Comparison of analytical and predictive methods for water, p

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TitleComparison of analytical and predictive methods for water, protein, fat, sugar, and gross energy in marine mammal milkAbstractMammalian milks may differ greatly in composition from cow milk, and these differences may affect the performance of analytical methods. High-fat, high-protein milks with a preponderance of oligosaccharides, such as those produced by many marine mammals, present a particular challenge. We compared the performance of several methods against reference procedures using Weddell seal (Leptonychotes weddellii) milk of highly varied composition (by reference methods: 27-63% water, 24-62% fat, 8-12% crude protein, 0.5-1.8% sugar). A microdrying step preparatory to carbon-hydrogen-nitrogen (CHN) gas analysis slightly underestimated water content and had a higher repeatability relative standard deviation (RSDr) than did reference oven drying at 100 deg C. Compared with a reference macro-Kjeldahl protein procedure, the CHN (or Dumas) combustion method had a somewhat higher RSDr (1.56 vs. 0.60 but correlation between methods was high (0.992), means were not different (CHN: 17.2 +- 0.46% dry matter basis; Kjeldahl 17.3 +- 0.49% dry matter basis), there were no significant proportional or constant errors, and predictive performance was high. A carbon stoichiometric procedure based on CHN analysis failed to adequately predict fat (reference: Rose-Gottlieb method) or total sugar (reference: phenol-sulfuric acid method). Gross energy content, calculated from energetic factors and results from reference methods for fat, protein, and total sugar, accurately predicted gross energy as measured by bomb calorimetry. We conclude that the CHN (Dumas) combustion method and calculation of gross energy are acceptable analytical approaches for marine mammal milk, but fat and sugar require separate analysis by appropriate analytic methods and cannot be adequately estimated by carbon stoichiometry. Some other alternative methods-low-temperature drying for water determination; Bradford, Lowry, and biuret methods for protein; the Folch and the Bligh and Dyer methods for fat; and enzymatic and reducing sugar methods for total sugar-appear likely to produce substantial error in marine mammal milks. It is important that alternative analytical methods be properly validated against a reference method before being used, especially for mammalian milks that differ greatly from cow milk in analyte characteristics and concentrations. Copyright 2014 American Dairy Science Association.AcknowledgementsField research on Weddell seal lactation was supported by Antarctica New Zealand (field logistics in 1998), New Zealand Lotteries Science Grants Board, a Science Research Grant no. AP52833 to G. K. Barrell, a Smithsonian Visiting Scholar grant to R. Eisert, and a National Science Foundation---Office of Polar Programs grant ANT-0538592 to O. T. Oftedal, R. Eisert, and D. Boness. We thank our teams who assisted in the field in 1998 (J. Banks, D. Geddes, P. Isherwood, S. Leslie, B. Stewart, and H. Stoklosinski from Lincoln University, Lincoln New Zealand, 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 from the Smithsonian Institution, Washington, DC). We also thank the staff at Scott Base and McMurdo Station for their support of our field efforts. We are grateful to laboratory manager M. Jakubasz for logistic and laboratory support at the Nutrition Laboratory of the Smithsonian National Zoological Park, and the interns and technicians who assisted with various aspects of milk analysis: J. Behler, D. Boen, S. Childs, M. Collins, R. Harley, D. Hellinga, K. Messerschmidt, L. Nelson, C. Petzinger, K. Roback, K. Smythe, M. Snyder, and S. Wong. We thank W. Hood, Auburn University (Auburn, AL) for her ideas about how best to estimate input factors for the stoichiometric procedure.

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1st AuthorOftedal, O.AuthorOftedal, O.Eisert, R.Barrell, G.Year2014JournalJournal of Dairy ScienceVolume97Number8Pages4713-4732DOI10.3168/jds.2014-7895URLhttps://www.scopus.com/inward/recor.....286c5a9b1ff59527ed9b44294Keywordscarbohydratecarbonfat intakehydrogennitrogenprotein intakewater, analysisanimalcalorimetrychemistrycomparative studydolphinfat intakefemalemammalmilkPinnipediaprotein intakereproducibilitywhale, AnimalsCalorimetryCarbohydratesCarbonDietary FatsDietary ProteinsDolphinsFemaleHydrogenMammalsMilkNitrogenPinnipediaReproducibility of ResultsWaterWhales, rank5Author KeywordsCarbon stoichiometryDumas methodMarine mammal milkMethod validation

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TypeArticleCitationOftedal, O., Eisert, R. and Barrell, G. (2014) Comparison of analytical and predictive methods for water, protein, fat, sugar, and gross energy in marine mammal milk. Journal of Dairy Science, 97(8): 4713-4732 doi:10.3168/jds.2014-7895