|Hahn, G - ARS COLLABORATOR|
Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: April 2, 2004
Publication Date: May 2, 2004
Citation: Nienaber, J.A., Hahn, G.L. 2004. Engineering and management practices to ameliorate livestock heat stress. In: Proceedings, International Symposium of the CIGR. New Trends in Farm Buildings, Lecture 6, 1-18. May 2-6, 2004, Evora, Portugal. 2004 CDROM Interpretive Summary: This article is a review of the impact of heat stress on swine, beef, and dairy animals. It is focused on recognizing the signs of weather conditions which are stressful, signs of animal distress, and management practices to reduce stress. Important weather variables include temperature, humidity, solar radiation, and wind speed. Distress signs include increased and labored breathing, lethargy of swine, reduced feed consumption, fighting or crowding near the water source, and shade seeking. Stress management practices include shade to reduce heat load, and animal wetting to increase heat loss by evaporation. Increasing air movement or elimination of obstructions to air flow are critical to animal well-being. Adjustments in feeding schedules and feed content have an impact on animal response and are discussed. However, care in managing feeding adjustments is very important to avoid increasing stress levels during refeeding or loss of tissue gain due to feed restriction.
Technical Abstract: Mature livestock are generally adaptable to a wide range of climate conditions. However, high environmental temperatures and lack of preconditioning to those temperatures can result in catastrophic losses of livestock in intensive production systems. The combination of elevated temperatures and humidity, little or no airflow, and no cloud cover or shade, especially if persistent three or more days without nighttime relief, can be stressful for livestock raised outdoors. Responses of livestock to these conditions include shade seeking, reluctance to leave the waterer, and increased respiration rate. Declines in feed intake occur as livestock strive to reduce heat load, and body surface wetting generally indicate an attempt to increase evaporative heat loss. Proactive management to ameliorate these conditions depends on the probability of occurrence and the economic feasibility of various management options. Stress management practices for open feedyards (both cattle and swine) include design considerations of prevailing air movement and wind obstructions, availability of water for drinking, wallows or sprinkling systems, and time of feeding. Shade structures require advanced planning (size, design and orientation), additional capital, and continual maintenance. Fully enclosed housing, while providing for greater control of the animal space and evaporative cooling, requires close attention to ventilation assurance. This paper is focused on the expected results or the impact of heat stress on livestock, recognizing the signs of heat stress exhibited in animal behavior or response, and the options to modify stressful conditions from open-unshaded feedyards to fully-enclosed housing of animals.