Israel Obadare, MS Graduate Student and Dr. Grazyne Tresoldi, Assistant Professor, Department of Animal Sciences, The Ohio State University
As the summer approaches, dairy producers across the US are once again reminded of the importance of taking proactive steps to keep their herds cool. Effective heat stress management is essential for maintaining good animal welfare and productivity. Research shows that the impact of heat stress can extend across generations - calves born to dry cows that had access to shade only (without active cooling) have shorter lifespans and produce up to 14.3 lb/day less milk as adults. Some studies even suggest that these effects may carry into subsequent generations.
Cows naturally produce a lot of body heat from digesting feed, moving around, and making milk. While they also lose heat to their surroundings, they can gain heat from it too. To stay cool, cows adjust their behaviour (Figure 1) and body functions - but when heat builds up faster than they can get rid of it, they become uncomfortable. This leads to higher, fever-like body temperatures, poor fertility, and lower milk production.
While it’s easy to spot cows in visible distress (Figure 2), subtle signs of heat stress are often missed. Research shows cows begin seeking shade at just 61°F and start using sprinklers (soakers) around 72°F - well before most of us would consider it hot. Picking up on these early cues is essential for timely intervention. Ideally, cows should breathe fewer than 60 times per minute and lie down for 9 to 12 hr/day.
The most effective and efficient cooling strategies combine shade (outdoors), fans, and soakers (Figure 3). But simply having these tools isn’t enough - how they are managed makes all the difference. Proper placement, timing, and maintenance are critical to maximizing cooling while conserving water and energy. Many US dairy farms already use fans and soakers, yet heat-related milk losses are still common, often due to inconsistent or suboptimal use. Research shows that, in the Midwest, a well-managed cooling system typically pays for itself in under three years. Calves, heifers, and dry cows also show better performance and welfare when kept cool. Prioritizing animal comfort is vital to meeting growing consumer expectations for ethical and sustainable dairy practices.
Fans and soakers should ideally be installed together over the feed bunk, where cows spend much of their standing time. Cows cool most effectively when their bodies are soaked first and then dried by moving air - this combination promotes efficient heat loss. It takes about 30 seconds of soaking at a flow rate of 0.9 to 1.4 gal/min to thoroughly wet a cow’s coat. Nozzles can be arranged to cover three cows at a time, with overlapping spray zones for full coverage. While using more water may improve cooling, it often leads to inefficiency. Using a short soaking cycle (30 seconds), followed by 4 to 5 minutes of fan-only time accomplishes effective cooling.
To maximize airflow, fans should face the direction of prevailing winds and be slightly tilted downward so that the moving air reaches cows’ backs, where cooling is most effective, at speeds of 8 to 10 ft/sec. Fan spacing and angle depend on fan size and type. For example: 48- to 55-inch panel or basket fans should be spaced every 24 to 30 feet, while 72-inch cyclone fans may be spaced every 40 to 60 feet. If you have extra fans, consider placing them in resting areas to increase airflow and encourage cows to lie down. Research shows that air speeds of at least 3.3 ft/sec, measured about 1.6 feet above the stall surface (the height of a lying cow), can significantly improve comfort during warm weather.
Cooling in holding areas is especially important. We’ve observed spikes in body temperature when fans and soakers are turned off during afternoon milking. For pasture-based dairy farms, consider using holding pens as designated cooling areas.
Don’t wait until cows are hot - start cooling early and use automated controllers. It’s much easier to prevent rising body temperatures than to cool cows down afterward. In Midwest climates, this means your system should begin running when the temperature-humidity index (THI) is between 65 and 68, roughly 70 to 75°F with moderate humidity. To avoid forgetting, ensure consistency, and reduce water waste, use automated controllers to turn fans and sprinklers on and off as needed. Make sure temperature and humidity sensors are placed where cows actually feel the heat, such as at cow height in the holding or resting areas - not near an office or breezy walkway.
Clean, fresh drinking water is equally important to all the strategies discussed above. Water intake increases during warm weather, so ensure access is easy and plentiful. Keep troughs clean, shaded when possible, and place them near resting, feeding, and exit areas to minimize walking distance.
Taking a few extra steps now can make a big difference all summer long. By fine-tuning your cooling strategies, you can improve animal welfare, boost productivity, and conserve water and energy.
Free Assessment
As part of our research, we’re offering a free, on-farm heat stress assessment to help you evaluate how your current cooling practices are performing, while also allowing us to benchmark the effectiveness of cooling strategies across Midwest dairy farms. Interested in participating? Visit https://go.osu.edu/awer_dairy, call (614) 292-5248 or email us to learn more!
Figure 1. Cows crowding under shade is a sign they’re warm. Increasing shade availability helps reduce their overall heat load. Pasture-based system in the Sacramento Valley, California (Source: G. Tresoldi).
Figure 2. Open-mouth panting is a clear sign that cows are struggling to cope with heat and likely have elevated body temperatures. Cross-ventilated barn in southeast Brazil (Source: G. Tresoldi).
Figure 3. The most effective and efficient cooling strategies combine shade, fans, and soakers. However, it's not just about having these tools—proper management is what truly makes them work. Free-stall system in the Central Valley, California
(Source: G. Tresoldi).
References:
https://doi.org/10.1186/s12711-021-00666-7
https://doi.org/10.3168/jds.2019-17351
https://doi.org/10.3168/jds.2020-18154
https://doi.org/10.3389/fanim.2024.1422937