The ladies like it cool... starting today (part 1)

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On April 20 here in the Madison area, the temperature soared above 70 degrees for the first time in 190 days.  This was certainly a welcome relief and we are hoping for many more days like that since many of us were wondering if this severe winter would ever end. 

For 190 days, the last thing that dairy producers wanted to think about was heat stress abatement.  However, as we enjoy the warmer temperatures heading into May and June, we need to start thinking about our heat abatement strategies for our dairy cows.

For the most part, humans function best in warmer weather since our ideal thermoneutral zone is between 65 to 85 degrees.  For dairy cattle, it is a different story since they are cold-weather animals. 

Heat stress and its effect in dairy cows
Dairy cows function best in the thermoneutral zone of 25 to 65 degrees and certainly can do well in temperatures well below zero as long as management and facilities are in place to minimize wind chill.  In other words, cows can tolerate very cold temperatures and do quite well.  However, cows are dramatically affected once the temperature-humidity index (THI) goes above 75 degrees.  What may feel comfortable to us may actually be imposing heat stress in our dairy herds.  As the THI rises above 90 degrees, significant heat stress signs will be very noticeable and costly.

Decreased milk production is the most immediate and financially painful result of heat stress.  Cows simply eat less and, in combination with expending energy to keep cool, less milk is produced.  During severe heat stress, milk production can decrease as much as 25 percent. 

Increased mastitis rates may be another immediate effect of severe heat stress.  Heat stress effects just don’t end there.  We see residual heat stress effects well into October and November even though heat stress is not an issue.  Residual heat stress effects occurring in the fall season include low pregnancy rates, foot issues, poor fresh cow starts and body condition challenges. 

Obviously, these immediate and residual effects of summer heat stress can and will have a significant effect on the dairy’s cash flow and profitability if not correctly addressed.  It is important to review your heat abatement plan before the summer season and make the necessary changes.  A good method to review your heat abatement plan is the 3-M approach:  mechanical considerations, metabolic considerations and management considerations.

In this article, we’ll focus on the mechanical considerations and the things you can do now to prepare for warm temperatures.  Look for a future discussion on metabolic and management considerations.

Mechanical considerations
The three main areas that need to be considered for effective cow cooling include shade, airflow and water.  All three of these need to work in combination to provide the best result for your dairy operation.

Shade:  For best results, use solid shade for open lots, pastures and feed lanes.  For open lots and pastures, providing 40 to 45 square feet of solid shade per mature dairy cow is recommended.  The shade cloth should be at least 12 feet high.  Providing shade cloth over outdoor drive-by feed lanes is especially important for dry cows and pre-fresh cows in order to maintain dry matter intake.

Airflow:  The combination of water and fans is the most effective heat abatement strategy, so it is important to provide maximum ventilation and airflow along with an effective sprinkler system that will provide evaporative cooling.  Fans should start at 65 to 70 degrees and run continuously while providing 4- to 6-mph air speed over the cow beds and feed alley. 

If you cannot install both fans and sprinklers, choose sprinklers before fans.  Application of water with low pressure sprinklers cools cows more efficiently than fans alone.  Where water is used without fans, soaking frequency should be increased.   Prioritize the locations based on the cooling needs of the facility and the best return on your investment.  These locations should be considered in this order of priority:  holding pen, maternity pen, pre-fresh pens, lactating cows and hospital cows. 

The combination of properly placed fans and a sprinkler system is recommended for all of these locations.  The holding area is the most challenging environment in relation to heat stress as body temperatures will increase rapidly.  New research from the University of Wisconsin-Madison School of Veterinary Medicine has shown that positive pressure tube systems may be a viable option in holding pens to reduce the significant heat stress that occurs in this location. 

Water access:  Providing access to clean, fresh water is critical during heat stress.  Lactating cattle require between 25 and 35 gallons per day and water intake may increase as much 2 times that amount during periods of heat stress.  Availability of clean water to cows leaving the parlor is beneficial for increasing water intake during heat stress.  Provide 3 to 4 inches of linear water space per cow along with a minimum of two water locations per group.  Ideally, water should be available at every crossover between feeding and resting areas.  Check water flow rates during times of high water use and clean waterers regularly.

With milk prices at an all-time high, the payback for improved heat abatement strategies on your dairy is pretty significant.  Work with your consultant and other key industry leaders to evaluate your heat abatement program on your dairy.  There are a lot of resources and information for you to take advantage of in order to minimize the negative effects of heat stress.

About the author: Rod Martin is a dairy specialist and a member of the Vita Plus dairy technical services team.  He grew up on his family’s diversified livestock farm in southwest Wisconsin and attended the University of Wisconsin-Madison, where he earned a bachelor’s degree in agricultural education and animal science, and a master’s degree in animal nutrition.  He has 24 years of experience in consulting with Midwest dairy operations.


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