The next few days will bring this season’s first significant heat wave. I’d like to remind us of the impact that heat and humidity can have on our livestock; and our responsibility as livestock caretakers to minimize the health risks to our livestock. In severe cases, livestock can die. Much more commonly, the livestock are stressed and we see reductions in performance
Understanding Heat Stress
Heat stress occurs when an animal experiences more heat than what they can get rid of. Normally, an animal gets rid of excess heat through respiration and panting. Unlike humans, livestock also have very limited ability to sweat. In fact, pigs do not have the ability to sweat at all. Animals that gain excess heat during the day attempt to dissipate that extra heat at night. That is why multiple hot days with hot, humid nights are potentially so dangerous for our livestock.
We have all heard the phrase – “it’s not the heat, it’s the humidity”. This is quite true for livestock as well. The livestock industry has developed what is called the Temperature Humidity Index or THI that combines both air temperature and relative humidity to assess heat stress risk for various livestock. The chart above quickly allows you to assess the level of risk for your animals. Another great resource is the USDA Livestock Heat Stress Forecasts, which can be found at: https://www.ars.usda.gov/plains-area/clay-center-ne/marc/documents/heat-stress/main/. This website forecasts a week ahead giving you time to plan how to minimize the risk of heat stress.
Managing for Heat Stress
Heat stress prevention and management centers around a few key areas: water, shade, and environment & stress management.
Water: Livestock will want to drink significantly more water when they are hot. It is important to keep the water temperature below 80o. Keep your water tanks clean; and make sure there is enough water so all animals can drink as much as they want. This may mean an additional tank or placement closer to the animals on pasture.
Shade: Animals, especially dark colored animals, heat up when they are in the sun. Providing shade reduces this radiant heat load directly on the animal as well as reducing soil temperatures beneath them. Take advantage of natural shade in the pastures or if necessary utilize buildings during the daytime. If you are using buildings, make sure there is plenty of air movement and ventilation. You can check this by being in the building yourself – it should feel cooler to you too. If not, adjustments need to be made.
Environment and Stress Management: Avoid any additional stress on the livestock during hot and humid periods. Time any working or movement of the livestock to the coolest part of the day, typically in the morning before 9 am. Consider postponing management tasks such as vaccinating until the ‘heat wave’ breaks. Other management tips include having implemented an effective fly control program. If you can set up a sprinkler system that provides effective evaporative cooling ahead of the “heat wave” and have the cattle already accustomed to it will provide you another tool. It’s important to do this correctly to avoid creating an increased zone of humidity.
With regular observation and planning, you can minimize the risk of heat stress on your animals. One final tip – observe your animal’s breathing rate early in the morning. If it’s faster than normal, your animals did not dissipate all their extra body heat in the night; signaling to you that you may need to find another way to help your livestock remain cool.