Digestive constraints on an aquatic carnivore: effects of feeding frequency and prey composition on harbor seals |
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Authors: | Email author" target="_blank">S?J?TrumbleEmail author P?S?Barboza M?A?Castellini |
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Institution: | (1) Institute of Marine Science, School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Fairbanks, AK 99775-1080, USA;(2) Institute of Arctic Biology and Department of Biology and Wildlife, Room 311 Irving I, University of Alaska Fairbanks, P.O. Box 757000, Fairbanks, AK 99775-7000, USA |
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Abstract: | We hypothesized that increased feeding frequency in captive harbor seals would increase nutrient loads and thus reduce retention time and the digestive efficiency of natural prey. We measured daily feed intake and excretion during 6 feeding trials and fed herring (49% lipid), pollock (22% lipid) or an equal mix of each diet over 24 months. Animals were accustomed to feeding at either high or low frequency. Body mass and intake did not vary with season. Although mean retention times were similar between diets and feeding frequencies, solute and particulate digesta markers separated at high feeding frequency. Consistent dry matter digestibility resulted in greater gut fill from pollock than from herring. Digestible energy intakes from pollock were approximately 25% greater than from either herring or the mixed diet. Lipid digestibility of herring declined from 90% to 50% when lipid intake exceeded 60 g kg–0.75 day–1. Our hypothesis of a trade-off between intake and digestion was not supported for protein but was supported for lipid. Results of this study imply that a flexible digestive system for harbor seals can compensate for ingesting prey of lower energy density by increasing gut fill and enhancing protein and lipid assimilation, to sustain digestible energy intake.Abbreviations DM
dry matter
- DEI
digestible energy intake
- DIT
diet-induced thermogenesis
- FF
feeding frequency
- MRT
mean retention time
Communicated by: G. Heldmaier |
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Keywords: | Digestibility Energy intake Feeding frequency Harbor seal Retention time |
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