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College of Food, Agricultural, and Environmental Sciences


Producers Still Need to Watch for Heat Stress Signs in Livestock

July 12, 2012

COLUMBUS, Ohio – While Ohio’s heat wave with multiple 100 degree days has subsided, producers still need to watch for potential heat stress symptoms in their livestock as the animals are still dealing with hot and humid temperature swings and drought conditions, a pair of Ohio State University Extension experts said. 

Continued forecasts for ongoing hot, humid weather combined with drought conditions in many parts of the state can be of concern for livestock, said Stephen Boyles, an OSU Extension Beef Specialist.

Hot weather and high humidity can reduce breeding efficiency, milk production, feed intake and weight gains, and can sometimes cause death, he said.

“High temperatures raise the concern of heat stress on cattle, which is hard on livestock especially in combination with high humidity,” Boyles said. “Livestock should be observed frequently and producers should take precautions when hot and humid weather is forecast including working cattle early in the morning to decrease the risk of heat stress.”

Already, the majority of Ohio is experiencing moderate drought, with areas in the western and northwest areas of the state near the Indiana border experiencing severe drought as of July 10, according to the most recent U.S. Drought Monitor.

In fact, while temperatures are expected to cool somewhat over the weekend in much of the state, forecasters expect temperatures to rise into the 90s again next week. That is on top of the stress livestock faced last week, when temperatures reached over 100 in many parts of Ohio, with heat index values reaching upwards of 109 in many areas, meteorologists said.

For livestock producers, that means keeping abreast of weather forecasts and making contingency plans in the event of hot, humid conditions, Boyles said.

For example, the weather service issues special forecasts during extremely hot weather to alert livestock producers of dangerous weather, he said. The warnings are based on a temperature-humidity index, which increases as the temperature and humidity increase. The danger level is indicated by an index value of 79, which is reached in various combinations of temperatures above 85 degrees in combination with high humidity.

“As temperatures increase, slightly lower humidity can still create dangerous and emergency conditions,” Boyles said. “The emergency level begins at an index level of 84 and occurs at temperatures in the 90- and 100-degree range, increasing in danger as the humidity level increases.

“When temperatures hit in the mid-to-high 90s, producers need to pay more attention to cattle behavior.”

In addition to shade and improved ventilation, producers should ensure that livestock have access to cool, clean drinking water, said John Grimes, beef coordinator for OSU Extension.

For example, a mature bull that weighs over 1,600 pounds should drink 20.6 gallons of water a day on a 90 degree day, he said. 

“When the temperature gets over 90 degrees, they can consume an incredible amount of water just to keep cool,” Grimes said. “Producers need to make sure the animals get as much access to water as they can on a day like that to stay hydrated. 

“Shade is also a good move because the sun combined with the heat is hard on them.”

Other management measures include shading water pipes to keep the water cool and rotating livestock through fields at a more rapid rate, Boyles said. This is a benefit because taller grass tends to have a cooler surface than pastures with shorter grass stands, he said.

Producers could also consider feeding livestock in the evening, since cattle may eat more during the night than during the day in hot weather, Boyles said. Most importantly, he said, producers need to keep a keen eye on their livestock for signs of stress.

“Any good management practice requires you to look at your cattle’s behavior,” Boyles said. “If the cattle are all standing up, that could be a sign of heat stress because they stand as a coping mechanism to get heat out of their body.

“You should also look for crowding around the water source, cattle grouping together to produce indirect shading or open-mouth labored breathing.”

Tracy Turner
Stephen Boyles, John Grimes