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Title: HEAT WAVES AND THEIR IMPACTS ON FEEDLOT CATTLE

Author
item HAHN, G
item MADER, TERRY - UNIV NEBRASKA NREC
item GAUGHAN, JOHN - UNIV QUEENSLAND
item HU, Q - UNIV NEBRASKA-LINCOLN
item Nienaber, John

Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: 8/9/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Hot weather can markedly reduce growth and efficiency of feedlot cattle. When hot weather persists for several days (often referred to as a heat wave), death losses sometimes occur. Ambient conditions which adversely affect the animals can be profiled by evaluating past heat waves. Using that approach, characteristics were developed for 6 categories of heat waves, ranging from mild to extreme. The characteristics and frequency of occurrence of heat waves in each category serve as a guide to the selection and operation of heat relief measures (e.g., shades, fans, sprinkling) appropriate for specific locations. This should provide a basis for improved environmental management of feedlot cattle in hot weather.

Technical Abstract: Persistent hot weather, often referred to as a heat wave, occurs periodically in many cattle-producing areas of the world. Such events can reduce production and efficiency, particularly in feedlot animals, and occasionally cause extensive death losses when the magnitude (intensity and duration) of heat loads is coupled with little opportunity for nighttime recovery. Retrospective analyses of heat waves resulting in death losses, in terms of Temperature Humidity Index (THI) conditions above or below selected thresholds, provide environmental profiles of conditions which put vulnerable animals at risk. Such analyses of 3 central United States heat waves are used here in conjunction with 43 yrs of summer weather records (1949-1991) for a representative location to develop descriptive characteristics for categorizing heat waves from slight to extreme, based on THI-hrs greater than or equal to 79 or greater than or equal to 84, and on hrs less than or equal to 72 for recovery. Most of the 42 heat waves a the representative locations were classified as slight, mild or moderate, but 10 were in the strong, severe, or extreme categories which can cause performance losses and possible mortality. Proactive counter-measures are discussed in the context of strategic and tactical actions to be considered for improved environmental management of feedlot cattle in hot weather. Provision for effective counter-measures (e.g., shades) should be considered as a form of insurance to reduce or prevent death losses during severe or extreme heat waves.