Dairy Excel: Keeping your dairy cows cool


Hot weather management for dairy cows has been generally a topic of discussion in areas of the U.S. that experience consistent hot summers like the Southeast and Southwest.

However, more recently producers here in the Midwest and Northeast are taking a look at ways to reduce heat stress on cows.

Times have changed.

Why has it become a more important management choice to now cool cows here in Ohio when 10 years ago we talked very little about it?

Well, one of the major differences is the production level of today’s cows. It is becoming more common to have herds averaging over 70 pounds of milk per day and these cows generate a lot of body heat and subsequent heat stress.

Today we have had much more research indicating the effects of heat stress on milk production. We also have current research to show the most effective way of cooling cows in today’s freestall barns.

Recent projects.

At the Western Dairy Management Conference this year, Dr. Brouk and Dr. Smith, from Kansas State, reported on two research projects dealing with heat stress abatement in four row freestall barns.

In the first study, three different methods of cooling cows were compared with 93 Holstein cows in a four row freestall barn.

Treatment No. 1 had a double row of fans 36-inch diameter mounted every 24 feet over the freestalls.

Treatment No. 2 had a row of fans 36-inch diameter over the freestalls and another row over the feed lane.

Treatment No. 3 had a double row of fans over the freestalls, and another row over the feed lane.

Fans and sprinklers.

All the fans had a delivery rate of 10,000-11,500 CFM and were angled down at 30 degrees. Each pen was also equipped with similar sprinkler systems consisting of 2.5 gph nozzles spaced every 78 inches on center at a height of 8 feet above the headlocks.

Sprinklers were activated when temperature was above 75 percent on a 15-minute cycle with three minutes on and 12 minutes off.

The results of the three treatments for dry matter intake and milk production were:

Treatments      DMI lbs.      Average

            milk lbs.

      Treatment 1      55.6      93.3

      Treatment 2      56.2      98.8

      Treatment 3      56.3      96.5

Dry mater intakes were similar across treatments, however, the cows in treatments 2 and 3 produced more milk.


This would suggest that the cows in group 1 utilized more energy to expel heat, which reduced the amount available for milk production.

A second study in 2000 compared the use of fans over freestalls and feed lane vs. fans only over the feed lane.

Fan treatments were 36-inch fans mounted every 24 feet on the feed lane or 36-inch fans every 24 feet on the feed land and over the center of head-to-head freestalls.

All pens were equipped with sprinklers operating as in the first trial. Cows exposed to the treatment with fans over both the feed lane and the free stalls produced more milk – 85.6 pounds per day vs. 79.8 pounds per day for the cows exposed to fans only over the feed lane.

Pen feed intakes were greater for the cows being cooled by fans over the freestalls and feed lane – 54 vs. 52.7 pounds of dry matter per day and the respiration rates for the cows receiving more cooling were lower at all times of the day.

What it all means.

The results of both studies clearly demonstrate that in a four-row freestall barn, greater milk production and lower respiration rates can be obtained by locating fans on both the feed lane and over the freestalls.

Two rows of fans are not needed over the freestall that are head-to-head. If 36-inch fans are utilized they should be located no more than 30 feet apart.

If 48-inch fans are used, they should be located no more than 40 feet apart. All fans should operate when temperature reaches 70 degrees and sprinklers should operate when temperatures exceed 75 degrees.

Three-step process.

In summary, the researchers say effective freestall barn cooling is comprised of three steps.

First, enhance the natural ventilation of barns. For new barns this means orientation that is east to west to reduce solar radiation, high sidewalls and open ridges.

For some of our older structures this may mean removing some siding and opening ridges.

Second, provide adequate water space and volume. Current recommendations suggest 3-4 linear inches of water space for every cow.

Water should be placed at each crossover. In six-row barns or if considerable over-crowding exists, more water pace may be needed. Water located at an exit of the parlor is also a recommended practice.

Thirdly, utilize effective supplemental cooling systems which are cost effective. Using sprinklers and fans together provides for maximum cooling. Do not use water without fans.

You will have to decide what cooling system fits your operation. If you have limited resources and have no cooling yet on the farm, start first with the holding pen at the milking parlor.

This is especially important if cows are spending over one hour each milking in the holding pen. Include rows of 36 or 48-inch fans placed at a 30 degree down angle every 30 to 40 feet of holding pen length blowing from the parlor towards the cows.

Opening up the holding pen as much as possible is also recommended. Finally, there are a few adjustments one could make in the feeding program that can help reduce heat stress.

Feed at the cooler time of day, push-up feed more often, feed two times instead of once per day and keep feed bunks clean.

Your nutritionists could also make some ration formulation changes that can help reduce body heat from rumen fermentation.

Hot weather is the time of year to feed the highest quality forage available. The key to maintaining production in hot weather is to keep the cows eating.

(The author is a dairy agent for OSU Extension in Wayne County. Questions or comments can be sent in care of Farm and Dairy, P.O. Box 38, Salem, OH 44460.)


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