Much like humans, sweating is a key way for cows to regulate their body temperature and avoid overheating. Most cow breeds, however, do not sweat efficiently, which can be a real and sometimes deadly problem when outdoor temperatures are soaring. As more cattle production areas around the world are affected by extreme heat, scientists have identified the genes within breeds of cattle that could make them sweatier and more heat-tolerant.
“Heat stress is the main threat of food security,” says Raluca Mateescu, University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) professor in the department of animal science. Cattle stop eating when they are too hot, which ultimately impacts growth, production, and reproduction.
Cows become heat stressed when they generate and absorb more heat than they can easily get rid of by a combination of sweating and respiration (breathing/panting). Cows absorb heat from the sun when outside and generate heat by digesting food and producing milk. High-producing cows eat more and thus generate more heat.
According to Mateescu, cattle only lose about 22% of their latent heat through panting while the rest is lost through moisture from the skin surface when air temperature is greater than 30 °C/86 °F. At high temperatures, evaporative cooling is the dominant mode of heat loss in dairy cattle.
Not surprisingly, heat stress risk is highest in subtropical regions, which are the areas just north and south of the tropics and generally considered the hottest in the world. Approximately 45% of beef cattle operations in the United States are stationed in tropical and subtropical locations in the south and southeastern states where hot and humid temperatures are most prevalent.
In these environments, cows compensate for the hotter conditions by eating smaller meals and shifting feed intake to cooler parts of the day. Losses due to heat stress and reduced performance are estimated at between $300 to $900 million annually in the US. Manteescu says about $369 million of US beef production alone is lost annually due to reduced performance.
Mateescu’s study focused on Brangus cattle, a cross between Brahman and Angus, which came from two commercial ranches in Florida. Skin biopsies helped the researchers determine the phenotypes that contributed to the animals’ ability to manage heat stress, such as sweat-gland area, depth and length. Scientists genotyped all animals and used software to estimate genetic parameters.
Importantly, the study found a lot of variation between cows of the same breed. What’s more, the variation in sweating ability is genetic. This means that by selecting cattle based on specific genetic markers, farmers can cultivate herds that are better equipped to handle rising temperatures. As Mateescu warns, cattle unable to withstand increasingly hot temperatures are increasingly unlikely to reproduce, posing a threat to global food supplies.
The findings of this research have been published in Journal of Animal Science and Biotechnology and can be accessed HERE. (Sources: Phys.org, University of Florida, Reuters)
