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Heat Stress in Cattle: Recognizing the Signs and Tips to Keep your Cattle Cool

By Kable Thurlow

Hot summer temperatures, currently climbing near the triple digits, combined with high dew points can cause significant heat stress to cattle. Heat stress is magnified when high temperatures continue into the night. The combination of high day and nighttime temperatures prevents cattle from properly cooling.

Tips to Keep Your Cattle Cool
Here are some simple tips from Michigan State University Extension to make sure your cattle stay comfortable:

  • Avoid handling, transporting, moving, or processing cattle. If cattle must be handled, work them in the early morning hours using low-stress handling techniques.
  • Provide additional water. For cattle on pasture, provide additional water supply, especially if they only have access to one tank in the pastures. Provide additional tank capacity as water intake increases. Check to make sure that water sources are clean and free of contaminants, defecation in a small portable watering tank will prevent cattle from drinking. Cattle prefer water between 40 -65 degrees F, water intake decreases when water temperature exceeds 80 degrees F. Producers can help keep the water cooler by ensuring that the water lines are covered by grass in the fence rows.
  • Observe cattle for abnormal behavior. Problems often occur during stressful events. Watch cattle movement, location and behavior for indications of problems. Have a backup plan ready if power or water systems fail.
  • Provide shade. During heat stress days, shade is critical especially for dark-haired, fleshy, young and older cattle. Shade can easily be provided by allowing access to pasture with trees or providing access to open buildings. If shaded pasture acres are limited these pastures must not be grazed during the days with normal temps so that pasture forage will be there when heat stress temperatures arrive.
  • Provide adequate ventilation. If cattle are being fed and housed in an enclosed barn or building, use fans to move air out or through the building or open sides of the barn or provide access to an outside pen or pasture with shade. Using sprinklers in this situation will potentially intensify the problem and create more humidity without proper air movement to remove it from the building.

There are several stages of heat stress with the following indicators. When first signs of heat stress are observed, minimize the stress immediately with the tips above. Early intervention is the key to survival, especially providing intervention in the evening when cattle are trying to dissipate heat from the day.

Signs of Heat Stress
The following are signs of heat stress, per the USDA’s Agricultural Research Service:

  • Stage 1: elevated breathing rate, restless, spend increased time standing
  • Stage 2: elevated breathing rate, slight drooling, most animals are standing and restless
  • Stage 3: elevated breathing rate, excessive drooling or foaming, most animals are standing and restless, animals may group together
  • Stage 4: elevated breathing rate, open mouth breathing, possible drooling, most animals standing, animals may group together
  • Stage 5: elevated breathing with pushing from the flanks, open mouth breathing with tongue protruding, possible drooling, most animals standing and restless
  • Stage 6: open mouth breathing with tongue protruding, breathing is labored, and respiration rate may decrease, cattle push from flanks while breathing, head down, not necessarily drooling, individual animals may be isolated from the herd.

Stress Categories

The chart below illustrates stress categories as defined by predicted breathing rate.

Predicted Breathing Rate

Heat Stress Category

Less than 90 breaths per minute

Normal

From 90 - 110 breaths per minute

Alert

From 110 - 130 breaths per minute

Danger

Above 130 breaths per minute

Emergency

Beef producers also need to be aware that heat could have implications which may not be seen immediately. If you are in breeding season with your cow herd, heat stress could result in early embryonic death loss of the new fetus in the first few weeks after conception. For bulls preparing for breeding season, high temperatures could impact semen quality for several weeks, resulting in lower conception rates a month after the heat stress event. Reduced conception risk is a possible outcome and key reason producers should keep cow herds cool during times of high heat index weather.

Source: msu.edu