title: Gastrointestinal metabolism of phytoestrogens in lactating dairy cows fed silages with different botanical composition.
abstract: Dietary phytoestrogens are metabolized or converted in the gastrointestinal tract of ruminants, only limited knowledge exists on the extent and location of this conversion in vivo. The objective of this study was to quantify the gastro-intestinal metabolism of phytoestrogens in lactating dairy cows fed silages with different botanical composition. Four lactating rumen cannulated Norwegian Red cattle were assigned to a 4 × 4 Latin square with 1 cow per treatment period of 3 wk. The 4 treatment silages were prepared from grasslands with different botanical compositions: organically managed short-term timothy (Phleum pratense L.) and red clover (Trifolium pratense L.) ley (2 yr old: ORG-SG); organically managed long-term grassland with a high proportion of unsown species (6 yr old; ORG-LG); conventionally managed perennial ryegrass (Lolium perenne L.) ley (CON-PR); and conventionally managed timothy ley (CON-TI). The herbages were cut, wilted, and preserved with additive in round bales, fed as a mix of the first and third cut at 90% of ad libitum intake, and contributed to 70% of the total dry matter intake. Milk, feed, omasal digesta, urine, and feces were collected at the end of each period and analyzed for the concentrations of phytoestrogens by using a liquid chromatography-tandem mass spectrometry technique. Concentration of total isoflavones was highest in ORG-SG and lowest in CON-TI silage, whereas the content of total lignans was highest in the grass silages. The isoflavones were extensively metabolized in the rumen on all diets, and the recovery of formononetin and daidzein in omasum, mainly as equol, averaged 0.11 mg/mg. The apparent intestinal metabolism was less severe as, on average, 0.29 mg/mg of the omasal flow was recovered in feces. The plant lignans were also strongly degraded in the rumen. However, the flow of lignans to omasum and excretion in feces were, on average, 7.2- and 5.2-fold higher, respectively, than the intake of the plant lignans matairesinol and secoisolariciresinol, known as precursors of mammalian lignans. Thus, excretion to milk could not be directly related to intake, implying that plant lignans other than matairesinol and secoisolariciresinol in forage are precursors for enterolactone production in the rumen and for its content in milk. Equol followed mainly the flow of large particles out of the rumen, whereas the mammalian lignans were distributed between phases proportional to dry matter flow. The main metabolism of phytoestrogens occurred in the rumen and the main route of excretion was through feces and urine, with only a small part being excreted in milk. The concentration of phytoestrogens in milk can be manipulated through intake but the intermediate transfer capacity to milk appears to be limited by saturation.
authors.affiliation: Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences, PO Box 5003, 1432 Ås, Norway. Electronic address: havard.steinshamn@bioforsk.no.
authors.forename: K M
authors.initials: KM
authors.lastname: Njåstad
authors.affiliation: Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences, PO Box 5003, 1432 Ås, Norway; Bioforsk-Norwegian Institute of Agricultural and Environmental Research, Organic Food and Farming Division, Gunnars veg 6, 6630 Tingvoll, Norway.
authors.forename: S A
authors.initials: SA
authors.lastname: Adler
authors.affiliation: Department of Animal Science, Aarhus University, Blichers Allé 20, Postboks 50, 8830 Tjele, Denmark.
authors.forename: J
authors.initials: J
authors.lastname: Hansen-Møller
authors.affiliation: Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences, PO Box 5003, 1432 Ås, Norway.
authors.forename: E
authors.initials: E
authors.lastname: Thuen
authors.affiliation: Department of Agricultural Research for Northern Sweden, Swedish University of Agricultural Sciences, 901 83 Umeå, Sweden.
authors.forename: A-M
authors.initials: AM
authors.lastname: Gustavsson
authors.affiliation: Bioforsk-Norwegian Institute of Agricultural and Environmental Research, Organic Food and Farming Division, Gunnars veg 6, 6630 Tingvoll, Norway.
authors.forename: H
authors.initials: H
authors.lastname: Steinshamn
mesh_terms: D000818:Animals; D002417:Cattle / Q000378:metabolism*; D002853:Chromatography, Liquid; D004032:Diet / Q000662:veterinary; D005243:Feces / Q000737:chemistry*; D005260:Female; D005663:Furans; D007529:Isoflavones / Q000032:analysis* / Q000378:metabolism* / Q000652:urine; D007774:Lactation / Q000378:metabolism; D017705:Lignans / Q000032:analysis / Q000378:metabolism; D008129:Lolium / Q000378:metabolism; D013058:Mass Spectrometry; D008892:Milk / Q000737:chemistry*; D009851:Omasum / Q000737:chemistry; D031784:Phleum / Q000378:metabolism; D048789:Phytoestrogens / Q000032:analysis* / Q000378:metabolism* / Q000652:urine*; D006109:Poaceae / Q000378:metabolism; D012417:Rumen / Q000378:metabolism; D012820:Silage / Q000032:analysis*; D029921:Trifolium / Q000378:metabolism
chemical_list: D005663:Furans; D007529:Isoflavones; D017705:Lignans; D048789:Phytoestrogens; C007768:formononetin; C068935:matairesinol; C004742:daidzein
keywords: isoflavone; lignan; recovery; silage