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First published online March 14, 2008
Journal of Experimental Biology 211, 1093-1101 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.010728

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The effect of food temperature on postprandial metabolism in albatrosses

H. Battam^1,*, M. A. Chappell² and W. A. Buttemer¹

¹ School of Biological Sciences, Institute for Conservation Biology, University of Wollongong, Wollongong, NSW 2522, Australia
² Department of Biological Sciences, University of California Riverside, Riverside, CA 92521, USA

^* Author for correspondence (e-mail: hb01{at}uow.edu.au)

Accepted 27 November 2007

Heat generated by the specific dynamic action (SDA) associated with feeding is known to substitute for the thermoregulatory costs of cold-exposed endotherms; however, the effectiveness of this depends on food temperature. When food is cooler than core body temperature, it is warmed by body heat and, consequently, imposes a thermoregulatory challenge to the animal. The degree to which this cost might be `paid' by SDA depends on the relative timing of food heating and the SDA response. We investigated this phenomenon in two genera of endotherms, Diomedea and Thalassarche albatrosses, by measuring postprandial metabolic rate following ingestion of food at body temperature (40°C) and cooler (0 and 20°C). This permitted us to estimate potential contributions to food warming by SDA-derived heat, and to observe the effect of cold food on metabolic rate. For meal sizes that were 20% of body mass, SDA was 4.22±0.37% of assimilated food energy, and potentially contributed 17.9±1.0% and 13.2±2.2% of the required heating energy of food at 0°C for Diomedea and Thalassarche albatrosses, respectively, and proportionately greater quantities at higher food temperatures. Cold food increased the rate at which postprandial metabolic rate increased to 3.2–4.5 times that associated with food ingested at body temperature. We also found that albatrosses generated heat in excess by more than 50% of the estimated thermostatic heating demand of cold food, a probable consequence of time delays in physiological responses to afferent signals.

Key words: specific dynamic action, postprandial metabolic rate, albatrosses, cold, food, thermoregulation