Cattle ranchers are pointing to the dangerous conditions persisting through the south and parts of the midwest that are significantly raising the risk of heat stress in the herds. It can be a common theme this time of year when hot temperatures combined with other environmental factors often create safety hazards for livestock. With forecasters calling for above-average temperatures across much of U.S. cattle country for the remainder of July and August, livestock producers will need to remain vigilant throughout the summer.

Heat stress is estimated to cost the U.S. cattle industry as much as $370 million in losses every year. The conditions trigger a cascade of events that impact a bovine’s production ability, make it susceptible to disease, and in extreme circumstances, even death.

Compared to other animals, cattle cannot dissipate their heat load very effectively. A compounding factor on top of climatic conditions is the fermentation process within rumens that generates additional heat. As such, cattle accumulate a heat load during the day and dissipate heat at night when it is cooler. It takes at least six hours to fully dissipate the heat load. During extreme weather conditions with insufficient environmental cooling at night, the heat load accumulates and animals can be at risk within the second or third day. By the time animals do start showing external signs of heat stress, it’s already begun wreaking havoc on vital internal systems that can negatively impact productivity.

A.J. Tarpoff, a beef veterinarian with K-State Research and Extension, says that as temperatures rise, cattle will start breathing faster as part of their natural way of dissipating heat. Doing so, however, causes cows to eat less, setting them on a path to poor growth and future performance. The internal temperature of cattle peak about two hours after the temperatures in the surrounding environment peak, a factor he says is important to understand as it can play a role in helping reduce heat stress. He recently shared his list of best management practices with the Great Bend Tribune, which we have condensed below:

  • Feeding: Modify feeding times. Feed 70% 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.
  • Handling: Receive, ship, or move cattle only during the coolest parts of the day, preferably before 10 a.m.
  • Managing heat: Split cattle between pens or reduce stocking density. Maximize airflow by removing obstructions around facilities, including weeds. If feasible, install shade structures, which can reduce solar radiation and reduce the temperature on the pen’s floor. Install sprinklers to wet cattle down at night or early morning so as not to increase humidity.
  • Water: Lots and lots of water. “To put it into perspective, when the temperature goes from 70 degrees Fahrenheit to 90 degrees, cattle will consume about double the amount of water,” Tarpoff said.

Heat stress risk can be forecast by measuring four key paramaters: temperature, wind speed, humidity, and cloud cover (aka solar radiation). The USDA’s Agricultural Research Service has a handy tool that does just that using data from the National Weather Service. The Heat Stress Forecast Maps are made using the seven-day forecasts of the four heat stress parameters. The most recent forecast shows heat stress risks persisting at emergency levels in the south and some parts of the midwest. The map is broken out into 6 different regions that you can zoom in on for more details. The website also has a lot of other information about heat stress and ways to manage it. Check it out HERE. (Sources: Drovers, Bovine Veterinarian, USDA, Great Bend Tribune)

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