July 19, 2002

LINCOLN, Neb. — Heat stress in livestock may be easier to control this summer because of lower humidity levels, but without proper management, summer heat still can take a toll on livestock health and productivity, University of Nebraska specialists say.

Light to strong breezes and moderate humidity can help livestock stay comfortable if the evaporative cooling potential of water is used effectively, said Rick Stowell, University of Nebraska animal environmental engineer.

The best option is to sprinkle cattle with large water droplets that penetrate the hair coat and let natural evaporative cooling aid the cattle, he said. Avoid a mist since fine droplets will not penetrate the hair coat, the Institute of Agriculture and Natural Resources engineer said.

"The goal is to intermittently soak the cattle's hair coats," Stowell said. "If you do not have sprinkler systems in place, these are the weather conditions that produce a high return on your investment so consider installing a simple system soon."

Hog barns also need sprinklers or misters – especially on pregnant and farrowing sows and larger finishing hogs – unless the hog barn is equipped with an evaporative cooling system, Stowell said. Sprinklers and misters should be placed over the pigs and controlled to minimize wasted water, which ends up in manure storage facilities.

Keeping livestock cool keeps them comfortable and reduces income losses, he said. When animals get too hot, they will stop eating and gain less weight or give less milk, Stowell said.

Cattle do not handle heat stress as well as humans, said Terry Mader, beef specialist at NU's Haskell Agricultural Lab near Concord. Young animals have a narrow comfort zone between 45 and 80 degrees. Feedlot cattle's and mature cow's comfort zones range from zero to 75 degrees, depending on body condition, hair coat length, coat color and diet.

Sprinklers need to be placed in areas where cattle will be every day, such as the holding area, feeding alleys and targeted areas of open lots, Stowell said.

Sprinklers should apply 1/20 to 1/10 of an inch of water in bursts every 15 to 30 minutes. Timed water applications and thermostats are recommended to keep sprinklers from operating during cool conditions, he said.

Mader said heat stress problems are worse during more humid years. However, this summer's drier air causes the potential for respiratory problems, such as dust pneumonia. Dust can be controlled by spraying the pen surface with water so livestock congregate around the cool surface and minimize dust.

Mader also suggests these management practices:

– Feed cattle toward evening to help them stay on feed and even out consumption patterns.

– Reformulate rations to lower the energy content by 5 to 7 percent, or lower total feed intake to minimize overall metabolic heat load.

– Schedule cattle handling between midnight and 8 a.m. – never after 10 a.m.

– Feedlots without good airflow need to be improved by reducing tall vegetation and abandoning pens with dead air spots.

– Remember to have ample water available.

– Higher temperatures mean a higher water requirement. Have an emergency plan if watering systems fail.

For more information on managing heat stress, consult NU Cooperative Extension NebGuide G00-1409-A, Managing Feedlot Heat Stress, available at a local extension office and on the Web.

07/19/02-SA

Richard R. Stowell - Ph.D.
Biological Systems Engineering
Assistant Professor
(402)472-3912

Terry Mader - Ph.D.
Animal Science
Professor
(402) 584-2812

Sandi Alswager Karstens
IANR News and Photography
(402) 472-3030

Department: Animal Science|Biological Systems Engineering