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heat stress

A map from Nebraska Mesonet shows the projected Cattle Comfort Index for Nebraska this week.

The July weather pattern is posing challenges for feedlot operators and cattle producers. Above- average rain fall across the state has created greater humidity and deteriorated pen conditions. The forecast calls for above-average temperatures, creating heat indexes that will reach critical heat stress emergency. 

When the forecast also includes little cloud cover and little or no wind, additional precautions are recommended. Producers should utilize empty pen space to allow cattle greater room and access to water. Supplemental water tanks may be needed to insure ample water intake to animals exhibiting signs of stress. Consider placing cattle in pens where cattle can be away from windbreaks to catch what little wind there is.

Several websites have more information about steps to take during heat episodes:

The Beef Quality Assurance website outlines steps to take during heat episodes: https://BQA.unl.edu/heat-stress-resources.

A recorded webinar from Dr. Terry Mader, UNL Professor Emeritus, provides great insight on heat stress and steps to take. It can be viewed at https://beef.unl.edu/webinar/heat-stress-mitigation-feedlot-cattle.

Additional steps may be considered. Work by Dr. Robbi Prichard of South Dakota State University has shown that manipulating the amount of feed delivered the day before the highest heat index will help cattle keep their internal temperatures lower.

Prichard explains: “By cutting the morning feeding by 25% we were able to keep cattle cooler in the hottest part of the day. The cattle recovered sooner and ate their feeding in the afternoon and had less heat load throughout the night.”

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“Why is this? The contributions of the heat of fermentation, digestion, and metabolism of the feed consumed in the morning become critical on the day that cattle hit the heat stress limit. If we take that feed away before cattle back away from feed we greatly improve the survival of the cattle.

“To do this, we watch the heat index forecasts closely. For example, cattle may seem fine today but if there is not enough night cooling (hours below 70 degrees F with wind) and the heat index will remain high the next day, one should consider taking away some of the morning feed delivery. This lowers the heat load midafternoon, which reduces the amount of heat that must be shed overnight,” Prichard said.

"We typically reduce the morning feed delivery by 25% today, and that may increase to a 50% reduction the morning of high heat index, depending on conditions and cattle status. If we wait for cattle to refuse feed it is too late. Afternoon deliveries are not adjusted. If the cattle can and do eat afternoon deliveries, that feed generates heat during the night when there are lower temperatures and less solar gain, lowering the total heat load accumulating in the body.

"It may seem like we are reducing DMI too much, but if we don't make these adjustments the feed refusals that will be coming in the days ahead will actually represent more pounds of feed than we are taking away with the feed call,” Pritchard said.

A move to higher roughage diets is not recommended, according to Pritchard. “Under normal conditions cattle will react to a diet change by increasing meal size and forage has proportionally higher heat of fermentation than concentrates,” he said. “Both of these factors will exacerbate the heat load problem. Staying with the current diet and controlling intake works best for us."

The Nebraska State Climate Office’s Nebraska Mesonet site calculates a cattle comfort index score. Stonie Cooper, Manager of the Nebraska Mesonet, reported that cattle comfort indexes were expected to reach close to a 120 this week in parts of the state. She said, “Precautions should be taken to provide additional care to not only cattle on feed but to all animals across the state.”

Additional information on heat stress can be found at https://Beef.UNL.edu .

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