Preparation is Key in Protecting Ruminant Livestock From Heat Stress

By Rachel Gibbs and Jake Galbreath

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 weekend, 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.

A Cattle Comfort Index forecast map is also available from the North Dakota Agricultural Weather Network (NDAWN) at https://ndawn.info/agriculture_cci.html. The forecast for June 21 shows potential for the southeast and south-central areas of the state to see areas of heat caution and heat danger. At these categories, producers can expect to see decreased production, reduced conception and possible deaths.

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 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.

During heat events, producers should be evaluating water sources regularly. Livestock whose sole source of water comes from tanks or troughs should be checked daily. If livestock have not had access to water for an extended period of time and then are allowed to drink ad libitum, this can result in fatal salt toxicity. In severe heat events, livestock without access to water for 24 hours or less can be at risk. If you suspect this has occurred, gradual rehydration is necessary to avoid potentially fatal brain swelling. Consult your veterinarian to determine a plan for gradual rehydration, which may take several days.