Animal Feed Science and Technology 144 (2008) 44–54 Available online at www.sciencedirect.com Comparison of fatty acid composition of bacterial and protozoal fractions in rumen fluid of sheep fed diet supplemented with sunflower, rapeseed and linseed oils Zora V´ aradyov´ a ∗ , Svetlana Kiˇ sidayov´ a, Peter Siroka, Duˇ san Jalˇ c Institute of Animal Physiology, Slovak Academy of Sciences, ˇ Solt´ esovej 4-6, 040 01 Koˇ sice, Slovak Republic Received 23 April 2007; received in revised form 24 September 2007; accepted 26 September 2007 Abstract The objective of this study was to investigate effects of oil supplements on the composition of fatty acids (FA), especially of trans11-C18:1 (vaccenic acid, TVA) and cis9, trans11-C18:2 conjugated linoleic acid (c9,t11-CLA), in bacterial (BF) and protozoal (PF) fractions of rumen fluid of sheep that was fractionated centrifugation. Four sheep were fed a diet consisting of meadow hay (960 g dry matter (DM)/day) and of barley grain (240 g DM/day), with sunflower oil (SO), rapeseed oil (RO) or linseed oil (LO) as supplements (60 g/day) in a Latin square design. The oils were used as they are rich in linoleic acid (SO, 533g/kg of FA), oleic acid (RO, 605g/kg of FA) and -linolenic acid (LO, 504 g/kg of FA). Compared to the control (i.e., without oils), oil supplements influenced the concentration of unsaturated (UFA) and saturated fatty acids (SFA). In both BF and PF, the main fatty acids were palmitic and stearic, but PF contained a higher proportion of TVA and c9,t11-CLA than BF. In PF, TVA concentrations, ranked by oil supplement, were SO > RO > LO > Control (174, 150, 118, 74g/kg of FA, respectively) and the c9,t11-CLA concentrations were RO > SO > LO > Control (59, 51, 27 and 15g/kg of FA, respectively). Concentrations of c9,t11-CLA in PF were two to three Abbreviations: BF, bacterial fraction; c9,t11-CLA, cis9trans 11-C18:2 conjugated linoleic acid; CLA, con- jugated linoleic acid; CO, control; DM, dry matter; F, fraction; F × O, fractions and oils interaction; FA, fatty acids; LCFA, long-chain fatty acids; LO, linseed oil; MCFA, medium chain fatty acids; O, oil; PF, protozoal fraction; RO, rapeseed oil; SCFA, short chain fatty acids; SFA, saturated fatty acids; SO, sunflower oil; TVA, trans11-C18:1-vaccenic acid; UFA, unsaturated fatty acids. ∗ Corresponding author. Tel.: +421 55 728 7841; fax: +421 55 728 7842. E-mail address: varadyz@saske.sk (Z. V´ aradyov´ a). 0377-8401/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.anifeedsci.2007.09.033