Growing Beef Newsletter
May 2026, Volume 16, Issue 11
Preparing for heat stress with feeder cattle
Aimee Wertz-Lutz, IBC Director and ISU Extension feedlot specialist
On this beautiful spring day at the end of April, heat stress in cattle is far from mind, but Iowa summer is coming, and preparing ahead can lessen the impact of heat stress in feeder cattle. Meteorologists are predicting an El Niño weather pattern for the summer of 2026. This pattern is expected to bring a cooler and wetter summer than recent years. However, meteorologists also predict extreme heat periods for mid and late June, early and late July, and late August, which seems like most of the summer. I think it is safe to say that Iowa weather is anything but predictable, so preparing ahead is justified.
High demand for beef to meet the grilling-season needs occurs in the summer months. This demand results in many cattle reaching heavy market weights in the hottest months of the year. As a result, even brief periods of extreme heat can decrease feed intake and disrupt growth in feeder cattle. Heat stress also can result in a greater incidence of acidosis in feeder cattle, and if excessive enough, heat stress will result in death. Survey work conducted at Iowa State University after an extreme heat event in western Iowa reported that shade considerably decreased the number of cattle that succumbed to heat stress. The survey data also indicated that heavier cattle were more likely than lighter cattle to succumb to heat stress. In light of cattle currently being fed to heavier weights to meet market demand, the risk of challenges with heat stress is likely greater. An additional finding of this survey was that heifers fed MGA were less likely to succumb to heat stress than heifers that were not fed MGA. While death of cattle in extreme heat events often makes the news, cattle intake and growth often are compromised, and increased issues with subacute acidosis arise before any cattle succumb. As summer approaches, some key items to consider in preparation for heat events include 1) shade, 2) air flow, 3) sufficient water, 4) feeding strategy, and 5) management practices.
Shade. Shade protects cattle from direct sun exposure and keeps the ground cool, lessening radiant heat. Dark-hided cattle are impacted to a greater extent by direct sunlight than light-hided cattle, and ensuring that dark cattle have access to shade is critical.
Air Flow. Removing temporary wind breaks placed for winter, keeping vegetation surrounding the feedyard mowed, and considering within-pen mounding are all ways to improve airflow.
Water. Cattle water intakes are estimated to double during a heat stress event. It is important to make sure that there is sufficient space around water tanks or sufficient time in the day for cattle using automated waterers to consume the necessary amount of water, which may be in excess of 30 gallons per head per day for cattle approaching market weight. Providing additional water tanks during heat events may be necessary to ensure that cattle water requirements are met.
Diet and Feeding. Diet adjustments can be tricky. As the diet is fermented, heat is released. Peak heat of fermentation is released four to six hours after meal consumption. One consideration is feeding in the evening, allowing the greatest heat of fermentation to be released in the coolest part of the day. A second consideration is to include a source of fat in the diet. This maintains caloric intake but fat is not fermented in the rumen and therefore does not contribute to heat of fermentation. Other diet adjustments include using a buffer to offset decreased buffering capacity that occurs when cattle drool and saliva does not enter the rumen, or including an electrolyte package to balance those lost when cattle sweat. There also are commercially available feed additives that may mitigate symptoms of heat stress in cattle.
Management. Management such as handling cattle in the cool of the day, use of sprinklers when evaporative cooling is possible, or including MGA in heifers are other potential technologies that may benefit cattle feeding operations during heat stress events. Heat stress events can have rapid onset and being prepared to meet the need of cattle will lessen the negative impacts they have on cattle performance. Iowa Beef Center at Iowa State University has numerous resources for cattle producers to prepare for and mitigate the impact of heat stress in cattle. For greater detail and additional resources related to heat stress mitigation in beef cattle use this link.
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