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Beat heat stress with these cool tips

March 14, 2018
Beat heat stress with these cool tips

Photo Credit: Alamri/Arizona Sonora News Service/

With temperatures exceeding 80⁰ Fahrenheit (F), cows can produce 4,500 to 6,000 British thermal units (BTU) per hour, an amount similar to the output of a 1,500-watt hair dryer. Heat can have serious manifestations in the dairy cow, resulting in effects such as (but not limited to):

• Lower production

• Rumen acidosis

• Milk fat depression  

• Poor reproduction

• Laminitis/lameness

• Weakened immune system

• Mastitis

• Transition disease (retained placenta, displaced abomasum, etc.)

• Lower body condition  score

It is only natural when cows are moved to a small space, such as the holding pen, that body temperatures rise. Research shows that a cow’s body temperature will increase by 3⁰ F in 20 minutes in a holding pen where there’s no cooling. By contrast, a cow’s body temperature will drop by 3.5⁰ F in that same 20 minutes when fans and a soaker system are used. Research by the University of Arizona showed that simply cooling cows in the holding pen increased milk production by 1.7 pounds per day in the summer.

There are can be adverse effects when developing a cooling system for holding pens if incorrectly applied. Water without fans will lead to increased humidity and heat stress in the holding pen, creating a “sauna” effect. Heat stress is a result of both temperature and humidity. The temperature-humidity index (THI) threshold for reproduction is 65,which is lower than the THI of 68 for milk production

Holding pen cooling tips:             

  • Mount fans in rows, with airflow toward the back of the holding pen.
  • Place 36-inch fans every 20 to 24 feet, or place 48-inch fans every 24 to 36 feet.
  • Put 3 feet between fans (for example, between 36-inch fans mounted on 6-inch centers).
  • Fan height should be a minimum of 8 feet, as low as possible but out of reach of cows and machinery.
  • Mount fans higher if drop hose soakers like i-Wobs are used.
  • For narrow holding pens (less than 24 feet) or pens with low ceilings, fans can be alongside the pen.
  • Move air across and toward the back of the holding pen.
  • Take advantage of prevailing winds.*

*Prevailing winds may be blocked by cattle, freestall dividers or headlocks. Wind speed is typically variable and is not dependable for adequate cooling of cattle.

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