The installation of fans last summer could very well be the “best thing we ever did,” says Kevin Miller, dairy herd manager at the Krauss Dairy Center in Wooster, Ohio. When Miller recalls last summer’s milk production, he can tell you with confidence that the fans “definitely made a difference” in cow comfort. In fact, the cows produced an additional 1,500 pounds of milk per day compared to previous years without the fans. 

Of course, the Krauss Dairy Center, located at the Ohio Agricultural Research and Development Center, couldn’t have achieved this success without proper fan management. 

Use these ideas to help you get the most out of your fans and to provide effective cow cooling this summer. 

Position Fans Properly
To get good results from your fans, place them in areas that benefit the cows the most. Heat stress experts recommend that you place fans in the holding pen first, followed by areas which house cows with special needs, such as your close-up, maternity and hospital pens. Then, place fans along the feed bunk to encourage feed intake. Finally, place fans over the free-stalls. 

Remember, a combination of water, such as a sprinkler or mister system, and fans will be the most effective way to cool cows, stresses Dave Bray, dairy scientist at the University of Florida.  This is particularly critical in the holding pen, he adds.

Next, consider how fan placement contributes to cow cooling. Effective cooling occurs when fans are spaced properly and orientated in the same direction. Use the following guidelines to help you properly place fans in a holding pen, along a feed alley and over free-stalls:

• Holding Pen
  Whenever possible, place fans within the holding pen, with airflow directed away from the parlor. If this isn’t possible in your holding pen, consider placing fans along one side or both sides of the holding pen, suggests Rick Stowell, agricultural engineer at Ohio State University. When at all possible, work with the direction of prevailing summer breezes.

• Free-stall barns
  In a free-stall barn or drive-through feed barn, your first goal should be to cool cows at the feed bunk to encourage feed intake. Position fans so they blow air over the cows’ backs when the cows are eating along the feed bunk. If you want to go one step further, you can also position fans so they blow air across the cows’ backs when they are lying in the stalls.

Mount fans on posts or truss chords at a height that provides clearance for equipment, such as your manure-handling and feeding equipment, Stowell suggests. (Please see "Fan Placement in a Free-Stall Barn" below.)

Create Airflow and Velocity
In addition to fan placement, your fans need to generate high airflow and velocity to maximize cow cooling.

At a minimum, the rate of airflow should be about 500 -- preferably 1,000 -- cubic feet per minute (cfm) per cow during warm weather, Stowell says. For example, a holding pen with a group of 80 cows needs a minimum airflow rate of 40,000 cfm (500 cfm x 80 cows = 40,000 cfm).

In addition to airflow, pay attention to air velocity, or how fast the air is moving past your cows.  Air velocity measures the speed of air in feet per minute, similar to how your car’s speedometer measures how fast you are driving. Aim for an air velocity of at least 220 -- preferably 500 -- feet per minute. That’s equivalent to 2,5 to 5.5 miles per hour, Stowell says.

Fan Placement in a Free-Stall Barn In a free-stall barn or drive-through feed barn, place fans so that htey blow air over the cows' backs when they are standing along the feeding alley or lying in the stalls. Mount fans on posts or truss chords at a height that provides clearance for commonly-used equipment. And, provide a clearance of at least 8 feet above the free-stall floor. Adjust Fans Properly Use this simple procedure to orient airflow over your cows' backs: Tilt each fan downward -- about 30 degrees -- so that it is aimed at the floor below the next fan line. Illustration: On the Draw Graphic Design, Ltd. Source: Rick Stowell, Ohio State Univ.

To accomplish sufficient airflow and velocity, position fans according to their effective “throw,” or the distance at which airflow is sustained. Typically, a fan will blow air over a length equal to about 10 times its diameter, Bray says. A 36-inch fan (3-foot diameter) is usually designed to cover an area up to 30 feet long, while a 48-inch fan (4-foot diameter) should be spaced every 40 feet down the length of the area that you want to cover. For example, in a special needs facility which contains a bedded pack, space 36-inch fans every 30 feet down the length of the bedded pack.

Of course, if the distance between posts in a building measures less than 30 feet, it’s OK to place fans closer together, Bray says. That’s the case at Krauss Dairy Center in Ohio. In fact, the 36-inch fans are spaced every 24 feet apart along both sides of the feed alley. Just remember, you don’t want to exceed 30 feet apart for 36-inch fans or 40 feet apart for 48-inch fans. 

Fan Maintenance Guide
A clean, well-maintained fan can help you cool cows effectively. Rick Stowell, agricultural engineer at Ohio State University, suggest the following maintenance tips to keep your cooling fans in top-notch condition this summer:

1. Examine belts on a yearly basis. Replace worn or broken belts promptly. 
2. Repair bent or broken fan blades and fan housings quickly.
3. Monitor thermostats and clean sensors at least once per year.
4. Inspect fan blades and housings a few times during the summer. If they are covered with dust, they need to be cleaned.
5. Remove or adjust fans which are placed within reach of equipment or cows.

Reprinted with permission from Dairy Herd Management.