Dr. Terry Mader

University of Nebraska

Northeast Research and Extension Center

Concord, NE

 Environmental management is an emerging area of interest in animal agriculture. It consists of modifying facilities or practices in order to minimize the effects of environmental stress on livestock. When implementing such practices, care must be taken that changes made to eliminate environmental stress during one season or period does not contribute to or result in increased stress occurring during another season.

For instance, during the winter windbreaks act as a barrier to reduce wind velocity and catch snow. However, during the summer, when wind (breeze) is critical for evaporative cooling, windbreaks can be detrimental to livestock. Studies at the University of Nebraska, Northeast Research and Extension Center, have shown that under normal environmental conditions, decreases in cattle performance during the summer, as a result of windbreak influence, were more than what was gained from the benefits of the windbreak during the winter.

Several reasons contribute to this. First of all, the degree of stress may be greater in the summer than in the winter; winter cold stress rarely results in death of feedlot cattle, whereas death loss due to summer heat is more prevalent. Secondly, cattle can and do use each other for wind protection in the winter; whereas, in the summer, the closer cattle are to each other (bunching) the more detrimental it can be.

In the summer, temperatures, humidity, and solar heat rise to levels that cause discomfort in feedlot finishing cattle. Providing shade is one method of reducing heat stress for feedlot cattle. Shades are defined as thermal radiation shields. Their chief function is to reduce heat load on the animal. They do not affect air temperature, but only reduce exposure to solar radiation. Major design considerations for shade structures are: orientation, space, height, and roof construction. The preferred orientation is east-west. This is recommended because a higher percentage of the shadow lies under the shade structure than when a north-south orientation is used. The shade structure should provide approximately 20-40 sq. ft. of floor space per feedlot animal recognizing that few production benefits will be realized I animals are overcrowded. Shade height should be in the range of 7 to 14 ft. keeping in mind that the higher the shade, the greater the air movement under the shade. To enhance natural ventilation in shade structures, the selected site should have minimal trees, other buildings, or obstructions within at least 50 feet of all sides. Various types of roofing materials can be used for shade structures. The most effective in terms of reducing heat load is a reflective roof such as white galvanized or aluminum. Slats or other shade materials with less than total shading capabilities are considerably less effective. Whether the benefits of shade justify the cost depends on year, condition of cattle, and possibly hair color of cattle.

Research conducted at the University of Nebraska has shown that cattle gains and efficiency are improved when shade is available, however, response is usually short-term with unshaded cattle compensating when weather cools. Cattle that were fed in areas that had windbreaks provided for winter protection benefited the most from shade. It may not always be economical to provide shade for cattle fed in more open areas where air movement is never restricted.

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