Dynamic response indicators of heat stress in shaded and non-shaded feedlot cattle. 2. Predictive relationships

Summer heat provides stressful conditions for Bos taurus feeder cattle; in extreme instances these conditions can be fatal. One management option is to provide shade structures for feedlot animals. This study was conducted during the summer of 2001 to compare physiological responses of cattle with shade access or noshade access. Eight steers were selected from a group of 12, and assigned individual pens. Four pens were fitted with shade structures that allowed the steers to choose shade; the remainder had no shade option. The animals were rotated through pen assignments during the summer season. Continuous measures of respiration rate and body temperature were recorded as response variables to the shade treatments. Environmental conditions were monitored for the experimental period. Daytime means and standard errors were 86.0 +or- 0.39 breaths min-1 for respiration rate shade, and were significantly lower (probability P