Endogenous synthesis of cis-9, trans-11 conjugated linoleic acid in dairy cows fed fresh pasture.
New Zealand Holstein-Friesian cows (n = 4) were used to quantify the importance of endogenous synthesis of cis-9, trans-11 conjugated linoleic acid (CLA) via Delta(9)-desaturase in cows fed a fresh pasture diet. The experiment was a 4 x 4 Latin square design with treatments arranged in a 2 x 2 factorial. Treatments lasted 4 d and were pasture only, pasture plus sterculic oil, pasture plus sunflower oil, and pasture plus sunflower oil plus sterculic oil. Abomasal infusion of sterculic oil inhibited Delta(9)-desaturase and decreased the concentration of cis-9, trans-11 CLA in milk fat by 70%. Using the changes in cis-9 10:1, cis-9 12:1 and cis-9 14:1 to correct for incomplete inhibition of Delta(9)-desaturase, a minimum estimate of 91% of cis-9, trans-11 CLA in milk fat was produced endogenously in cows fed fresh pasture. Dietary supplementation of a pasture diet with sunflower oil increased the proportion of long chain fatty acids in milk fat; however, the increase in vaccenic acid concentration was small (18%) and there was no increase in cis-9, trans-11 CLA concentration. Overall, results show that endogenous synthesis is responsible for more than 91% of the cis-9, trans-11 CLA secreted in milk fat of cows fed fresh pasture. However, the failure of plant oil supplements to increase the concentration of cis-9, trans-11 CLA in milk fat from pasture-fed cows requires further investigation.
Kay
J K
JK
Dexcel Ltd., Private Bag 3221, Hamilton, New Zealand.
Mackle
T R
TR
Auldist
M J
MJ
Thomson
N A
NA
Bauman
D E
DE
D000818:Animals; D002417:Cattle / Q000378:metabolism*; D004032:Diet; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D044243:Linoleic Acids, Conjugated / Q000032:analysis / Q000096:biosynthesis*; D008892:Milk / Q000737:chemistry; D009829:Oleic Acids / Q000032:analysis; D010938:Plant Oils / Q000008:administration & dosage; D013230:Stearoyl-CoA Desaturase / Q000037:antagonists & inhibitors / Q000378:metabolism; D032361:Sterculia / Q000737:chemistry; D000074242:Sunflower Oil
D004791:Enzyme Inhibitors; D044243:Linoleic Acids, Conjugated; D009829:Oleic Acids; D010938:Plant Oils; D000074242:Sunflower Oil; D013230:Stearoyl-CoA Desaturase; C050413:11-octadecenoic acid