Metabolizable energy requirements for maintenance and faecal and urinary losses of juvenile harp seals (<i>Phoca groenlandica</i>)

Abstract

Assimilation efficiency of energy in juvenile harp seals was 92.5–95.0% of gross energy intake when fed Atlantic herring and 72.2% when fed shrimp. Faecal energy losses increased directly with intake. Metabolizable energy (ME) ranged from 85.5 to 88.7% of gross energy intake for a diet of herring. Urinary energy losses increased directly with apparent digestible nitrogen intake. Faecal and urinary losses were not affected significantly by feeding frequency. Urine excretion indicated that feeding causes a diuresis, associated with increased energy, nitrogen, and ash excretion. A significant interaction was found for rate of weight change between feeding frequency and energy intake. Seals lost more weight at energy intakes below their maintenance level when fed four meals rather than two meals per day. Differences in rate of weight change with feeding frequency were not observed at other levels of energy intake. Maintenance energy requirements were estimated at 2658 kcal ME daily for seals fed two meals per day and 3514 kcal ME daily when fed four meals per day. Seals required approximately 3 times as much shrimp as herring of high lipid content to meet their energy requirements.