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Cooling strategies for dairy cattle
May 16, 2013

During hot weather it’s difficult for dairy cows to regulate their  body temperature, says Alvaro Garcia, SDSU Extension Dairy Specialist.

“Body temperature regulation in dairy cows is constantly challenged by a  combination of environmental heat and the heat produced during rumen  fermentation and nutrient metabolism,” Garcia said. “Heat stress occurs  when cows cannot dissipate enough heat to maintain their core body  temperature below 101.3 °F. Air velocity also increases the maximum  threshold, suggesting cows housed in facilities with forced air can  tolerate higher ambient body temperature.”

Despite the recent cool temperatures of the early spring, temperatures  in South Dakota can turn warm very quickly, says Dennis Todey, SDSU  Extension Climate Specialist. He says this situation is expected during  the next couple days.

“As warm air from the south combines with locally dry conditions it  will allow temperatures to reach the 80s statewide,” Todey said.

Because of the cooler spring overall; the rapid shift may produce stressful conditions for livestock.

“The heat this week was preceded by unusually cool days and nights. At  this point, cows have not had the chance to acclimate. Cattle usually  need two to four weeks of gradual temperature built-up to adapt to  changes. Temperatures above the mid-80s can be very stressful,  particularly if there is little air movement and humidity above 50%,”  Garcia said.

Temperature, humidity, and stage of lactation

When temperatures exceed 75 °F however, intake drops considerably even  at 50 percent relative humidity. Intake is reduced at higher intakes  and/or productivity.

Garcia says that close-up and early lactation cows are the most  sensitive to heat stress and need more stringent cooling strategies. One  strategy he suggests is soaking them with water.

“Heat loss through the skin can be improved when both skin and coat are  soaked,” Garcia said. “Cows can tolerate greater body temperature  during the day when ambient body temperature during the night drop below  70 °F. Keep soaking them in the evening to help accomplish this.”

He adds that intake and production are more closely associated with the  temperature of the two previous days than those of the present one.

“Whenever necessary it is important to have strategies that reduce temperature at night,” Garcia said.

Cooling affects milk yield

In order for soaking to be effective, Garcia says sprinklers must soak  coat and skin and should work intermittently to allow time for water to  evaporate before the next soaking cycle.

Source: South Dakota State University & Dairy Herd Network


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