It has been estimated that heat-related events in the Midwest have cost the cattle industry more than $75 million in the past 10 years. With summer temperatures rising, ranchers must be aware of how heat affects their cattle.
According to Deke Alkire, Ph.D., livestock consultant for The Samuel Roberts Noble Foundation, the ideal temperature range for beef cattle is between 41 and 77 degrees Fahrenheit. When temperatures exceed this, cattle are at risk of heat stress.
Environmental factors also play a role in the potential for heat stress including: relative humidity, wind speed, solar radiation, ground cover, access to water, diet, shade and nighttime temperatures. Additionally, individual animal characteristics will affect the potential for heat stress in cattle. Hide color, breed, health, adaptation, hair coat length and disposition all impact cattle’s susceptibility to heat stress.
Heat stress can lead to decreased milk production, calf growth, reproductive performance in cows and bulls, and stocker and feeder performance. There are several ways to identify and manage heat stress in cattle. “Fortunately, a lot of these signs are easy to recognize,” Alkire said. “The most obvious are cattle congregating in shady areas, standing in ponds, and decreased grazing activity.”
Other signs include increased water consumption, decreased weight gain and panting. According to the United States Department of Agriculture’s (USDA) Agricultural Research Service, more than 90 breaths per minute is an indication of heat stress, and a respiration rate of more than 110 indicates a dangerous heat stress level.
To prevent heat stress, Alkire suggested ranchers should make sure that during summer months and dry periods cattle have access to clean, fresh water and plenty of shade. If access to shade is limited, heat stress can be compounded by animals crowding together. Alkire advised against working and transporting cattle during periods of heat stress as well. If the cattle must be worked or moved to a new pasture, early in the morning is the best time, he said.
Since heat stress also can affect the reproductive performance of cows and bulls, ranchers should plan their breeding season around the hottest months, keeping in mind that heat stress can impact semen quality for up to eight weeks.
“Be prepared by planning now for heat stress,” Alkire said. “As hot weather approaches, monitor the Heat Stress Forecast developed by the USDA. This is a great tool for predicting the potential for heat stress in livestock because it takes into account wind speed, solar radiation, temperature and humidity to provide an accurate prediction for the region.”
Farmers and ranchers can access the Heat Stress Forecast at www.ars.usda.gov/Main/docs.htm?docid=17130.