By Howard Blalock, Ph.D.
A producer survey conducted by Busby and Loy (A.S. Leaflet R1348) reported that the heat event in 1995, resulted in the death of 3750 head of cattle due to high temperatures, high humidity, and no wind across 13 west-central Iowa counties. Total production losses were estimated at $28 million. Heat stress is a function of temperature, humidity and wind speed with other factors also contributing such as color and weight. Moderate heat stress potential exists at temperatures above 80 F with the potential for severe heat stress above 90 F. Heat stress may reduce feed intake, reduce average daily gain and potentially result in animal death. Even though it may not be possible to prevent all effects of heat, there are some ways to reduce them.
Water and Water Quality– An adequate supply of clean, fresh water is essential for optimal health and growth of cattle at all times, with even greater importance during periods of heat stress. Cattle can drink greater than 20 gallons of water during times of severe heat. Making sure waterers are kept clean with adequate space and flow to accommodate the cattle is essential. Poor water quality may reduce consumption or lead to other issues that may complicate the animals’ ability to cope with heat stress. If water quality is questionable, it may be necessary to provide an alternate source of water to the cattle in times of extreme heat.
Sprinklers, Shade, and Airflow –Using sprinklers and/or shade structures can be effective strategies to combat heat stress. Shade structures can significantly decrease feedlot surface temperature. The University of Nebraska has demonstrated improved performance and efficiency by providing shade to feedlot cattle. The use of sprinklers has also been demonstrated to improve efficiency by as much as 5% in feedlot cattle. It is best to utilize a sprinkler with large droplets of water instead a mist to facilitate efficient wetting of the cattle while minimizing the impact on the humidity in the pen. Overuse of sprinkler systems may increase the humidity at the pen surface and reduce the effectiveness of heat transfer through evaporation. Sprinklers should be utilized to wet cattle in as short of time as possible, preferably during the morning or evening. Adequate air flow is important in the success of either method but is essential if using sprinklers. Airflow is perhaps the most important factor in managing heat stress and should be considered as part of any heat management plan.
Feeding Schedules – Altering the time of feeding is another method which may aid in combating the effects of heat stress. During times of severe heat, feeding cattle either the entire ration or the majority in the afternoon decreases water consumption and improves efficiency by up to 2%. The reported effect is thought to occur by a reduction in the metabolic heat load during the hottest portion of the day. Good bunk management and providing a highly palatable ration is important, especially during stressful events.
Feed Additives –There are feed additives on the market that may offer some benefit to cattle during times of heat stress. Yeast extract products have been shown beneficial during heat stress as well as others. Capsicum extract has been used in several areas to manage heat stress with many producers reporting positive benefits. There isn’t a lot of data defining Capsicum’s direct effect during periods of heat stress. There is data that suggests capsicum may change the eating behavior of cattle so they consume less feed per meal but consume more meals per day. This should positively impact the metabolic heat load so that less heat would need to be dissipated per meal.
Research examining methods to reduce the effects of heat stress indicate cattle may experience compensatory gain as the severe heat relinquishes, however, cattle must survive the episode to have the opportunity. A heat stress management plan is vital to any feedlot. For more information, please contact your local QLF District Sales Manager.