Some aspects of thermoregulation in newborn reindeer calves (Rangifer tarandus tarandus)

• Published in: Acta Physiologica Scandinavica
• Main Authors: MARKUSSEN, K. A., ROGNMO, A., BLIX, A. S.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1985
• Subjects: Rangifer tarandus
• Online Access: http://dx.doi.org/10.1111/j.1748-1716.1985.tb07580.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1748-1716.1985.tb07580.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1748-1716.1985.tb07580.x

At birth reindeer calves often are exposed to sub‐zero ambient temperatures ( T a ) sometimes even combined with wind and precipitation. The resting metabolism was measured in three different age groups (1, 7 and 14 days old) at T a 's of –20, –5, 10 and 20 o C. Resting metabolism in the thermoneutral zone decreased from 5.1 W‐kg ‐1 at day 1 and 7 to 4.8 W‐kg ‐1 at day 14. At day 1 apparent lower critical temperature ( T Ic ) was 11 o C, while at day 7 it was 7.7 o C and at day 14 73 o C, but total body conductance continued to decrease below apparent T Ic . At T a of – 5 and – 20 o C total body conductance was: 0.77 and 0.72 W‐ o C ‐1 at day 1, 0.98 and 0.92 W o C ‐1 at day 7, r.08 and 0.91 W o C ‐1 at day 14, respectively. Thermal conductance of pelt samples from the trunk was determined in vitro at different combinations of windspeed, T a and wetness. The conductance of dry fur increased from 5.9 to 11.8 W‐m ‐2 ‐ o C ‐1 at a windspeed of o and 10 m s ‐1 , respectively, as compared to 28.7 Wm ‐2 o C ‐1 when wetted without wind. Newborn reindeer calves seem to be heavily dependant on non‐shivering thermogenesis in brown adipose tissue for their cold defence since deep body temperature in a calf subjected to propranolol infusion when exposed to a T a of – 25 o C in combination with a 10 m s ‐1 windspeed increased its cooling rate five times.