Heat danger reaches emergency levels

John Maday, Managing Editor, Drovers CattleNetwork | Updated: 07/21/2014
Drover's Cattle Network

For much of the country, this week has brought the first truly dangerous heat of the summer. As of late Monday, the USDA/NOAA forecast for Heat Stress in cattle projected “emergency” levels of heat and humidity across much of the middle of the country and parts of the Southwest for today, July 22.
The USDA/NOAA forecast maps for today show a huge area including most of Texas, Oklahoma, Kansas and parts of neighboring states rated at the emergency level, the most severe rating. Another pocket of emergency-level heat covers parts of southern California and Arizona. Heat rated at the “danger” level, one category down from emergency, extend across much of the eastern half of the United States. The forecast indicates the heat wave will reach its peak today and temperatures will moderate somewhat as the week progresses, but some areas of extreme heat will persist, particularly in Texas, Arizona and southern California.
At Iowa State University’s Veterinary Diagnostic and Production Animal Medicine website, Beef Extension Veterinarian Grant Dewell, DVM, MS, PhD, outlines precautions producers, and cattle feeders in particular, can take to minimize the effects of extreme heat on their cattle. Dewell reminds producers to work cattle early in the morning during hot weather, and not during the heat of the day or even in the evening after ambient temperatures drop. In cattle, core body temperature peaks two hours after the air temperature, and it takes them at least six hours to dissipate the heat load.
Dewell also offers suggestions and guidelines for drinking water, sprinkling pens, feeding times, potentially reducing the energy content of rations and other aspects of recognizing the signs and managing cattle at risk for heat stress. Read the full article from Dr. Dewell.
The Iowa Beef Center also provides a selection of heat-stress resources on its website. Among those resources is a summary of results of a survey researchers conducted following a deadly heat wave that killed over 3,700 head of cattle in Iowa during July 1995. The researchers conducted the survey to identify relationships between types of cattle and management practices and the impact of heat stress.
The survey involved 36 beef producers with 9,830 head of cattle on feed in 81 lots. Thirty-five lots with shade, averaging 24 square feet per head, reported an average death loss of 0.2 percent as compared to 46 lots without shade with losses of 4.8 percent. Producers reported higher death losses in dark-hided cattle versus light-hided, lots facing south or southwest versus those facing east or southeast and in heavier versus lighter animals. Lots containing heifers that were fed MGA had death loss averaging 3.8 percent versus 6.2 percent in lots with heifers not receiving MGA.