Every season brings new and different challenges to farming operations in the Ozarks, and summertime is no different.
With summer comes heat, humidity and sometimes drought – all things that can cause heat stress in livestock.
Heat stress can cause many issues for a stockman, and it pays to be able to recognize signs of heat stress in your animals so that you can take immediate action if it occurs.
Heat stress occurs when the body cannot cool itself enough to maintain a healthy temperature.
Over exposure to hot, humid conditions, or being in cramped quarters on a hot day with poor ventilation can cause heat stress in livestock.
Earl Ward, Oklahoma State University Cooperative Extension Northeast District livestock specialist, reminds producers that cattle’s upper critical temperature is not based off of ambient temperatures alone, but also the humidity and evaporation rate.
“Humidity is an additional stress that intensifies ambient temperature problems by making body heat dissipation more difficult,” he said. “In other words, it can be tough to cool off in Oklahoma during the summer, for people and cattle.”
High humidity contributes to the likelihood of heat stroke or prostration because water evaporation from the oral and nasal cavities is decreased, in spite of rapid panting, a heat regulatory device in cattle.
“Although cattle sweat, the primary mechanism they have to remove internal heat is by panting to increase evapotranspiration, which is accomplished much more efficiently in low humidity environments,” Ward said.
“Heat stress shows itself in several ways. High respiration rates, drooling and open-mouth breathing are classic visible signs,” Eldon Cole, University of Missouri Extension Livestock specialist said. “Of course, checking body temperatures is another way. The normal cattle temperature is 101.5 degrees. Under heat stress conditions the temperature may rise to 105 or more.”
If possible, cattle and other livestock will try to alleviate heat stress on their own.
“Stressed cattle seek shade, mud holes, ponds, creeks and good air movement,” Cole said.
To combat heat stress, producers should make sure they are providing livestock with plenty of fresh water and plenty of shade.
Overheating in cattle can be prevented under most management conditions by allowing cattle access to cool water, and mineral supplements are a must during hot summertime weather.
Experts recommend increasing the number of watering locations, if possible, during the heat of summer, allowing cattle to spread out at water will increase air flow, which will reduce heat stress;
Oklahoma State University Cooperative Extension also reminds producers that water consumption will increase by more than 50 percent when temperatures are at or above 90 degrees Fahrenheit.
Finally, be aware of the situations you place your livestock in during the hot summer months.
“Stress levels may get serious when working cattle or hauling them. Pay especially close attention at these times and work them in cooler parts of the day,” Cole cautioned.

Stages of Heat Stress in Cattle

State 1
• Elevated breathing rate
• Restless
• Increased standing time.
Stage 2
• Elevated breathing rate
• Slight drooling
• Most animals standing in pen and restless*
• Animals may group together*
Stage 3
• Elevated breathing rate
• Excessive drooling or foaming
Stage 4
• Elevated breathing rate
• Open mouth breathing
• Possible drooling
Stage 5
• Elevated breathing rate with pushing from flanks
• Open mouth breathing with tongue protruding
• Possible drooling
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 herd
* Note: This symptom may be seen in multiple stages.


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