title: Rumen Microorganisms Decrease Bioavailability of Inorganic Selenium Supplements.
abstract: Despite the availability of selenium (Se)-enriched trace mineral supplements, we have observed low Se status in cattle and sheep offered traditional inorganic Se supplements. Reasons for this may include inadequate intake or low bioavailability of inorganic Se sources. The objective of this study was to determine whether rumen microorganisms (RMO) alter the bioavailability of Se sources commonly used in Se supplements. Rumen microorganisms were isolated from ewes (n = 4) and incubated ex vivo with no Se (control), with inorganic Na selenite or Na selenate, or with organic selenomethionine (SeMet). Total Se incorporated into RMO and the amount of elemental Se formed were determined under equivalent conditions. Incorporation of Se from Na selenite, Na selenate, or SeMet into RMO was measured as fold change compared with control (no added Se). Incorporation of Se into microbial mass was greater for SeMet (13.2-fold greater than no-Se control) compared with inorganic Se supplements (P = 0.02); no differences were observed between inorganic Na selenate (3.3-fold greater than no-Se control) and Na selenite (3.5-fold greater than no-Se control; P = 0.97). Formation of non-bioavailable, elemental Se was less for RMO incubated with SeMet compared with inorganic Se sources (P = 0.01); no differences were observed between Na selenate and Na selenite (P = 0.09). The clinical importance of these results is that the oral bioavailability of organic SeMet should be greater compared with inorganic Se sources because of greater RMO incorporation of Se and decreased formation of elemental Se by RMO.
authors.affiliation: Department of Biomedical Sciences, College of Veterinary Medicine, Oregon State University, Dryden Hall 206, Corvallis, OR, 97331-4802, USA.
authors.forename: M L
authors.initials: ML
authors.lastname: Galbraith
authors.affiliation: Department of Biomedical Sciences, College of Veterinary Medicine, Oregon State University, Dryden Hall 206, Corvallis, OR, 97331-4802, USA.
authors.forename: W R
authors.initials: WR
authors.lastname: Vorachek
authors.affiliation: Department of Clinical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR, 97331, USA.|Department of Animal and Rangeland Sciences, College of Agricultural Sciences, Oregon State University, Corvallis, OR, 97331, USA.
authors.forename: C T
authors.initials: CT
authors.lastname: Estill
authors.affiliation: Department of Environmental and Molecular Toxicology, College of Agricultural Sciences, Oregon State University, Corvallis, OR, 97331, USA.
authors.forename: P D
authors.initials: PD
authors.lastname: Whanger
authors.affiliation: Department of Animal and Rangeland Sciences, College of Agricultural Sciences, Oregon State University, Corvallis, OR, 97331, USA.|Linus Pauling Institute, Oregon State University, Corvallis, OR, 97331, USA.
authors.forename: G
authors.initials: G
authors.lastname: Bobe
authors.affiliation: Poisonous Plant Research Laboratory, USDA Agricultural Research Service, 1150 E 1400 N, Logan, UT, 84341, USA.
authors.forename: T Z
authors.initials: TZ
authors.lastname: Davis
authors.affiliation: Department of Biomedical Sciences, College of Veterinary Medicine, Oregon State University, Dryden Hall 206, Corvallis, OR, 97331-4802, USA. Jean.Hall@oregonstate.edu.|Funded by Agricultural Research Foundation, Oregon State University, Corvallis, OR, 97331-2219, USA. Jean.Hall@oregonstate.edu.
authors.forename: J A
authors.initials: JA
authors.lastname: Hall
mesh_terms: D000284:Administration, Oral; D000818:Animals; D001682:Biological Availability; D019587:Dietary Supplements; D005260:Female; D012417:Rumen / Q000378:metabolism* / Q000382:microbiology*; D012643:Selenium / Q000008:administration & dosage / Q000378:metabolism / Q000493:pharmacokinetics*; D012756:Sheep / Q000378:metabolism* / Q000382:microbiology*
chemical_list: D012643:Selenium
keywords: Rumen microorganisms; Ruminant; Selenium bioavailability; Selenium supplements; Sheep