Submitted to: Livestock Environment International Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: March 12, 2001
Publication Date: N/A
Interpretive Summary: Heat waves are periods of high temperature, high humidity, low wind speed and little cloud cover. This combination of weather conditions has caused severe death losses of feedlot cattle throughout the midwestern part of the U.S. This paper describes two experiments designed to better understand how cattle respond to heat waves, and how producers can prepare for them. The first study presents information on how animals adjust feed intake during simulated heat waves within environmental chambers. The second study presents results of an environmental chamber study that used reduced feed intake to reduce stress response. The result was different from expectations and could have increased rather than reduced stress. These reports demonstrate the importance of feed intake as a heat wave response.
Technical Abstract: Two experiments were conducted in the U.S. MARC Environmental Laboratory chambers using finishing beef cattle subjected to simulated heat waves or a cyclic heat stress pattern. Measurements included daily feed intake, number of meals, and tympanic temperature. Results clearly illustrated the dynamics of feed intake in response to environmental temperature and the close correlation between tympanic temperature and patterns of eating. When feed was partially restricted just prior to heat stress, there were no effects on the average tympanic temperature, feed intake, or number of meals measured over the duration of the heat stress. However, there was a one-day increase in feed intake at the beginning of heat stress which may be counter-productive under feedlot conditions.