After a cooler and wetter-than-normal spring, summer heat is finally here. Temperatures are forecast to hit the mid-90s in Iowa beginning June 28, continuing through the weekend and into next week.
“With all the rain we’ve had recently, humidity will be elevated as well,” says Grant Dewell, Iowa State University Extension beef cattle veterinarian. “Feedlot cattle may not be acclimated to summer temperatures yet, and the fast warmup this weekend may cause some heat stress issues.”
Keep an eye on all cattle, especially feedlot cattle. “When temperatures heat up during summer, cattle feeders need to assess and manage the heat stress their feedlot cattle may experience,” notes Dewell. “Unlike pastured cattle that can seek shade and water and air movement to cool themselves, feedlot cattle have to cope with radiant heat from dirt or concrete surfaces. To reduce the risk to feedlot cattle, feedlot operators should have a plan for performance loss due to decreased efficiency and feed intake, in addition to a plan to prevent death due to heat.”
Keep close eye on cattle
Evaluate your cattle (especially feedlot cattle) each morning and again in the afternoon to see how they are handling the heat. Make sure cattle have access to plenty of fresh water and provide shade or sprinklers for them if possible. Pay close attention as the rapid change in temperature may catch some at-risk cattle (cattle at end of a feeding period, or cattle with previous respiratory disease) that are dealing with excessive heat stress.
“This week’s early heat event is a good opportunity to make sure your mitigation strategies will be functional for the rest of the summer,” says Dewell. The Iowa Beef Center website has information and details on proper heat abatement strategies such as shade and sprinklers.
To reduce the damage caused by heat stress, feedlots need to monitor temperatures throughout the summer. When the heat index is above 90 degrees, cattle will be under heat stress. In addition, hot weather following rain can dramatically increase the potential for a heat stress event. If overnight temperatures are above 70 degrees, cattle will have increased heat stress because of a retained heat load.
During times of increased heat stress, cattle should be observed closely to determine if additional strategies need to be implemented.
At temperatures above 80 degrees, cattle endure physiologic stress abating their heat load, says Dewell. Although cattle at this temperature are not at risk of dying, they will have an increased maintenance requirement to cope with the heat. Typically, pastured cattle are not as susceptible to heat stress as feedlot cattle, so this type of planning isn’t required for pastured cattle.
“Producers should evaluate feedlot cattle daily, especially during July and August, for evidence of heat stress,” he adds.
Check out additional resources
Heat Stress in Beef Cattle is a four-page publication by Dewell. Also, keep updated online with USDA ARS seven-day heat stress forecast. USDA has a smartphone app providing forecasts of weather conditions that can trigger heat stress in cattle. It’s a free from Google Play (Android) and App Store (Apple devices).