Premium
Trans ‐7, cis ‐9 CLA is synthesized endogenously by Δ 9 ‐desaturase in dairy cowsin dairy cows
Author(s) -
Corl Benjamin A.,
Baumgard Lance H.,
Griinari J. Mikko,
Delmonte Pierluigi,
Morehouse Kim M.,
Yurawecz Martin P.,
Bauman Dale E.
Publication year - 2002
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/s11745-002-0949-4
Subject(s) - butterfat , chemistry , endogeny , rumen , food science , lipidology , stearoyl coa desaturase , clinical chemistry , biochemistry , milk fat , linseed oil , gene expression , fermentation , gene
Cis ‐9, trans ‐11 and trans ‐7, cis ‐9 CLA are the most prevalent CLA isomers in milkfat. The majority of cis ‐9, trans ‐11 CLA is synthesized endogenously by Δ 9 ‐desaturase. We tested the hypothesis that trans ‐7, cis ‐9 CLA originates from endogenous synthesis by inhibiting Δ 9 ‐desaturase with a source of cyclopropene FA (sterculic oil: SO) or with a trans ‐10, cis ‐12 CLA supplement. Experiment 1 (four cows; Latin square) involved four treatments: control, SO, partially hydrogenated vegetable oil (PHVO), and PHVO+SO. Milk, plasma, and rumen fluid were collected. Experiment 2 treatments (four cows) were 0 or 14.0 g/d of 10,12 CLA supplement; milk and plasma were collected. Samples were analyzed by GC and Ag + ‐HPLC to determine FA. In Experiment 1, SO decreased milkfat content of trans ‐7, cis ‐9 CLA by 68 to 71% and cis ‐9, trans ‐11 CLA by 61 to 65%. In Experiment 2, the 10,12 CLA supplement decreased milkfat content of trans ‐7, cis ‐9 CLA and cis ‐9, trans ‐11 by 44 and 25%, respectively. Correcting for the extent of treatment‐induced inhibition of Δ 9 ‐desaturase based on changes in myristic and myristoleic acids, endogenous synthesis of trans ‐7, cis ‐9 CLA represented 85 and 102% in Experiments 1 and 2, respectively. Similar corrected values were 77 and 58% for endogenous synthesis of cis ‐9, trans ‐11 CLA. Thus, milkfat cis ‐9, trans ‐11 CLA was primarily from endogenous synthesis with a minor portion from rumen escape. In contrast, trans ‐7, cis ‐9 CLA was not present in rumen fluid in significant amounts. Results indicate this isomer in milkfat is derived almost exclusively from endogenous synthesis via Δ 9 ‐desaturase.