Heat stress could become a problem for livestock because of a pocket of slow-moving hot air that is forecast for the upper Great Plains next week.
“The greatest impacts of heat stress come when cattle are exposed to a combination of elevated temperature and humidity over a period of time,” says North Dakota State University Extension Service beef cattle specialist Carl Dahlen. “Hot and humid conditions during the day can stress cattle, but cooler temperatures at night serve as a relief from the heat of the day.
“If forecast models are correct, daytime highs in the upper Great Plains will be in the mid-90s, with lows in the mid to upper 70s,” he adds. “These conditions present danger to cattle, and as we progress into the hottest part of the summer, a quick review of steps producers can take to manage and monitor conditions for heat stress is in order.”
NDSU Extension meteorologist Daryl Ritchison expects Wednesday and Thursday (July 20-21) to be the warmest days.
“With the high heat also will come high dew points, meaning it will be both hot and humid,” he says. “Heat indexes over 100 degrees may occur, especially on Wednesday and Thursday. The good news is that those extremes are only expected to last a couple of days, with other days more typical of this time of year, with maximums in the 80s.”
Being proactive is the best way to deal with heat stress in cattle, according to Gerald Stokka, NDSU Extension veterinarian. He recommends producers actively monitor temperature and humidity forecasts to anticipate when heat stress conditions will be developing.
“Once cattle are in a severe state of heat stress, you may be too late to help them,” Dahlen cautions. “Having a solid management plan in place to address heat stress could pay big dividends in the form of maintained animal performance during periods of heat and in avoiding death losses in severe cases.”
Heat stress occurs when cattle are not able to dissipate heat.
“Mammals have involuntary methods of regulating their internal body temperature, including shivering and sweating to maintain ‘homeostasis,’ or a constant, stable environment,” Stokka says. “Signs that animals are trying to maintain homeostasis include an increasing respiration rate, increased heart rate and increased panting. While animals are using extra energy, their feed intake declines.”
Dahlen and Stokka recommend producers take the following steps to protect cattle from heat stress:
- For pasture cattle, evaluate the condition of water supplies and ensure plenty of high-quality drinking water is available.
- 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.
- Know when to intervene. A combination of factors, including temperature and humidity, drives heat stress.
- Develop an action plan to deal with heat stress.
An action plan should include the following:
- Give each animal access to at least 2 inches of linear water trough space in a pen. This means that in a pen with 200 animals, you need to have 400 inches of linear water space. 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 to 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.
- 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.
- 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. The U.S. Department of Agriculture has a heat stress forecast tool available at http://www.ars.usda.gov/npa/marc/heatstress.
“Also, remember that interventions causing animals distress or to cool extremely rapidly could have disastrous consequences,” Stokka says.
Source: North Dakota State University