Technical Abstract: The focus of the MARC Environmental Stress Laboratory has been on effects of production facility management and the thermal environment on animal well-being, genetic potential, and nutrition factors. Effects of heat stress on beef cattle include adaptations of body temperature, respiration rate, heat production, and feed consumption as factors of thermoregulation. Heat stress has been shown to increase body temperature and respiration rate while decreasing feed consumption and heat production. These same response variables were evaluated using growing-finishing swine with similar results. Both species demonstrated increased heat production with increased heat stress if the animal is not adapted, representing an acute stressor. Shade, surface wetting of the hide, and increased airflow are potential stress relief practices that can be used; however, advanced planning is needed. Various mathematic models have been developed as management aids. Close observation of animals is important when heat stress conditions are in the forecast.