Heat abatement up to par?

By Dr. Darin Bremmer
Heat stress can start to impact high-producing cows once the temperature reaches above 65 degrees F.  With warmer temperatures on the horizon, now is the perfect time to assess your heat abatement strategies and make any necessary changes to avoid substantial economic impacts.

Moving air
The first place you should start is with the fans.  Use a wind meter to measure wind speeds throughout the barn before you make any adjustments.  When measuring airflow, place the wind meter in the cow beds at the height of a cow’s head while she is lying down.  Ideally, wind speed at the cow level should be between 4 and 6 miles per hour.

Cross-ventilated and tunnel-ventilated barns should be assessed for any restricted air flow.  When given the chance, air will take the path with the least resistance.  The goal should be to force air back over the cow beds and feedbunk.  This can be done with baffles and fans.

Additionally, fans should be cleaned and set to turn on and continuously run at 65 degrees F.

Gathering places
The holding pen is one of the most important areas to address in any heat abatement program.  Soakers and fans are needed in this area due to the amount of heat produced and the difficulty to circulate air between cows.

Research at the University of Wisconsin-Madison School of Veterinary Medicine showed positive pressure tube ventilation can help get air between cows.  Additionally, if you don’t have sprinklers in the pens, wetting cows as they leave the parlor will promote evaporative cooling when they return to their pens, provided the pens have sufficient airflow.

Check if soakers are set up correctly.  It’s recommended that soakers turn on every 15 minutes at 68 degrees F and every five minutes at higher temperatures.  Position the soakers so the water overlaps a little and can soak the animals to the skin.  Let soakers run for one minute at lower temperatures and for one and a half minutes at higher temperatures.

Even the best managed farms see cows bunch together.  This can be from insufficient airflow, flies, sunlight or all the above.  The only thing we have seen to consistently reduce bunching is tunneling or cross-ventilating barns.

Water
Regardless of the season, water consumption remains important to maintain high milk production.  Under no heat stress, a cow will drink 30 gallons of water a day to produce 100 pounds of milk.  As temperatures rise above 80 degrees F, water consumption increases 2 gallons per day.

Make sure cows have at least 4 inches of linear water spacing, two waterers per pen and waterers located every 80 feet in a pen.  Another good practice is to give cows access to water in the return lanes.  Cows consume the most water after milking and this can help prevent congregating around waterers in the pens after milking.  Position return lane waterers so they won’t block cow flow.

Make sure water pressure is adequate to keep up with the cows and maintain adequate water supplies.  If it isn’t sufficient, you may have partially plugged water lines, insufficient water pressure or inadequate well capacity.

Heat stress can have a huge economic impact on the dairy.  Take the time now to assess your heat abatement strategies and make adjustments to limit any possible heat stress-related impacts.

This article was originally written for the March 25 issue of Hoard’s Dairyman.

About the author:  Dr. Darin Bremmer grew up on a farm in Shannon, Illinois. Af­ter high school, he attended the University of Wisconsin-Platteville and received a bachelor’s degree in animal science in 1993. From 1993 to 1995, he attended the University of Illinois and received a master’s in animal science with an em­phasis in ruminant nutrition. Bremmer then completed a Ph.D. in nutritional sciences with an emphasis in animal nutrition and a minor in dairy science from UW-Madison in De­cember 1999. In Dr. Grummer’s labora­tory at UW-Madison, Bremmer’s research focused on transition cows, studying ketosis and fatty liver. After completing his Ph.D., Bremmer worked for a major feed company as a dairy nutritionist and technical services manager in Wisconsin. In March 2003, he joined Vita Plus as part of the dairy nutrition and technical services team based in central Wisconsin.