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OSU Extension

College of Food, Agricultural, and Environmental Sciences

September 1, 2020 - 8:00am --

Summer will soon be replaced by fall, but it is difficult to say when that transition will take place here in Ohio. Even though September may begin to feel quite comfortable for us, dairy cows are most comfortable in temperatures between 40 and 60-degrees Fahrenheit. At roughly 70 degrees, cows may begin to experience heat stress.

I came across an acronym from University of Wisconsin-Madison regarding heat abatement: SAW. Shade, air, and water are the three focus areas. Cattle’s first goal is to find shade, even at the expense of airflow. If water and shade can be found together, that is where the cows will be.

It may seem funny to see cows huddled together on a hot day. “Don’t they know that it’s hotter standing side by side?”, we might think. However, this is the natural response of a herd animal under stress, even heat stress. Instinct says crowding equals stress relief. Group therapy, I suppose we would call it.

So, the goal of livestock managers, whether cows, sheep, goats, swine, or poultry, is to create a comfortable environment conducive for efficient and economic production. Knowing that livestock will gravitate toward shade means that bedding and feeding areas should provide some shade at minimum.

Mixing fans with sprinklers is perhaps the most effective cooling strategy. Avoid providing all the cooling measures in one specific location while neglecting another. Livestock should not have to choose between either the feed bunk or bedding area.

Sprinklers should produce large droplets and should be run only long enough to wet the top half of cows- not soak them. Timers and thermostats are often used to control these systems automatically. Once the cow is partially wet, airflow will do the rest of the cooling.

There is a difference between air movement and ventilation. Fans can create air movement that is helpful for cooling, but ventilation, or the exchange of air inside the facility with outside air, is often a process that happens unaided. This can mean either poor or excellent ventilation depending on the livestock facility. Newer structures are often designed with higher roofs that incorporate gables and side curtains to facilitate better air exchange. Lack of ventilation produces heat and humidity which promotes bacteria growth that can lead to pneumonia, mastitis, metritis, and other diseases.

Of course, there are many variations and set-ups that use these or other similar methods and may all work. The barn’s design and the management program play a role in how to implement heat abatement on each farm. Before spending the money or time installing or improving a system, consider visiting a neighbor or other farming friend who has a different system and discover what works well and what does not.

Drinking water is certainly the foundation of heat abatement. Ensure that water is supplied in sufficient quantity and that its quality is maintained as well. A dairy cow producing 80 pounds of milk a day may drink up to 80 gallons of water in the summer. 45 gallons are needed just to produce the milk while the other 35 is for cooling and basic body function and maintenance. A rule of thumb across all large livestock is 1 gallon of water for every 100 pounds of body weight. That may double in hot weather and also increases with lactation.  Annual water testing can reveal high levels of iron, heavy metals, salts, and other undesirable contaminants. Most labs can provide you with acceptable ranges of various substances. Some water quality issues must be corrected for milk licensing.

In dairy cattle, it is often noted that successful breeding declines during the summer months. This can often be attributed to the effects of heat stress. Cows and heifers are less likely to express estrus, or a standing heat, during hot summer days. They may become more active at night, making tail paint or other detection aids very beneficial as observable mounting occurs while most farmers are sleeping. Heat stress often makes maintaining pregnancy difficult for cows and heifers. Even if the embryo forms, it may be terminated early due to excessive stress on the mother. If using natural service, heat detection is not the issue, but keeping the bull cool certainly is. While the effects of heat stress on the bull may not take effect until 2-4 weeks later, the damage done may prevent him from successfully breeding cows for 6-12 weeks.

Keeping livestock well-watered and cool is humane and helps maintain productivity.


Matthew Nussbaum is an OSU Extension Agriculture and Natural Resources Program Assistant and may be reached at 330-264-8722.

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