“Because animal welfare is their top priority, most livestock producers have protocols in place to address heat stress,” said Bill Brown, commissioner of the Kansas Department of Agriculture Animal Health . “Through proper management, cattle producers can reduce the serious impacts heat stress has on cattle.”
Life-threatening heat stress in cattle is usually not caused by elevated temperatures alone, but by a combination of high humidity and above-normal temperatures.
These primary factors can be made worse by secondary factors, such as multiple consecutive days of high temperatures, lack of nighttime cooling, lack of cloud cover, lack of wind, lack of shade or grazing endophyte-infested tall fescue pastures.
Signs of heat-related distress in cattle during hot, humid weather include:
• going off feed;
• standing in ponds or with their heads over the water tank;
• standing on the highest point in the pen or pasture trying to catch a breeze;
• panting, salivating and open-mouth breathing.
Panting scores are perhaps the best visual method to estimate the severity of heat stress on cattle. Breathing rates from 80 to 120 breaths per minute indicates moderate stress. A range of 120 to 160 breaths per minute indicates danger. More than 160 breaths per minute indicates that there is an emergency.
If signs of moderate heat stress are seen, producers may have a short time to provide a mechanism for cooling the cattle before the situation becomes life-threatening.
“Ready access to abundant cold water is essential during periods of heat stress,” said Larry Hollis, a veterinarian with Kansas State University Extension. “If water availability is limited, extra water tanks should be brought in so that dominant cattle cannot keep timid cattle away from the water.”
Hollis said access to shade is critical as well, especially for heavy feeder cattle or animals in an advanced stage of pregnancy.
Cattle should have the ability to move away from structures such as solid fences or barns that reduce air flow. Weeds around the edges of pens should be cut down to prevent their restricting air flow and also to reduce roosting places for flies.
Fly control should be used to keep cattle from bunching and further build up heat.
Sprinkler systems that provide large drops of cold water that will wet the cattle’s skin thoroughly can also be used, but will only increase the humidity problem if they do not wet the cattle’s skin thoroughly.
When sprinkled, cattle need to have adequate space to stand under the sprinklers as needed, and then move away to a dry area where evaporation will help cool their bodies.
Producers can request assistance from fire trucks from the local fire department if the situation becomes life threatening.
Livestock producers should postpone all gathering or handling procedures until after the critical heat period has passed.
If cattle must be worked during hot weather, producers should gather them into large holding pens with excessive space and watering capacity per animal the evening before.
During hot summer days, ranchers should begin working cattle so that all handling is completed no later than mid-morning. It is important to avoid crowding by bringing only a few animals to the chute at one time.
Cattle should be returned to open space, shade and water as soon as possible after working.
Producers should monitor radio, television and electronic media programs that regularly present weather and heat index information. When the heat index is high for people, it is also high for cattle.
Additionally, researchers at the University of Nebraska have developed a Temperature-Humidity Index that can help producers anticipate when heat stress will become a problem.
Producers should be on alert for heat stress problems when conditions reach an index score of 75. When the index reaches 79, the danger point has been reached. When the index reaches 84, emergency conditions exist.
If the heat index stays above 84 for three days in a row, death losses can start to occur, especially if there has been a slight breeze and the wind suddenly stops blowing or clouds that have been present suddenly dissipate.
Producers are encouraged to monitor the weather closely and use best management practices to minimize the effects of heat stress on cattle.
Heat stress forecasts produced as a partnership of USDA-ARS with National Oceanic & Atmospheric Administration National Weather Service are available at ars.usda.gov/Main/ docs.htm?docid=21351.