Jim Kokes knows sprinklers will keep his cattle cool during South Dakota's soaring summer temps. But the feeder also knows tiny water droplets can do more harm than good.
"Sprinklers help cattle diffuse heat coming from both the ambient temperature and the rumen during digestion," Kokes said. "But water droplets can't be too small or too big if you want to avoid increasing humidity or creating mud."
Feedlot humidity levels are always a concern, said Warren Rusche, Extension cow/calf field specialist at South Dakota State University. A fine mist can increase moisture in the air without doing much to cool penned cattle. So what is the right-sized droplet? It's nearly impossible to give an exact recipe for what will work best in every operation.
"There isn't a specific range for sprinkler droplet size," Rusche said. "Just don't create fog or mist. Droplets should be big enough to soak down through coats, diffusing body heat. Also, a sprinkler should be set to throw water far enough out so cattle won't bunch up underneath it."
High temperatures, high humidity and the absence of air movement make it difficult for cattle to dissipate heat, increasing risk of illness or, in extreme cases, even death. Under very dry conditions, cattle can tolerate 85 degrees Fahrenheit without much difficulty. Add high levels of humidity, and the same animals could be under very severe heat stress at that same, or a lower temperature. Nighttime cooling plays a major role, as well. When temperatures stay above 70 degrees at night, there is a much greater risk of loss to heat stress.
Kokes worked with Heine Electric and Irrigation, in Hartington, Nebraska, to find effective sprinkler end guns that would cool about 200 cattle in each of six pens. Owner Dan Heiman used pen size, water pressure and Kokes' sprinkler-rotation plan to select the best gun for the job.
"Jim was looking for a gun that put out a lot of water in a 160-foot circle," Heiman said. "We selected a Nelson Big Gun. It's a higher-priced gun than some brands, but Jim will probably get 20 years of life out of it."
The Nelson gun provides slow, steady and uniform forward- and reverse-drive action, giving Kokes stable and consistent results. His Rainbird irrigation panel automatically activates and turns the sprinklers off, allowing each one to run two minutes every two hours between 11 a.m. and 7 p.m.
"Before we really need to use sprinklers, we set them to come on a few times at midnight and 3 a.m.," he said. This testing also allows cattle to get used to the hissing sound, so they won't run away when they come on. Once cattle get used to the sprinklers, however, they congregate around them.
Kokes runs his sprinklers at a pressure of 75 pounds per square inch (psi), drawing about 50 gallons per minute (gpm). He's careful to avoid increasing soil-moisture levels beyond 40%, a point at which odor and mud become issues. Because he wants to avoid drawing down water fountains when sprinklers run, Kokes uses a Y-configuration to separately feed fountains and sprinklers from one main water line.
"We run a 4-inch pipe from the well to the sprinkler and fountain shutoffs," Kokes explains. "From there, we use 2-inch pipe, one feeding fountains and one feeding sprinklers. Each sprinkler has a 24-inch culvert fit around it like a sleeve. Concrete fills the culvert, stabilizing the sprinkler."
Kokes had the perfect opportunity to install an effective sprinkler system with his new feedlot, but most feedlots can be retrofitted with a similar system. Water pipes can be run down a fenceline so there's no need to bury anything in an existing feedlot. The end guns Kokes chose cost between $500 and $800, but Heiman said some guns now cost as little as $25. More costly end guns have higher water-handling capacity, sprinkle water over a larger perimeter and can be adjusted to sprinkle in either a half- or full-circle.
In Kokes' system, stops can be set to avoid sprinkling outside the feedlot, and psi can be adjusted according to water availability.
"Jim's system is unique in that he was able to operate his sprinklers and fountains from the same main line," Heiman added. "He can shut sprinklers off in winter and let the water drain back to fountains. The culverts not only stabilize the sprinklers, they keep cattle from rubbing on them. With his control panel, he's able to set his sprinklers up just about any way he wants."
For More Information:
More details about the Big Gun are available at www.nelsonirrigation.com
Additional information about Heiman's company is available at www.heineelectricandirrigation.com
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