While several factors including core body temperature, air temperature, humidity, 
air movement and solar radiation contribute to heat stress levels, with proper facility design and management, these factors can be better managed to improve cow comfort in a hot environment.

Depending on regional weather patterns, dairy producers may opt for one of two housing 
types -- drylots with shades or freestall barns.

If drylot housing is implemented, several design factors should be considered to lower the impact of environmental conditions on cows' heat load. Facilities should provide:

• 500 to 700 square feet per lactating cow
• 50 to 60 square feet of shade per cow near feed and water
• 50 to 100 percent of the feeding area with shade

With freestalls, several factors need to be considered. When designing freestall barns, orientation of the building is critical. Freestall barns should be on an east-west axis since buildings with a north-south axis have additional heat load from the sun on the west side in the afternoon. Buildings should be located at least 125 feet from tall structures to access the maximum wind exposure during hot months. For example, trees and silos can disrupt airflow for a distance of 5 to 10 times their height downwind. Providing a ridge opening of two inches for each 10 feet of building width is also important. Less critical areas should be located under the ridge to counter the effects of precipitation entering through the opening. Furthermore, continuous eave openings along both sides of the building should be at least half the size of the ridge opening, to open the buildings as fully as possible. Large sidewall openings may necessitate a roof overhang for shade and to some extent prevent precipitation from entering. Utilizing removable panels, wall sections or curtains will improve ventilation. Steeper sloped roofs provide better upward warm airflow because warm air rises, thus using 4/12 to 6/12 roof slopes are beneficial.

Since air flow movement is critical, producers should consider the following fan recommendations, keeping in mind specific recommendations vary by region:

• Place 36-inch fans every 20 feet and 48-inch fans every 30 feet
• Install fans 8 to 10 feet above the floor, high enough to avoid equipment
• Aim fans downward at about 30 degrees, pointing to a spot on the floor directly below the next fan
• Blow air on cows with a velocity of 5 to7 mph.

Investment Versus Benefit
With any dairy management improvements, producers must consider the benefits versus the investment and how it impacts performance of all other dairy systems. Partial budgets provide a good focus for the specific improvement in question, but oftentimes fail to tie back to the big picture. Therefore, partial budgets should be cautiously used for return on investment projections analysis.

The costs of supplemental fan cooling will vary greatly depending on the climate, types of barns and other cow cooling methods already in place. To determine the benefit to investment ratio, producers need to work through a series of questions to look at the opportunity expenses. Some questions to consider include:

• What is the difference in 150 day herd milk averages for winter and summer?
• What is the market price for milk?
• How much of the difference between winter and summer milk production do you want to recover?
• How many days per year are your cows heat stressed?
• How much less feed do your cows eat during the heat stress period?
• How much do your conception rates vary during the year?
• What are the expenses of the supplemental cooling, including fans, installation, depreciation, interest, electricity, and maintenance?

Properly planned systems cost $100 per cow and in specific areas producers have invested more than $700. As costs vary by region and operation, return on investment also does. For example, if cows in a specific herd were heat stressed for 100 days and investments in supplemental cooling could increase production over that period at an average rate of 10 pounds per cow, the gross return for a 1,000 cow herd would be $120,000. With costs of $100 per cow, the net return would be $20,000.

Economic benefits to reproduction and cow health are harder to project and have yet to be measured in a controlled setting. That's why it's important producers remember cow cooling systems have various components and the effectiveness of the systems or return on investment, is dependent upon all components of the system.

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