Evaporative cow cooling system.
June 26, 2017

Arizona Heat Wave Doesn’t Affect Milk Production

 |  By: Jim Dickrell

While humans wilted under the past week’s dangerous high heat conditions in Arizona, the state’s dairy cows were doing just fine.

That’s due to two factors: Virtually all the cows are now housed under shades equipped with evaporative cooling and the current heat wave is low in humidity.

“Our milk production is down very little,” says Keith Murfield, CEO of United Dairymen of Arizona, the state’s largest dairy co-op representing more than 80% of the state’s dairy farmers and an even larger percentage the state’s dairy cows.

Murfield says milk production would drop 40% under Arizona’s extreme heat. But most farms have now installed fans with misters, which can reduce temperatures 40° or more. The problems come later in summer, when weather systems turn more humid, with dew points reaching 55° to as high as 70°. Then, the evaporative cooling system don’t work quite as well and milk production can drop 10% to 15%.

Even though temperatures last week reached 120°F, the dew point was only about 20° and the humidity was 7% to 10%. Under those conditions, cows do just fine.

Paul Rovey, who milks about 2,000 cows, mostly Jerseys, says the heat has been harder on employees than on his cows.  All of his milking herd and close-up dry cows are under evaporative cooling. Even his calf barns are equipped with evaporative coolers.

“Last week was brutal, but the cows were doing reasonably well,” says Rovey. “We just made sure are employees were wearing hats and had plenty of water to drink.”

The challenge, he says, will come later in summer as humidity and dew points ratchet up. View a video on evaporative cooling under Arizona conditions here.