Energetics of fasting and subsequent growth in weaned harp seal pups, Phoca groenlandica

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Abstract
Changes in body weight and proximate composition were monitored throughout the postweaning fast in 20 male harp seal pups. Subsequent growth after the commencement of feeding was also examined. Weaned pups lost weight at a rate of 0.43 kg/day during the 1st week of fasting, declining to 0.20 kg/day by the 10th week. During the initial 2 weeks of the fast the lean body mass accounted for 39.8% of total energy losses (14.0% from core proteins and 25.8% from core lipids). The importance of core energy reserves later diminished until, by the 6th to 8th week of the fast, blubber supplied over 90% of the total energy. Core proteins were again mobilized during the final 2 weeks of the fast. Animals which started feeding after 1 to 2 weeks of fasting gained weight at a mean rate of 0.17 kg/day; those which started after 4 weeks of fasting gained at 0.29 kg/day. The relative amounts of muscle and fat deposited appeared to vary with the time (or physiological condition) when feeding commenced.