Impact of modern cattle feeding practices on milk fatty acid stable carbon isotope compositions emphasise the need for caution in selecting reference animal tissues and products for archaeological investigations

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Publisher: Springer
Document Type: Report
Length: 333 words

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To access, purchase, authenticate, or subscribe to the full-text of this article, please visit this link: Byline: Melanie Roffet-Salque (1), Michael R. F. Lee (2,3), Adrian Timpson (4), Richard P. Evershed (1) Keywords: Modern reference materials; Animal fats; Lipid residue analyses; Dairy fats; Silage Abstract: Degraded animal fats, characterised by the presence of palmitic (C.sub.16:0) and stearic (C.sub.18:0) fatty acids and related glycerolipids are the most common class of preserved lipids in organic residues trapped in the porous clay matrix of archaeological ceramic vessels. The ubiquitous presence of fatty acids in animal fats and plant oils precludes identification of fat types by the solely molecular composition of residues. Hence, animal fats are identified by determining their fatty acyl lipid distributions and stable carbon ([delt[a].sup.13]C) values allowing distinctions to be drawn between non-ruminant and ruminant, and dairy and adipose fats. The [I.sup.13]C proxy (= [delt[a].sup.13]C.sub.18:0 - [delt[a].sup.13]C.sub.16:0) originally proposed in the 1990s by Evershed and co-workers was based on modern reference fats sampled from animals raised in Britain on C.sub.3 plant diets. Further analyses on adipose and dairy fats from ruminants grazing in a wide range of isoscapes have shown that the [I.sup.13]C proxy can be applied in mixed C.sub.3/C.sub.4 environments, such as in Africa. Here we show, however, through the investigation of milk fats, how the [I.sup.13]C proxy can be perturbed when animals are reared on modern diets, specifically maize silage. It is thus shown that extreme care has to be taken when choosing modern reference fats for archaeological studies, and especially that insecurely sourced animal fats should be excluded from such databases. Author Affiliation: (1) Organic Geochemistry Unit, School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK (2) School of Veterinary Science, University of Bristol, Langford, BS40 5DU, UK (3) Rothamsted Research, North Wyke, Okehampton, EX20 2SB, UK (4) Department of Genetics, Evolution and Environment, University College London, Gower Street, London, WC1E 6BT, UK Article History: Registration Date: 13/07/2016 Received Date: 31/03/2016 Accepted Date: 13/07/2016 Online Date: 27/08/2016

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Gale Document Number: GALE|A504470976