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Am J Physiol Regul Integr Comp Physiol 266: R1182-R1188, 1994;
0363-6119/94 $5.00
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AJP - Regulatory, Integrative and Comparative Physiology, Vol 266, Issue 4 1182-R1188, Copyright © 1994 by American Physiological Society

ARTICLES

Energy and protein requirements for molt in the king penguin Aptenodytes patagonicus

Y. Cherel, J. B. Charrassin and E. Challet
Centre d'Ecologie et de Physiologie Energetiques, Centre National de la Recherche Scientifique, Strasbourg, France.

Adult king penguins annually fast ashore for 1 mo for molting. By the end of molt, they have lost 44% of their prefasting body mass. About 18% of new feather synthesis occurs at sea, thus reducing both nutrient requirement and fasting duration. Plumage synthesis continues during the first 3 wk of fasting. Loss of old feathers occurs between day 12 and day 21 of the molt, and it is associated with a peak in daily body mass loss. The dry mass of epidermal structure synthesized during molt is 395 g. Body composition analysis indicates that fat oxidation accounts for 85% of total energy expenditure. The proportion for protein is 15%, a value twofold higher than during the breeding (nonmolting) fast. The mean energy expenditure is also 21% higher during the molting fast (3.04 W/kg). Compared with other birds, the energetic cost of feather synthesis is the lowest in king penguins (85 kJ/g) and consequently the energetic efficiency is the highest (25%). Changes in tissue composition during molt show that integument is the main lipid source (72% of the lipid loss) and thus the main source of energy (61% of the total energy expenditure). The integument and the pectoral muscles play a major role in molting protein metabolism, providing 20 and 57%, respectively, of the total protein needs for feather synthesis and/or energy expenditure. This result emphasizes the role of integument as a protein source, because the large premolting muscle hypertrophy is not sufficient to account for the totality of the protein cost of molt.


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