Protect Ruminant Livestock From Heat Stress

Proactive management of livestock prior to and during heat events is critical in protecting livestock from heat stress.

North Dakota State University Extension livestock specialists encourage livestock owners to monitor weather forecasts and anticipate when conditions may pose a significant risk to livestock. Such conditions exist when above-average temperatures collide with increased humidity. These conditions are expected to hit many parts of North Dakota this week, with many cities experiencing temperatures 5 to 10 degrees Fahrenheit higher than reported averages for this time of year.

A temperature-humidity index chart can help ranchers identify when livestock are most at risk for developing heat stress. Livestock begin to experience moderate heat stress at a temperature humidity index of 82 to 83, severe heat stress at 84 to 86, and extreme heat stress at 87 or greater. A temperature-humidity index chart can be found at ndsu.ag/heat-stress.

Heat stress can significantly impact animal performance, health and welfare, making it critical to prepare a proactive management plan for unavoidable heat events. Heat stress occurs when an animal's cumulative heat load outweighs the animal's ability to dissipate heat, causing body temperature to rise.

NDSU Extension livestock specialists recommend several heat event action plans:

Access to quality water sources

Water availability and quality are essential to managing heat stress in livestock. Each animal should have at least 2 inches of linear water trough access. For example, a pen with 200 animals should have 400 inches of linear water space. Evaluating your water supply lines and ensuring sufficient water pressure and flow capacity to keep troughs full during peak water consumption is also important. The amount of water livestock need depends on the animal type and production stage, with requirements often doubling during heat events. Specific water requirements for livestock can be found at ndsu.ag/livestock-water.

Shade infrastructure and fly control

Livestock owners should consider placing temporary or permanent shade structures for livestock in confinement operations or open pastures with little to no tree cover. Each animal should have a minimum of 20 feet of shade space (10 feet for small ruminants) to prevent animal grouping and comingling of sick animals. Spraying for flies prior to a heat event will also be a vital step in reducing animal grouping. Importantly, shade structures should not impede air movement, and wind barriers should be removed to promote better air movement. Livestock in confinement benefit from mounds that provide elevated wind access.

Surface cooling strategies

Proactive management of pen surface temperature can be an effective way to reduce the risk of heat stress. These strategies include dampening the pen with water or adding light-colored bedding (straw or corn stalks) to reduce the temperature of the ground. Sprinkler systems are a popular way to cool ground temperatures in confinement cattle operations. This strategy should be implemented well before a heat event and before peak heat on high-temperature days. Large water droplet size is important to avoid increasing humidity.

Animal handling

Any type of livestock handling, processing or transportation should be avoided during heat events as much as possible. If working with livestock is absolutely necessary, livestock handling should be limited to the early morning hours (prior to 10 a.m.). Calm animal handling techniques will be important to minimize stress related to handling, and livestock owners should consider working with smaller groups of livestock at a time to prevent crowded facilities. Working facilities, including holding pens, should have ample access to water, and personnel should be dedicated to monitoring livestock stress status. Avoid working livestock in the evenings during a heat event to give livestock time to recover and cool down during cooler periods of the day.

Adjusting feed intake timelines

Livestock owners should consider moving livestock feeding time to late afternoon or evening. This will allow rumen fermentation to occur during cooler night temperatures and increase the animal lung capacity during hotter daytime temperatures. If feeding multiple times daily, consider feeding a small meal in the morning and a larger portion of the diet later in the afternoon. Decrease the amount of feed offerings during and for several days after heat stress to allow animals ample opportunity to recover.

Know when to intervene

Livestock suffering from heat stress will exhibit several signs of distress as their body works to return to homeostasis. Ruminant livestock, including sheep and cattle experiencing extreme heat stress, will exhibit increased respiration rate and panting score, foaming around the mouth, down head, and lethargic appearance. Livestock owners should keep in contact with their local veterinarian and contact them immediately if they have animals in severe distress. Animals should be gradually cooled by moving to nearby shaded areas with ample air movement. Rapid cooling (such as spraying with cold water) can have severe consequences for livestock in severe distress.

The U.S. Department of Agriculture has a heat stress forecast tool available at https://www.ars.usda.gov/plains-area/clay-center-ne/marc/documents/heat-stress/main/.

For more information on dealing with heat stress in cattle, see the NDSU Extension publication, "Dealing with Heat Stress in Beef Cattle," at ndsu.ag/heat-stress.

For more information on dealing with heat stress in small ruminants, see "Heat Stress in Small Ruminants" from South Dakota State University Extension at https://extension.sdstate.edu/heat-stress-small-ruminants and "Managing Heat Stress in Sheep and Goats" from Nebraska Extension at https://extensionpubs.unl.edu/publication/g2355/2023/html/view.