title: Identification and ruminal outflow of long-chain fatty acid biohydrogenation intermediates in cows fed diets containing fish oil.
abstract: The abundance of 20- to 24-carbon fatty acids in omasal digesta of cows fed grass silage-based diets supplemented with 0 (Control) and 250 g/day of fish oil (FO) was examined to investigate the fate of long-chain unsaturated fatty acids in the rumen. Complimentary argentation thin-layer chromatography and gas-chromatography mass-spectrometry analysis of fatty acid methyl esters and corresponding 4,4-dimethyloxazoline derivatives prepared from fish oil and omasal digesta enabled the structure of novel 20- to 22-carbon fatty acids to be elucidated. Compared with the Control, the FO treatment resulted in the formation and accumulation of 27 novel 20- and 22-carbon biohydrogenation intermediates containing at least one trans double bond and the appearance of cis-14 20:1, 20:2n-3, 21:4n-3 and 22:3n-6 not contained in fish oil. No conjugated ≥ 20-carbon fatty acids were detected in Control or FO digesta. In conclusion, fish oil in the diet results in the formation of numerous long-chain biohydrogenation intermediates in the rumen of lactating cows. Comparison of the intake and flow of 20-, 21- and 22-carbon fatty acids at the omasum in cows fed the Control and FO treatments suggests that the first committed steps of 20:5n-3, 21:5n-3 and 22:6n-3 hydrogenation in the rumen involve the reduction and/or isomerisation of double bonds closest to the carboxyl group.
authors.affiliation: Animal Production Research, MTT Agrifood Research Finland, 31600, Jokioinen, Finland.
authors.forename: Piia
authors.initials: P
authors.lastname: Kairenius
authors.forename: Vesa
authors.initials: V
authors.lastname: Toivonen
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Shingfield
mesh_terms: D000821:Animal Feed / Q000032:analysis*; D000818:Animals; D002417:Cattle; D002855:Chromatography, Thin Layer / Q000379:methods; D004032:Diet / Q000662:veterinary*; D019587:Dietary Supplements; D005227:Fatty Acids / Q000032:analysis* / Q000378:metabolism; D005228:Fatty Acids, Essential / Q000032:analysis*; D015525:Fatty Acids, Omega-3 / Q000032:analysis; D043371:Fatty Acids, Omega-6 / Q000032:analysis; D005260:Female; D005395:Fish Oils / Q000008:administration & dosage* / Q000032:analysis*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods; D006865:Hydrogenation; D007774:Lactation; D012417:Rumen / Q000737:chemistry* / Q000378:metabolism
chemical_list: D005227:Fatty Acids; D005228:Fatty Acids, Essential; D015525:Fatty Acids, Omega-3; D043371:Fatty Acids, Omega-6; D005395:Fish Oils