Submitted By Rick Thomason

Being proactive is the best approach for dealing with heat stress in cattle. 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. Here are 3 steps you can take to help deal with heat stress in cattle.

Step one: Identify animals that are most susceptible to heat stress.
•Animals that are overweight have the least amount of lung capacity relative to body weight.
• Animals that are very young and very old also are at increased risk. They do not have the physiologic reserves to withstand prolonged periods of heat.
•Animals with dark hides are at a higher risk of suffering heat stress. Deaths of black-hided cattle on pasture without shade and limited supplies of water have been recorded. Research has shown that in cattle that were genetically closely related but had different hide colors, cattle with dark hides had a 2 F higher core body temperature than their cohorts with lighter-colored hide.

Step two: Develop an action plan for heat stress. The action plan is the essential actions you will take to protect the animals most susceptible to heat stress. The action plan
should include the following:
•Animals in heat stress need to drink water, so have plenty of it readily available. Cattle consume more water on hot days.
•Provide shade. Providing shade stops solar radiation from increasing body temperature. Cattle will congregate naturally under available shade.
•Air movement is an additional factor that promotes animal cooling. A breeze or wind moving over the hide of cattle promotes evaporative cooling.
•Control flies as much as possible because hot cattle tend to bunch together and flies only will add to the stress of
hot days.
•And maybe the most important, 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; some working events need to be postponed or canceled.

Step three: Know when to intervene.
•Heat stress is driven by a combination of factors. Temperature and humidity are two of the most frequently cited issues. A Livestock Weather Hazard Guide can be found at: https://www.noble.org/news/publications/ag-news-and-views/2009/june/monitor-and-manage-heat-stress/
•Understanding that heat stress in cattle is cumulative is important. If the evening temperatures do not cool low enough, cattle cannot fully recover physiologically before the next onset of heat. Cattle are at danger of death from heat exposure when the following occur:
•The heat index is 75 or greater for a 72 hour period
•The heat index during a 48 hour period is no lower than 79 during the day and no lower than 75 during the night
•The daytime heat index reaches 84 or higher for two consecutive days

Heat in summertime is not avoidable. However, you can take preventive measures before temperatures reach dangerous levels to minimize impacts of heat stress on cattle.

*Source: Dr. C.R. Dahlen, Beef Cattle Specialist & Dr. C.L. Stoltenow, Veterinarian; North Dakota State University