Protect Cattle from Heat Stress

Extreme temperatures are expected to hit many parts of North Dakota this week, increasing the potential for heat stress in cattle, warns Karl Hoppe, North Dakota State University livestock systems specialist.

"One day of heat stress is uncomfortable, but two or more days back to back without night cooling can be deadly for livestock," says Hoppe.

"Signs that animals are trying to regulate their internal body temperature include an increased respiration rate, increased heart rate and increased panting," says Gerald Stokka, NDSU Extension veterinarian. "Once cattle start to pant, some heat stress has occurred."

"If cattle are already experiencing severe heat stress, it may be difficult to help them recover," cautions Zac Carlson, NDSU Extension beef cattle specialist. "Being prepared and implementing an action plan can minimize the impacts of heat stress on animal performance during the upcoming periods of heat and will avoid death losses in severe cases."

Hoppe, Stokka and Carlson recommend farmers and ranchers take the following steps to protect cattle from heat stress:

- For pasture cattle evaluate conditions of water supply and ensure plenty of high-quality drinking water is available.

- The amount of water livestock need depends on the type of animal and stage of production, with requirements often doubling during hot weather. The general estimates of daily water intake for beef cattle when the temperature is 90 F are as follows:

- Cows - 18 gallons for nursing calves; 15.3 gallons for bred dry cows and heifers

- Bulls - 20 gallons

- Growing cattle - 9.5 gallons for a 400-pound animal; 12.7 gallons for a 600-pound animal; 15 gallons for an 800-pound animal

- Finishing cattle - 14.3 gallons for a 600-pound animal; 17.4 gallons for an 800-pound animal; 20.6 gallons for a 1,000-pound animal; 24 gallons for a 1,200-pound animal

- Identify animals that are most susceptible to heat stress. They include feedlot animals closest to the market endpoint, very young and very old animals, and those with dark hides. Additionally adult cattle and yearlings that have experienced respiratory disease early in life or post weaning will be at greater risk.

- Be aware of the increased risk of "summer pneumonia" in suckling calves following heat stress. Early signs include calves off by themselves, a drooped ear, rapid respiration and dams with full udders. Consult your veterinarian for confirmation of the diagnosis and treatment options.

- Develop an action plan to deal with heat stress.

- Know when to intervene. A combination of factors, including temperature and humidity, drives heat stress.

An action plan should include the following:

- Give each animal access to at least 2 inches or more of linear water trough space in a pen. This means that in a pen with 200 animals, you need to have 400 inches (33 feet) of linear water space. More space is needed during times of heat stress as all of the cattle desire to be close to cool water. If your cattle have access to only small water troughs, add temporary space for additional water access during the summer.

- Evaluate your water supply lines and ensure you have sufficient water pressure and flow capacity to keep troughs full during times of peak water consumption.

- Move the animals' feeding time to late afternoon or evening. This will allow rumen fermentation to take place during the cooler night temperatures, and it will increase the cattle's lung capacity during the hotter daytime temperatures.

- If feeding once daily, consider moving feed delivery until the afternoon. 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.

- Provide adequate air movement. Remove unessential wind barriers (portable wind panels, equipment, weeds and other objects) to promote better air movement. Having mounds in pens gives cattle more elevation and possibly access to a microclimate with more wind.

- Cool the ground and the cattle gradually. Sprinklers cool the ground cattle are lying on as much as they cool the cattle. Set up sprinklers well in advance of anticipated heat stress because cattle take time to adapt to changes. Use the sprinklers during mildly hot days so cattle become accustomed to the sights, sounds and the cooling effects of the sprinklers. An alternative to sprinklers is running a hose into pens to wet the ground where cattle will be lying. Run the sprinklers or wet the ground before the day's peak temperatures.

- Be aware of the droplet size of water coming from the sprinklers. The goal is to have large droplets of water. A fine mist likely will make the pens even more humid and contribute to greater heat stress. When cattle are in severe heat stress, soaking the animal with water may be necessary for survival.

- Provide shade if possible.

- Add light-colored bedding (straw or corn stalks) to reduce the temperature of the ground on which cattle are lying. Apply bedding to the tops of mounds and other areas likely to have wind. Also, wet the bedding before or shortly after putting it out.

- Control flies as much as possible because hot cattle tend to bunch together and flies will add to the stress of hot days.

- Do not work cattle during temperature extremes. If working cattle is absolutely necessary, keep working time as short as possible, use calm-animal-handling techniques to minimize stress related to handling, and consider running smaller groups through the facility or into holding pens. Provide sufficient water in holding pens. Get started as early in the morning as daylight will allow. Do not work in the evening after a heat-stress day; cattle need this time to recover. Reconsider the necessity of working cattle during these periods; postpone or cancel some working events.

- Pay attention to long- and short-term weather forecasts and have a copy of the temperature-humidity index chart readily available. Determine the potential risk threshold and be prepared, even if the risk is several index units away.

"Also, remember that interventions causing animals distress or to cool extremely rapidly could have disastrous consequences," Stokka says.

The United States Department of Agriculture has a heat stress forecast tool available at: http://www.ars.usda.gov/plains-area/clay-center-ne/marc/docs/heat-stress/main/.

For more information from NDSU Extension, see publication AS1615 "Dealing with Heat Stress in Cattle" available at http://www.ndsu.edu/agriculture/ag-hub/publications/dealing-heat-stress-beef-cattle-operations.