Heat stress in dairy cattle is one of the leading causes of decreased production in dairy herds.
According to the University of Missouri Extension, some heat stress is unavoidable, but effects can be minimized if certain management practices are followed. Steps to reduce heat stress are especially important for those operations that utilize freestall systems for their herds.
When can heat stress begin
Because cattle sweat at only 10 percent of the human rate, according to the Extension, they are more susceptible to heat stress.
The ideal temperature range for dairy cattle is between 25 and 65 degrees. Once the temperature goes above 80 degrees, cattle reduce feed intake, which has a negative impact on production. At 90 degrees or above, producers can usually notice a dramatic decrease in milk production ranging from 3 to 20 percent.
Humidity also plays a significant part in heat stress. There are three temperature-humidity ranges of concern. A temperature of 100 degrees and 20 percent humidity is the range in which producers should begin serious measures to ease the stress on the cattle. Some type of cooling should be started. The danger occurs as the temperature nears 100 degrees and 50 percent humidity. The lethal range for cattle is 100 degrees and 80 percent humidity.
Reducing the temperature
Dairy cattle need mechanical means to reduce heat, such as body sprinkling, to aid in evaporation and effective air movement systems to aid in cooling.
When the temperature reaches danger levels, add additional sources of water near the feeding area. Another way to increase water consumption is to make certain water is cool.
While there are several ways to help reduce the temperature for cows, having more water available for animals is critical.
Increasing air flow is another important component. MU Extension recommends that producers insure air moves freely in all sections of the barn. That can be accomplished by the installation of fans or by opening the sides the barn, if possible.
If cattle are outside during the summer, producers should provide shade, be it trees or a man-made structure. Providing shade over the feeding area will also increase feed intake.
Misters are another addition that can reduce heat stress.
There are several items to consider when installing them. Be certain misters are over a clean, preferably concreted, area, so animals do not lay down on mud or other areas causing an increase in mastitis, and misters should not be left on continually. According to the Extension, if water is dripping from the udder, then reduce the time misters are on. If misters are placed near the feed bunk, be certain the feed does not become wet – wet feed will mold faster during hot weather.
At the University of Nebraska, research was conducted to study the feeding frequency of cattle from 8 a.m. to 8 p.m. with and without supplemental cooling. Results showed cattle shaded and cooled by sprinklers near the feed bunks ate between 63 to 100 percent of the time as compared to uncooled cattle. Therefore, offering a cool, shaded area for feeding during daylight hours will increase feed intake, thereby helping to maintain production.
