cis-9, trans-11 conjugated linoleic acid is synthesized directly from vaccenic acid in lactating dairy cattle.
The utilization of (13)C-labeled vaccenic acid (VA) by lactating dairy cows to synthesize cis-9, trans-11 conjugated linoleic acid (CLA) was investigated. Primiparous ruminally cannulated Holstein cows (n = 3) were abomasally infused with 1.5 g of VA-1-(13)C. Blood and milk samples were taken frequently before and after VA infusion. Milk and plasma lipid were extracted using chloroform:methanol. Plasma lipid was separated into triacylglycerol (TG), cholesterol ester (CE), phospholipid (PL), nonesterified fatty acid (NEFA), and mono- and diacylglycerol (MDG) fractions. Lipid was methylated, converted to dimethyl disulfide and Diels-Alder adducts, and analyzed by GC-MS. Increased enrichment of (13)C was determined using a 2-sample t test for each sample time compared with -24 h, with significance declared at P < 0.05. Enrichment in milk fat VA was detected at 4 (3.0%), 8 (8.3%), 12 (4.1%), 16 (2.2%), and 20 h (0.8%). Enrichment in VA was also detected in plasma TG, NEFA, PL, and MDG. Enrichment in milk fat cis-9, trans-11 CLA, the Delta9-desaturase product of VA, was detected at 4 (2.6%), 8 (6.6%), 12 (3.4%), 16 (1.7%), and 24 h (0.7%). Enrichment was not detected in cis-9, trans-11 CLA for any plasma lipid fraction. Modeling of the data showed the exponential decay in (13)C enrichment over time for both VA and cis-9, trans-11 CLA in milk fat. Conversion of dietary VA to cis-9, trans-11 CLA endogenously was confirmed with the mammary gland being the primary site of Delta9-desaturase activity; approximately 80% of milk fat cis-9, trans-11 CLA originated from VA.
Department of Animal and Veterinary Science, College of Agricultural and Life Sciences, University of Idaho, Moscow, ID 83844-2330, USA.
Erin E
EE
Mosley
Bahman
B
Shafii Dagger
Peter J
PJ
Moate
Mark A
MA
McGuire
D000821:Animal Feed; D000818:Animals; D002247:Carbon Isotopes; D002417:Cattle; D004043:Dietary Fiber; D005260:Female; D007774:Lactation / Q000502:physiology*; D044243:Linoleic Acids, Conjugated / Q000096:biosynthesis*; D008055:Lipids / Q000032:analysis; D008892:Milk / Q000737:chemistry; D009829:Oleic Acids / Q000378:metabolism*; D012820:Silage
D002247:Carbon Isotopes; D004043:Dietary Fiber; D044243:Linoleic Acids, Conjugated; D008055:Lipids; D009829:Oleic Acids; C503589:cis-9, trans-11-conjugated linoleic acid; C050413:11-octadecenoic acid