and humid conditions. For example, Mateescu and her team previously found that cattle with excessively smooth coats had lower body temperatures over a five-day study period.

The team also found that animals with slick, dense coats had greater resistance to heat transfer to the skin, reducing heat gain from the environment, and smooth coats minimized heat gained from the sun by providing greater resistance to heat transfer to the skin. Coat color also impacts heat tolerance, with lighter-colored cattle absorbing less heat than those with dark hair.