American Society of Animal Science
American Dairy Science Association

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News from the Midwest Sectional Meetings, March 16-18, 1998, Des Moines, Iowa

Contact:
John Smith, Kansas State University, (785) 532-1203
Tom Jirik, ASAS/ADSA Media Coordinator, North Dakota State University, (701) 231-9629

Bringing Temperatures Down Keeps Dairy Production Up

DES MOINES, Iowa – Keeping dairy cows from overheating during hot weather is a key to maintaining production levels and reproduction, a dairy expert from Kansas State University says.

"Heat stress can cause losses in production of 20 percent or more and reduce conception rates from 10 to 20 percent," says John Smith an extension dairy specialist. Producers need to look for ways to reduce that stress without adding significant costs to production, he adds.

Dairy experts agree that heat stress for dairy cows begins to take its toll when the temperature/humidity index reaches 72 degrees. "The severity and duration of the heat stress is going to depend on local conditions. In some areas, heat stress is almost never a concern, and in others, it’s nearly constant," Smith says. "That means the steps taken to reduce heat stress will be different on every farm."

In a presentation to researchers and extension specialists at the joint Midwest meeting of the American Dairy Science Association and the American Society of Animal Science in Des Moines, March 17, Smith outlined key strategies for reducing heat stress. He recommends adopting the recommendations in the order they’re listed here. Each step to reducing heat stress comes with a cost, he notes, so producers need to carefully consider whether the benefits will justify the expense.

• • First, provide adequate cool, clean water. Smith says providing enough water for cows as they leave the milking parlor and in housing will go a long way toward keeping cows cool. Cows rely on evaporation of moisture from the respiratory tract and from sweating for cooling. In dehydrated cows, this natural cooling system is crippled.

• Second, find ways to reduce walking distance to the milking parlor. Minimizing effort helps cows keep their cool, Smith explains. And minimize time cows spend in the milking parlor’s holding pen. "Those cows are like a bunch of large furnaces in a small room with no place for the heat to go," he says.

• • Next, provide shade in the holding pen and in cow housing. Keeping the sun off cows can dramatically reduce temperature.

•Provide a holding pen cooling system and exit lane cooling. Smith notes that the holding pen and parlor are relatively harsh environments because of the amount of heat generated in that small space. Although fans and sprayers are expensive, keeping cows cool in the holding pen and cooling them rapidly as the leave the milking parlor may reduce stress enough to make those systems pay, he says.

• Finally, provide cooling systems in cow housing ares and along feedlines. Although this is the most expensive option for cooling cows, it may be necessary to keep cows producing at optimum levels.

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