Here are a few ideas we can share with you concerning heat stress in your milking herd. In priority order, cooling needs to be placed in 1) the holding area, 2) along feed bunk, and 3) over free stalls.

1. We must use fans AND sprinklers in the holding area and by the feed bunks. One without the other WILL NOT result in effective evaporative cooling. In the free stall area, you could go with fans only to avoid water in the bedded stalls.

2. Use either 36" box fans with a cfm rating of approximately 11-12,000 or 48" fans with a cfm rating of approximately 20-21,000. These fans run on 1/2 or 1 hp motors.

3. Fan placement:
* In the holding area, place fans side by side every 8 to 10 feet, and blow across the width of the holding pen. (Use 36" fans if pen is approximately 30' wide, or 48" fans if pen is 40' wide). The 8 to 10' side-by-side distance can be stretched if the number and cost of fans is too much.
* Over the feed bunk, place the fans at a 30-degree angle so that they blow down toward the floor. Place the fans every 30' for a 36" fan or every 40' for a 48" fan.

4. Set fans on a thermostat and the sprinkler on a timer to go on at 78 to 80 degrees F. Depending on the nozzle output, allow the timer 2 to 3 minutes on and 12 to 13 minutes off. Fans should run continuously after they kick on to avoid wear and tear on the belts and motors. Do not allow water to be sprayed on the fans.

5. Sprinklers in the holding area should provide a 360-degree spray pattern and be spaced as far apart as the radius of throw for each sprinkler. Sprinklers over the feed bunk should use a 180-degree spray pattern to allow wetting the cow without wetting the feed. Hang at a height to avoid contact with cow and total mixed ration equipment. Direct spray over the cow's shoulder and back for a quick soaking. Select nozzles with a 0.5 to 2.0 gallon per minute (gpm) output that run with a low pressure of about 10 psi. Water pipe size will depend on nozzle flow, number of nozzles, and length of water line. PVC pipe works well. You will need to adjust the on-off cycle to get the wetness you want, depending on the water flow. You want the cow's back soaked but not too much water that it reaches the udder. Space the nozzles to provide overlap coverage spray.

6. In the free stall area, hang the fans over the rows to blow on the cow's head, and space the fans approximately every 30 to 40 feet apart depending whether they are 36" or 48" fans. Also direct downward at a 30-degree angle, and set fans just high enough to avoid cows tampering with them.

Dave Fischer, Extension Dairy Educator, University of Illinois - Illini DairyNET