ABSTRACT:The profile of trans-fatty acids and the protozoan population were evaluated in four ruminally fistulated sheep fed a diet with meadow hay: barley grain ratio (80:20%) plus sunflower oil (SO), rapeseed oil (RO) or linseed oil (LO) (5% wt/wt). The concentrate was daily mixed with individual oils and offered at 07.00 h. A 4 × 4 Latin square with 4-week periods was used. The concentration of trans-vaccenic acid (TVA) was the highest 4 h after feeding (36.1 g/100 g FA with SO; 34.5 g/100 g FA with RO) and then decreased with the time after feeding (P < 0.05). The concentration of cis9, trans11 conjugated linoleic acid (c9,t11-CLA) with RO increased from 3.23 g/100 g FA (2 h after feeding) to 4.67 g/100 g FA (4 h after feeding). The concentration of c9,t11-CLA with SO increased from 2.09 g/100 g FA (2 h after feeding) to 2.31 g/100 g FA (4 h after feeding). The concentration of c9,t11-CLA with LO was the highest 4 h after feeding (2.07 g/100 g FA). Overall effects of the oil supplements and time after feeding on short-chain fatty acids (SCFA), medium-chain fatty acids (MCFA) and long-chain fatty acids (LCFA) in the rumen fluid were evident. A strong interaction of oil supplements and time after feeding was detected in the concentration of UFA and SFA (P < 0.001). A significant effect of LO on the rumen ciliate population was observed; the total protozoan concentration and the number of Entodinium spp. were decreased as well as Dasytricha ruminantium, Isotricha spp., Polyplastron multivesiculatum, Ophryoscolex c. tricoronatus and Eremoplastron dilobum.

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The methanogenic activity in the presence of Entodinium caudatum and Epidinium ecaudatum was well preserved after long-term cultivation. Microscopic observation revealed that methane production in the presence of E. caudatum was probably caused by their intracellular methanogenic activity, while methane production in the presence of E. ecaudatum f caudatum et ecaudatum could be attributed to both the methanogenic bacterial fraction of their external surface and their intracellular activity. Methane production per protozoan cell of E. caudatum and E. ecaudatum was 2.1 nmol per cell per d and 6.0 nmol per cell per d, respectively. E. caudatum was responsible for almost the entire methane production in the culture. The activity of free methanogens constituted approximately 50% of the total methane production in the E. ecaudatum culture. Decrease of digestibility of substrates and differences in the fermentation end products accompanied the inhibition of methanogenesis in both cultures by penicillin G, streptomycin, chloramphenicol, 2-bromoethanesulfonate, and pyromellitic diimide. E. caudatum appeared to be more sensitive than E. ecaudatum to the compounds tested. Hydrogen recoveries based on both volatile fatty acids and methane production suggested that the methanogenic population appeared not to be fully able to consume hydrogen produced in the protozoan cultures. The culture conditions tested were found to be suitable for experiments on the relationship between rumen ciliates and rumen bacteria.