Help beef cattle manage heat loads as temperatures rise

“Heat stress on our cattle is a critically important aspect of our production that we have to control,” says A.J. Tarpoff, Beef Cattle Veterinarian with Kansas State Research and Extension.

Heat stress is a challenge that costs the U.S. cattle industry up to $370 million in losses each year due to decreases in performance, fertility, and increased potential for mortalities. Just like producers plan for colder temperatures, very warm temperatures need mitigation measures and a plan of action.

For starters, monitoring and forecasting tools are available to help producers and feeders plan ahead. One source Tarpoff recommends is the Heat Stress Outlook from the U.S. Meat Animal Research Center (MARC) in Clay Center, Neb.¹

As a seven-day forecast tool for the United States, the Heat Stress Outlook combines National Weather Service data and anticipated humidity, wind speed, and solar radiation into an animal comfort index.

Factors of heat stress

Cattle are resilient animals that often acclimate to hot temperatures, Tarpoff points out. But an accumulation of factors — including humidity, solar radiation, hide color, diet, and more — can drastically change a bovine’s ability to withstand summer’s heat. This was the case in western Kansas in early June 2022 when moisture followed by high daytime heat, high humidity, low wind speeds, and hot overnight temperatures created the “perfect storm” for heat-stress-induced death losses in feedlot cattle.

“It really is a multi-layer challenge,” Tarpoff says. “Each animal within a group or pen is not affected the same way. Animals with higher body condition scores, or with darker hides, or finisher steers and heifers that are getting ready to go to harvest are at higher risk of heat stress.”

Heat stress decreases the reproductive efficiency and performance of cattle grazing on pasture, Tarpoff says. In confined facilities, heat stress often causes cattle to eat less, which also negatively affects performance.

The human body cools itself on a hot day by sweating, called evaporative cooling. But Tarpoff notes that cattle sweat only 10 percent as much as humans, and panting is their primary way of dissipating heat.

“As temperatures rise and their heat load increases, they will start breathing faster,” he says. “They are dissipating heat through tiny droplets in the respiratory tract.”

Doing so, however, causes cattle to eat less.

“This all has to do with heat load,” Tarpoff says. “The internal temperature of cattle will peak two hours after the hottest point of the day. So our strategy for keeping cows cool needs to be built around knowing that.”

Another factor is that cattle produce heat by digesting feed, typically 4–6 hours after eating. “So if we feed animals within the wrong period of time, we can actually increase their heat load because the heat of digestion and the heat from the environment are building on top of each other,” Tarpoff says. “We want to keep that from happening.”

How cattle dissipate heat

“Cattle are robust species. They actually accumulate heat during the day and dissipate it during the nighttime cooling hours. So anything we do to maximize the nighttime cooling helps out the animals in the long run,” he says.

“It takes about 6 hours of nighttime cooling to be able to dissipate the cumulative heat load that they’ve picked up during the day.”

Without night-time cooling hours, animals don’t start each day at thermo-neutral, Tarpoff explains, so they’re more at risk on the second or third day. He says temperature, humidity, solar radiation and, most importantly, wind speed, all play a role in heat dissipation.

Producers can help manage the heat load bovines accumulate during a hot summer’s day:

• Provide plenty of cool, clean water. Consumption is critical. “When the temperature goes from 70° to 90°F, cattle will consume about double the amount of water,” Tarpoff says. As a rule, cattle should consume “about five times the amount of water as the dry matter they are consuming. We may have to increase the water tank capacity within a pen to meet these needs with portable water troughs. Producers need to be prepared for that.”
• Modify feeding times. Feed 70 percent of the animals’ ration as late in the evening as possible, which puts the peak heat of digestion overnight when temperatures are likely cooler. Decrease feeding during the day.
• Receive, ship, or move cattle only during the coolest parts of the day. Move before 8 am and never after 10 am. Keep in mind that handling cattle in the evening won’t necessarily reduce heat stress risk.
• Implement factors like these:
  • Split cattle between pens or reduce stocking density.
  • When processing, work cattle in smaller groups so they’re not standing in the holding area longer than 30 minutes.
  • Don’t overcrowd working facilities, work cattle slowly, and use low-stress handling techniques. Processing cattle in any temperature elevates the animal’s core temperature.
  • Maximize airflow by removing obstructions around facilities, including weeds. A windbreak 10-feet high can obstruct air flow 100-feet downwind.
  • Modify pen surface. “Keep in mind that just a dirt floor, due to the solar radiation, can get up to about 140 degrees,” Tarpoff says. Dry bedding such as straw can drop the surface temperature of that pen floor, he says, by about 25 degrees.
  • If feasible, install shade structures, which can reduce solar radiation and reduce the temperature on the pen floor. Keep in mind that each animal needs 20-square-feet of shade access or animals will bunch, making this management factor null and void.
  • Install sprinklers to wet cattle down at night or early morning so as not to increase humidity.
  • Control biting flies. Stable flies cause cattle to bunch and disrupt cooling. Removing weeds and brush within 150 feet of pens and spraying the shaded areas of buildings with a residual insecticide can help control stable flies and their breeding habitat.

¹Heat Stress Outlook: https://www.ars.usda.gov/plains-area/claycenter-ne/marc/docs/heat-stress/main