ABSTRACT
Full-fed beef animals have a very high tolerance for cold temperatures.[1-3] This is illustrated by the story of feeder cattle brought into a loafing barn for routine observations before noon one day, and later found to be strangely affected by some unknown condition. A virulent disease was feared and the animals were moved outside and isolated for observation, where they quickly recovered. The unknown condition was heat stress, and the stressful temperature was 0°C. The animals had become acclimated to − 30°C over the previous month, which demonstrates adaptability and acclimation. A second story involves more than 5000 cattle that died in northeastern Nebraska during a 1999 two-day heat wave.[4] When studying some of the affected feedyards seven days later, we found very few animals in distress, even though climatic conditions were more severe than the area had experienced during the heat wave. Again, adaptation and acclimation were factors. Both stories demonstrate a climatic stressor that may be more important than temperature alone: extreme variability of thermal conditions.
