As I travel in our Southwest states, I quickly recognize heat stress is already starting to impact milk production.

Studies have indicated that the upper limit/critical temperature for heat stress will begin between 70˚F to 80˚F and can start as low as 68˚F for lactating dairy cattle.

Once temperatures exceed this range, cows will begin to combat heat stress by sweating, panting and decreasing their food intake.

The animal has to work harder and the energy costs to maintain that animal will rise. Some studies indicate that 35 percent more feed is needed just for maintenance.

As dry matter intake decreases due to stress, you will also see a decline in milk production. It is estimated that for every pound of peak milk production that is lost due to heat stress (15 to 30 pounds per cow per day during stress periods both acute and chronic), an additional 250 pounds of additional production will be lost over the entire lactation of that animal.

In addition to the effects on feed cost and the decline of milk production, your herd may also experience negative effects on immunity, metabolic health and, most importantly, significant negative effects on reproduction.

Studies indicate that acute heat stress, which is a short-term increase in the body temperature above 103˚F, or chronic heat stress, which is defined as prolonged exposure to the sun and heat over time, can result in a drop in conception rates by 25 to 40 percent. Studies indicate that an increase of just 0.9˚F in body temperature causes a decline in conception rates by 13 percent.

Loss of milk production is critical and affects the bottom line, but those detrimental effects of short-term and long-term heat stress on reproduction are even more significant. Add to that the fact that the highest-quality cows in your herd are the most susceptible to heat stress, and you’ll probably agree it is never too early to start planning to eliminate the heat stress concerns on your dairy.

The key point to consider in heat stress management is prevention. Although weather cannot be controlled, steps can be taken to control its effects. Visit with your fellow dairymen to learn first-hand what ventilation systems work in your area.

Look for a system that is effective in your market, whether it is tunnel ventilation, cross ventilation, fixed fan application, misters, feedline soakers or the new adjustable fan cooling system. Now is the time to take action to reduce or eliminate the negative impact of heat stress on your dairy.

The following are three areas of the dairy where ventilation systems are most beneficial.

1. Holding pen: Most cows spend 30 to 60 minutes in a holding pen several times a day. These holding pens are usually hot, humid, crowded and stressful for cows. The main objective is to make the conditions in the pen better with the use of air movement.

Mount fans on the holding pen ceiling at every 30 feet of length and each 15 feet of width. Angle the fans so that they blow the air onto the cows’ backs. It is recommended that the fans face the opposite direction from the milking parlor to prevent moving dust and humidity into the parlor.

Fans in the milking parlors are a good idea as well, just make sure to place the fans so that they blow air toward the holding pens; that way all fans blow air in the same direction.

2. Feedline: Feedline cooling is important because if you provide a comfortable place for the cows to eat, they will stay and eat! Shade the feedbunk and use fans to provide air movement as they eat. Cows are more likely to stay and eat in the shaded and ventilated area rather than stand in the hot sun to eat.

3. Freestalls: In operations with freestalls, cooling fans can be very effective. Although the facilities are naturally ventilated, it is important to understand that fans cool cows, not the building.

Because cows spend most of their time here, fans will prevent heat stress from affecting feed intake, ultimately affecting milk production. Remember, fans should be mounted to move air in the direction of any prevailing winds.

Remember that if cows leave a fan-cooled barn, enter a fan-cooled holding pen and milking parlor, then eat in a fan-cooled feedbunk, you have done quite a bit to eliminate heat stress on your dairy. 

James Kleinke is the V.P. of sales with Schaefer Ventilation and Equipment and grew up in southwest Minnesota working on his uncle’s farm and spent many of his weekends milking cows with his grandfather by hand in Nimrod, Minnesota.  EL

James Kleinke
V.P. of Sales, Schaefer Ventilation Equipment
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