Milk composition in the Weddell seal Leptonychotes weddellii

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TitleMilk composition in the Weddell seal Leptonychotes weddellii: Evidence for a functional role of milk carbohydrates in pinnipedsAbstractWe propose that secretion of milk sugar has important consequences for the metabolic economies of lactating phocid seals and their pups. Milk was collected from 21 Weddell seals Leptonychotes weddellii in McMurdo Sound, Antarctica, and assayed by standard methods. Milk composition changed over the course of lactation, but at mid- to late lactation (16-40 d postpartum),Weddell seal milk composition was relatively constant at water, 33.8 +- 0.82% 54.0% +-0.80% fat, 10.1% +- 0.16% crude protein, 0.84% +- 0.03% sugar, 0.75% +-0.02% ash, and 23.3 +- 0.3 kJ g-1 whole milk (WM). At this stage, milk composition varied among individual seals in all assayed constituents except ash. The concentration of sugar in the aqueous phase of Weddell seal milk (24.9 +- 0.6 g sugar L-1 water) was ca. 4477% of levels found in terrestrial carnivores, indicating that the low sugar concentration of WM is primarily due to its high fat content, not alteration of the aqueous phase. In early lactation, fastingWeddell seals were estimated to devote 39 g d-1 glucose to milk sugar synthesis, an amount similar to the estimated demand of the maternal brain. This additional glucose demand must be covered by gluconeogenesis in fasting animals and represents a considerable additional drain on maternal resources. However, provision of sugar to offspring at rates sufficient to meet neonatal substrate requirements appears to be essential for efficient fat and protein deposition and thus may be an important component of the phocid reproductive strategy of rapid growth and early weaning. Copyright 2013 by The University of Chicago. All rights reserved.AcknowledgementsWe thank our teams who assisted in the field in 1998 (J. Banks, D. Geddes, P. Isherwood, S. Leslie, B. Stewart, H. Stoklosinski, and particularly S. Ramdohr from the Alfred-Wegener-Institute of Bremerhaven, Germany) and in 2006 (D. Boness, D. Boritt, R. Joss, B. Krafft, M. Lara, M. Riser, J. Robinson, and H. Routti). We also thank the staff at Scott Base and McMurdo Station for their support of our research. All analytical work was completed at the Nutrition Laboratory, Smithsonian National Zoological Park, and we are grateful to laboratory manager M. Jakubasz and all the interns who helped with milk analysis (1999: D. Hellinga, K. Roback, and L. Nelson; 2008/2009: J. Behler, R. Harley, M. Collins, C. Petzinger, K. Smythe, and M. Snyder). R.E. thanks M. Maslanka and M. Power for sharing their interns, J. Seidensticker for his support, and J. Noordhof for commenting on the manuscript. This work was supported by Antarctica New Zealand (field logistics in 1998), New Zealand Lotteries Science Grants Board, Science Research Grant AP52833 to G.K.B., a Smithsonian Visiting Scholar Grant to R.E., and National Science Foundation-Office of Polar Programs grant ANT-0538592 to O.T.O., R.E., and D. Boness.

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TypeArticleCitationEisert, R., Oftedal, O. and Barrell, G. (2013). Milk composition in the Weddell seal Leptonychotes weddellii: Evidence for a functional role of milk carbohydrates in pinnipeds. Physiological and Biochemical Zoology, 86(2): 159-175 IdentifierEisert2013Relevancerank5