Assimilation and deposition of dietary fatty alcohols in Leach's storm petrel,Oceanodroma leucorhoa

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Abstract
The diet of Leach's storm petrel (Oceanodroma leucorhoa) chicks has a high lipid content (up to 60% of fresh mass), and, for certain populations, much of the dietary lipids are wax esters (up to 70% of total lipid). In order to determine the metabolic fate of dietary wax esters, we fed chicks [1‐14C]cetyl oleate in either a low wax (20%, w/w) or a high wax (80%, w/w) mixture of wax ester and triacylglycerols. Wax ester in the stomach remained unhydrolyzed for extended periods, with up to 38% of the label still unassimilated after 36 hr. Hydrolysis occured principally in the duodenum, where the fatty alcohol product was rapidly oxidized to fatty acid, apparently at the intestinal epithelia. Assimilated label was primarily metabolized and respired as carbon dioxide, with most of the remainder incorporated into triacylglycerols and deposited in storage fat depots. Hydrolysis of wax ester and assimilation of the fatty alcohol moiety were extremely efficient, with less than 0.2% of ingested label excreted. Assimilation efficiencies for label in low wax and high wax meals were statistically indistinguishable. Chicks fed 20% (w/w) [1‐14C]cetyl alcohol in triacylglycerols had similar assimilation efficiencies as those fed labeled wax ester, indicating that hydrolysis of the ester linkage does not limit wax ester assimilation. This study suggests that sea birds can possess an efficient means for metabolizing wax esters, an abundant energy source in the marine environment, which have previously been thought to be difficult to assimilate.

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