Anything that helps cattle dissipate heat during hot weather reduces heat stress, and sprinklers can be used for this purpose.

Water dampens the animals (increasing evaporative heat loss) and cools the ground -- increasing heat loss through conduction (movement of heat from the animal). Don Spiers, Professor of Animal Science, University of Missouri, Columbia, says if cattle lie on hot ground, the heat can't get away.

When spraying cattle, Spiers recommends using cool or lukewarm water. "Cold water makes blood vessels in the skin contract and shut down. Cool or lukewarm water allows vessels to stay dilated, to keep bringing overheated blood to the body surface for cooling. With cold water, vessels contract and body temperature will rise even higher," he says.

He also warns against putting too much water into the air, increasing humidity. "Then the animals can't lose heat through evaporation. In a desert situation with hot, dry heat, evaporation works, but if you have heat and humidity, it's harder to deal with.

"Usually humidity goes down during the day as air temperatures rise, unless you've had rain. When temperature drops at night, humidity goes up. We often use evaporation during the day when it gets hot, because humidity has dropped. But if you've had rain and heat, the air is already full of water," says Spiers.

He says it's better to use large droplets rather than mist. "You must get water on the skin for evaporation to be effective. A mister increases humidity, and the water clings to the hair and doesn't make it to the skin. If you spray on too much and it's dripping off the animal, it does no good; you are wasting water.

"It must evaporate from the skin to cool the animal. The general cycle is to use water for about five to 10 minutes of wetting, several times per hour, on and off. This gets the needed moisture to the skin and allows time for it to evaporate," says Spiers.

Several irrigation companies sell feedlot sprinkler systems, aimed at dust suppression and cooling, and designed for uniform pen coverage. Feedlot Environmental Systems of Boise, Idaho, goes all over the country to install automated systems. Dewayne Christensen says Simplot is their largest customer, and they also service 26 other feed yards throughout the West -- from Texas to Washington state.

Don Zimmerman of Nelson Irrigation Corporation of Walla Walla, Wash., says in Nebraska's 1999 heat wave sprinklers not only settled dust and kept down-wind neighbors from complaining, but also reduced heat problems. "Feedlots with sprinklers had 10 to 12 percent reduction in death loss, according to statistics from University of Nebraska, and a marked decrease in respiratory distress," says Zimmerman. Cattle deaths in Nebraska from heat and humidity exceeded 3000 during July alone that year, amounting to more than a $2 million loss--and economists estimated that feeders lost about 10 times that amount due to poor gains on the surviving cattle.

Keeping cattle cool increases feed consumption and prevents bloat. Christensen says sprinkler systems increase weight gain. "It controls dust and keeps health a lot better, but the real money saver is reducing heat stress so cattle aren't too hot during the day to eat. If they lie around and get up to eat in the evening, they eat too much and bloat. If you keep the temperature down, they eat more evenly through the day."

Some of the computer controlled sprinklers use weather systems to calculate how much water to put out. "By putting water on the ground, in repeat cycles, you allow for evaporation of the entire area; it cools the ground level of the pen (five feet of air space) about 10 to 15 degrees. When you look at a stress chart for an animal, and take 15 degrees off that danger zone, it moves them back into a safe temperature," explains Christensen.

Each nozzle covers a pen area, designed for uniform coverage all the way through the feedyard, on each cycle. "You know how much they're putting down, and what's needed, based on temperature, humidity and prevailing winds." It's all set up on the computer. "Independent weather stations at the yard sense solar radiation, temperature, wind speed and direction, humidity, normal temperature; it's fed to the computer to increase or decrease the time of the sprinkling cycle." These are permanent systems with pipes underground. Sprinklers are mounted on 8 foot risers. "We design and lay them out according to pen depths and lengths. You could have a row of pens with 10 to 20 sprinklers," he says.

"If pen configuration allows, we put them fencelines, but some feedyards are so large we put some in the middle of the pens. They are encased in concrete, built to withstand cattle rubbing, feed trucks or scrapers bumping into them," says Christensen.

Studies at the University of Nebraska looked at the impact of sprinkling on body temperature and performance of steers, and found average daily gain was increased 13 percent (and feed conversions improved 15 percent) by sprinkling. ©