title: Transfer of absorbed cis-9, trans-11 conjugated linoleic acid into milk is biologically more efficient than endogenous synthesis from absorbed vaccenic acid in lactating cows.
abstract: Cis-9, trans-11, the major isomer of conjugated linoleic acid (CLA) in bovine milk fat, is derived from ruminal biohydrogenation of 18:2 (n-6) and endogenous conversion of trans-11 18:1 (vaccenic acid; VA) in the mammary gland. Most evidence to date suggests that endogenous synthesis is the major source of cis-9, trans-11 CLA, but the extent of VA desaturation is less well defined. Four lactating cows were used in consecutive 4 x 4 Latin squares to examine changes in milk fatty acid composition and secretion in response to abomasal infusions of lipid supplements enriched with cis-9, trans-11 CLA (88.8%) or VA (29.4%). Treatments were infused over 4-d, followed by a 3-d washout, during 7 d experimental periods and administered to deliver 0, 3, 6, and 12 g cis-9, trans-11 CLA/d (Expt. 1) or 0, 7.5, 15 and 30 g VA/d (Expt. 2). Infusions of cis-9, trans-11 CLA increased linearly milk cis-9, trans-11 CLA concentrations from 0.68 to 1.46 g/100 g fatty acids. Abomasal infusions of VA increased linearly milk VA and cis-9, trans-11 CLA content from 1.22 to 2.72 and 0.61 to 1.24 g/100 g fatty acids, respectively. Changes in milk fatty acid secretion indicated that 28.9% of VA was converted to cis-9, trans-11 CLA. Results provide evidence that conversion by Delta9-desaturase to cis-9, trans-11 CLA in the lactating cow is independent of postruminal VA supply. In conclusion, endogenous synthesis via VA was equivalent to approximately 21% of the response to increases in cis-9, trans-11 CLA available for absorption.
authors: Animal Production Research, MTT Agrifood Research Finland, Jokioinen, FIN 31600, Finland. kevin.shingfield@mtt.fi
authors: Kevin J
authors: KJ
authors: Shingfield
authors: Seppo
authors: S
authors: Ahvenjärvi
authors: Vesa
authors: V
authors: Toivonen
authors: Aila
authors: A
authors: Vanhatalo
authors: Pekka
authors: P
authors: Huhtanen
mesh_terms: D000018:Abomasum; D000042:Absorption; D000818:Animals; D002417:Cattle / Q000378:metabolism / Q000502:physiology*; D005227:Fatty Acids / Q000378:metabolism; D005260:Female; D007774:Lactation / Q000378:metabolism*; D044243:Linoleic Acids, Conjugated / Q000008:administration & dosage / Q000096:biosynthesis* / Q000493:pharmacokinetics*; D008892:Milk / Q000378:metabolism*; D009829:Oleic Acids / Q000008:administration & dosage / Q000378:metabolism* / Q000493:pharmacokinetics; D013230:Stearoyl-CoA Desaturase / Q000378:metabolism; D013237:Stereoisomerism
chemical_list: D005227:Fatty Acids; D044243:Linoleic Acids, Conjugated; D009829:Oleic Acids; C503589:cis-9, trans-11-conjugated linoleic acid; D013230:Stearoyl-CoA Desaturase; C050413:11-octadecenoic acid