Meeting Abstract
P2.15 Friday, Jan. 4 The costs of a lazy summer – summer energy expenditure of Inuit sled dogs GERTH, N.; JACKSON, S.; STARCK, J.M.*; Univ. of Munich (LMU), Munich, Germany; Univ. Stellenbosch, South Africa; Univ. of Munich (LMU), Munich, Germany starck@uni-muenchen.de
Between summer and winter, Inuit sled dogs experience considerable changes in work load, temperature and food supply. In summer, the dogs are chained to the rocks, have no exercise, and experience mild temperatures (avg. +12°C), but low food supply (every 3�4 days). During winter they pull heavy loaded sledges, at low temperatures (avg. �25°C), but with more regular food supply. Temperature, exercise, and food supply affect the energy metabolism supposedly resulting in elevated sustained metabolic rate during winter. A comparison of resting metabolic rate (RMR) during summer and winter presents a test of the current paradigm in mammalian physiology that metabolic scope is constant within species; i.e., the combined loads of low temperature, high work load, and high food intake cause an increase of peak sustained metabolic rate and consequently elevated RMR. We used open flow respirometry to measure breath frequency, expiratory volume, VO2, VCO2 in 21 male dogs in Greenland (locations: Qeqertarsuaq 69°15�N 53°32�W, Qaanaaq 77°27�N 69°15�W). Summer conditions were: �resting and fasting�, and �resting 24h after feeding�. Winter conditions were: �resting at temp. > 0°C�, �resting at temp. < �10°C�, and �walking at temp. < �10°C�. Digestion after feeding during summer had a significant effect on all parameters. During winter, all parameters were significantly higher than summer fasting, but, were not different from 24h after feeding in summer, except walking. Summer-winter differences in RMR are most certainly minor, but clearly overridden by effects of continuous digestion because of regular food supply in winter. We suggest that the most demanding challenge during a lazy summer is intermittent feeding with repeated up- and down-regulation of digestive functions.
