As we move into the hot months of summer, Iowa State University beef specialist Darrell Busby and engineering specialist Shawn Shouse offer advice on preventing heat stress in cattle. After a severe heat spell caused deaths in Iowa cattle during the summer of 1995, researchers surveyed producers to identify practices that kept losses to a minimum.

The first of these is providing adequate shade. During the 1995 heat spell, pens with shade had death loss only slightly above normal. Nonshaded cattle sustained higher death loss when they contained dark-hided or heavier cattle, or when the lot slope was facing west or south. Twenty square feet of shade per head, they say, is effective.

    
When asked about emergency measures, 89 percent of the producers indicated spraying with water was the most effective. Methods included fire trucks, water tanks with oscillating sprinklers or running water on the ground for cattle to stand in. Intermittent spraying provides evaporative cooling from the animal’s skin and can cool the ground surface by as much as 35 degrees. The specialists suggest using either shade or sprinklers, but not both, as the effects are not additive.

    
Monitor conditions closely during hot weather events. The specialists note that overnight lows greater than 74º F do not allow cattle to adequately cool overnight, requiring heightened monitoring and possible intervention the following day. Finally, they stress the need for timely feeding and plenty of water. The heat of digestion occurs four to six hours after feed consumption, so feeding cattle once per day in late afternoon reduces heat stress during daytime hours. Daily water intake increases to more than 20 gallons per head at 90º F.