This summer’s high temperatures are taking their toll on humans and cattle.
Extreme heat actually is a mix of temperature and humidity, and when both are high, the effort to stay cool can be stressful, according to Karl Hoppe, North Dakota State University Extension livestock systems specialist at the Carrington Research Extension Center.
Cows will look for shade to provide some relief from heat radiating from the sun. They’ll also seek a wind or breezy location to provide some evaporative relief, and water, mostly for drinking and some for cooling.
“Adequate drinking water is the first step in relieving heat stress,” Hoppe says. “During hot weather, cattle will substantially increase water intake. It’s important to have enough drinking space and adequate water reserves to allow cattle to drink and not fight with other cattle for water.”
Depending on their size and stage of production, cows can require 15 to 30 gallons of water per day.
“The minimum livestock storage tank capacity should be enough to meet the minimum water requirements for the number of animals being grazed per day,” says Miranda Meehan, NDSU Extension livestock environmental stewardship specialist. “The water tank should supply adequate water for two to three days using an electric (hard-wired) pump or three to seven days using a wind- or solar-type pump.”
Because of cattle’s need for water, producers should be extremely diligent about monitoring water sources on hot days, the specialists say.
“Hot, dry conditions support the growth of blue-green algae (cyanobacteria), which is toxic to livestock,” Meehan adds. “Ponds that had adequate-quality water for drinking early in the grazing season may become toxic because salts and sulfates become more concentrated as water evaporates.”
If water quality is a concern, immediately collect a water sample and have it tested for total dissolved solids (TDS) and sulfates. Greater than 3,000 to 5,000 parts per million of TDS would indicate the water is poor quality and producers should find alternative water sources.
Biting flies also create stress on cattle. To lessen fly stress, cattle will bunch together. This reduces the wind that can get into the middle of the herd and exaggerates heat stress.
Bunched cattle also can create a dust cloud on dry days. Too much dust can lead to breathing stress. When the weather is hot, cattle with reduced lung function can be identified easily; they may have labored breathing with increased panting, their tongue may be hanging out and they may be frothing at the mouth.
Hoppe says feedlots use water sprinklers to cool the pen surface or wet the cattle. However, spraying water can lead to increased localized humidity, which on hot day may create more heat stress than relief.
Cattle with white hides will reflect sunlight and tend to handle heat better than black-hided cattle. However, in winter, black-hided cattle may enjoy the solar heat-collecting properties of their hide.
In North Dakota, the nighttime temperatures usually fall below 72 F, giving cattle an opportunity to cool. When the temperature doesn’t drop below 72 F, cattle remain stressed, and after two or three days, they can develop heat stress.
“When several days of hot and humid weather are forecast, be proactive and create cooling opportunities in the morning before cattle start panting,” Hoppe advises. “Cooling options are more water tanks with easy access, moving cattle to shade and away from windbreaks, and controlling flies.”
The specialists also suggest producers sign up for the Cattle Heat Stress Forecast Maps (https://toolkit.climate.gov/tool/cattle-heat-stress-forecast-maps) to receive alerts about cattle heat stress conditions in their location. The U.S. Department of Agriculture’s Agricultural Research Service offers daily maps with seven-day forecasts of temperature, humidity, wind speed and cloud cover based on information from the National Weather Service.
For more information about heat stress, water requirements and water quality, check out these NDSU Extension publications: