Help cattle beat the heat
By Dr. John Underwood

Whether you’ve got beef cows or dairy cows, these steps to managing heat stress will help your bottom line.

The summers of 2005 and 2006 were brutal on both man and beast. Temperatures in the 90s and 100s created havoc in keeping dairy and beef cattle healthy and productive. There were large decreases in milk yield, body weight and reproductive performance.

If you want to achieve optimum profitability, adopting good management practices for heat management is critical. You need to understand what a cow needs to handle heat stress.

In the Midwest, producers have to contend with both air temperature and humidity. Researchers have come up with a formula called the Temperature-Humidity Index (THI), which combines both air temperature and humidity into one number that better defines the actual environmental effect on the animal. For example, at 77 degrees with 50 percent humidity, the THI will be 72, and that number is considered to be mild stress on an animal.

There are THI tables that show ranges of temperatures and humidity and effectively show the level of stress on the animal. For a copy of a THI chart, you can contact your local MFA store. A chart will be sent to you.

When a cow is under heat stress, she will increase her rate of breathing, rate of sweating and blood flow to the skin. She will reduce blood flow to the uterus and udder. And dry-matter intake will drop. As a benchmark, remember that rectal body temperature is normally 101.5 degrees. Significant heat stress occurs when rectal temperature rises above 102.5 degrees.

Under low heat stress, the cow’s coping mechanisms easily compensate for the environment, but when the THI is in the 80s, the cow cannot cope and significant negative effects occur. That is when major intervention by the producer is needed.

The first provision needed is shade. Traditionally, trees provide significant shade—and that’s still the most common shade provider on many farms. When good shading or buildings are not available, artificial shading is called for. An effective form of shading is using shade cloths stretched over metal frames. The advantage of this shading compared to trees is the artificial shade can be moved just about anywhere to clean locations when the cattle contaminate one spot. This shading can be located closer to water sources, and it can be located in pastures that have inadequate trees for shading.

The second major provision is adequate water for drinking. A dairy cow can increase her water intake 29 percent or more when significant heat stress occurs. In both beef and dairy, having adequate water near the source of shade will help in keeping cows cooler—helping to minimize milk and body weight loss. Even a simple practice of hauling water to cattle in locations far from the normal water supply will yield major dividends on the hottest of days.

For dairy cows, it has become common to use water sprinklers and fans to keep cows cooler. If there are no covered feed bunks or free stalls to locate fans and misters, artificially cooling cows becomes more of a challenge. However, the use of sprinklers in the holding pen is a great alternative. With sprinklers, cows are confined in a small area; they are standing, and the concrete floor helps to drain off the water.

If a well-planned sprinkler system is put over the holding pen, cows can be put in it an hour or so before milking. It’s effective cooling, much like children running through sprinklers on hot summer days. If you cool cows this way often enough, the cows may begin visiting the holding pen for the benefits of getting cooled off.

With thinner margins on the way, cattle producers need to watch their investment. By working to aid the cattle in combating heat stress, producers ensure the animal will be better able to survive the heat and return to normal physiology. That’s one step toward overall profitability.

Dr. John Underwood is a dairy specialist for MFA Incorporated.

Click here to respond to an article