Beat the Heat Before It's Late: Cooling Strategies for Dairy Cattle

Dr. Grazyne Tresoldi, Assistant Professor, Animal Welfare, Department of Animal Sciences, The Ohio State University

Feels like summer has already arrived in Ohio, and the National Weather Service has already predicted above-normal temperatures for this season. Moving recently from California to Ohio, I found it to be much warmer than expected, reminiscent of the sticky summers in Brazil. While I’m not a fan of comparing animals to humans, it’s important to remember that cattle start to feel warmer much earlier than we do and way before it hits the bulk tank. By focusing on the behavioral and physiological responses of dairy cattle, you can identify those animals experiencing high heat load early on. Coupled with the adoption of appropriate mitigation strategies, this proactive approach can help reduce losses and maintain cow comfort.

Cattle communicate discomfort through various behaviors. You may notice they shift their use of resources like lying in stalls, eat less, become more inactive, and exhibit higher respiration rates, often followed by panting, which starts with a simple drool string (Picture 1). To accurately assess this discomfort, it is important to measure these behaviors systematically for at least a few hours (about 6 hours) over a few days to capture weather variations. This simple assessment can highlight the strengths and weaknesses of your facilities, enabling you to make informed decisions. Don’t have the time? Don’t worry! I am preparing a team of students to help you with that!

The solution to mitigate high heat load is clear and consistent across climates: shade, soakers, and fans. During summer, cattle enjoy shade and avoid sunny areas during peak heat. Additionally, combining fans to increase convective heat loss with misters or soakers to promote evaporative cooling is the most effective way to cool cattle. For enhanced efficiency and effectiveness, it’s recommended to place both soakers and fans together at the feed line (Picture 2), as air removes more heat from a wet cow than a dry one.

Turning on soakers earlier helps cows keep cool from the start and is more efficient than trying to cool them down once body temperature has already risen. In temperate climates like Ohio, cattle start feeling hot usually when the air temperature is about 72°F or when the Temperature-Humidity Index (THI) is above 65. To ensure water is turned on and off only when needed by the animals, automated controllers help keep things consistent. These controllers should be placed in the barn to capture the weather conditions experienced by cattle.

Wetting cattle for 30 sec (enough to soak their coat) every 4 to 5 minutes and using fans that deliver a wind speed of 9 to 10 ft/sec (~3 m/sec) at the animal level is ideal. Higher flow rates result in larger droplets and more water sprayed per unit of time. While lower flow rate soakers (e.g., 0.4 gal/min) can abate heat, the fine droplets can drift to the bunk and affect feed quality. Therefore, using soakers that deliver larger droplets is preferred. Both 0.9 and 1.3 gal/min nozzles effectively cool cows, but using 1.3 gal/min has been shown to results in an extra 3 lb/day of milk per cow.

If your barn is not ready for this summer, the combination of the above items is also effective in waiting areas near the milking parlor. Research I have conducted in the past showed that a 45-minute cooling session reduced body temperature for 50 to 75 minutes, depending on the volume of water applied.

Cooling strategies for other categories of dairy cattle, such as calves, growing heifers, and dry cows, are less studied but still essential beyond providing shade alone and plenty of drinking water.

There is a misconception that calves are more resilient than other life stages; however, researchers have found that they are more sensitive to high heat load, even in temperate climates like ours. For calves housed outdoors, it's crucial to offer additional overhead shade and enhance airflow by elevating hutches or adding openings to improve air exchange (Pictures 3 and 4, respectively). In barn settings, mechanical ventilation systems like fans help facilitate air movement to aid calves in directly dissipating heat.

Dry cows are indeed more resilient than lactating ones; however, research has shown that combining sprinklers with forced air during the dry period can effectively reduce heat stress and improve the performance of fresh cows. Moreover, these interventions have demonstrated long-term benefits for the unborn offspring, including increased milk yield in their future lactations.

Would you like more information about something else? Send your questions my way at or through your county Extension educator. As a newcomer to Ohio (and the Midwest), I am eager to hear about your achievements and concerns. I would love to visit your dairy with a team of students to assess how your animals are coping this summer. Additionally, I am collaborating with a team of researchers, and we would love to hear more about your weather-related concerns and how they have been impacting your dairy farm.

 Picture 1. String drooling, as pictured, usually appears before other panting signs like open mouth and tongue out. For more details on how to assess panting you can visit: (Source: Grazyne Tresoldi)

 Picture 2. Fans and soakers placed together at the feed line are more efficient than either alone, reducing the need for excessive soaking overall. (Source: Grazyne Tresoldi)

A row of white plastic containersDescription automatically generated with medium confidencePicture 3. Calf hutch with a concrete block elevating its back. (Source: Moore et al., 2012)

 Picture 4. Calf hutch with adjustable ventilation at the back. (Source: Calf-Tel,