Short Communication: Diurnal Profiles of Conjugated Linoleic Acids and Trans Fatty Acids in Ruminal Fluid from Cows Fed a High Concentrate Diet Supplemented with Fish Oil, Linseed Oil, or Sunflower Oil

Abstract

Trans-18:1 and 18:2 isomer composition in ruminal fluid during the daily feeding cycle was examined in 3 cows fed a high concentrate diet (35:65) with 5% (DM basis) sunflower oil (SO), 5% linseed oil (LO), or 2.5% fish oil (FO) in a 3×3 Latin square with 3 4-wk periods. Grass hay and concentrate mixtures were fed at 0900, 1300, and 1700h daily. Ruminal fluid was collected at 0900, 1100, 1300, 1500, 1700, 2000, and 0000h. Feeding SO resulted in the greatest mean concentrations (% of total fatty acids) of trans10,cis12-18:2 and cis9,trans11-18:2. In particular, trans10,cis12-18:2 with SO was greater at 1500 (0.29%), 2000 (0.34%), and 0000h (0.25%) relative to 0900h (0.07%). Cis9,trans11-18:2 concentration increased from 0.47% at 0900h to a peak of 2.06% at 1100h; it remained greater than the percentage determined at 0900h at 1300 (1.4%) through 0000h (1.1%). Concentration of trans11,cis15-18:2 was greatest with LO, ranging from 3.3% (0900h) to a peak of 11.4% at 2000h. Mean trans10-18:1 concentration ranked by diet was SO>FO>LO. Peak trans10-18:1 with SO was observed at 1700h (14.9%) compared with 0900h (5.1%). Trans11-18:1 did not differ with diet or time. Stearic acid decreased over time with all diets reaching minimum concentrations at 1700 to 2000h relative to 0900h. Feeding FO, however, decreased mean 18:0 concentration 4-fold compared with LO or SO. The moderate effect on concentration of trans-18:1 coupled with accumulation of 18:2 intermediates and the decrease of 18:0 over time suggest that oils reduced the biohydrogenation of 18:2 isomers to trans-18:1.