Partial replacement of rapeseed oil with fish oil, and dietary antioxidants supplementation affects concentrations of biohydrogenation products and conjugated fatty acids in rumen and selected lamb tissues

The purpose of this study was to assess if partial replacement of rapeseed oil (RO) with fish oil (FO) combined with dietary supplementation of various antioxidants (carnosic acid CA, selenized yeast - SeY and selenate Se(VD) influences the profile of biohydrogenation products, intermediates and conjugated fatty acids (CFA) in the rumen content and selected tissues of lambs. Thirty Corriedale male lambs were divided into 5 groups and fed for 35 days isonitrogenous and isoenergetic diets: basal diet enriched with 30 g RO/kg (Group 0 control), diet enriched with 20 g RO/kg and 10 g FO/kg (Group I) or diets with combined addition of 20 g RO/kg, 10 g FO/kg and antioxidants (Group II supplemented with 1 g CA/kg; Group III with 1 g CA/kg and 0.35 mg/kg Se as SeY; Group IV with 0.35 mg/kg Se as Se(VI)). Applied dietary modification significantly affected the lipid transformation in the rumen. Replacement of RO by FO to the greater extent affected the profile of conjugated than non-conjugated intermediates in all samples. Collateral supplementation of antioxidants acted synergistically with FO in case of CFA content in the rumen content whereas in tissues the impact of antioxidants was antagonistic to FO. Se-compounds influenced CFA amounts in the most potent way, although dependent on their chemical form. Inorganic form (Se(VI)) reduced conjugated biohydrogenation intermediates contents in lamb livers while its organic chemical form (SeY) stimulated deposition of CFA and CD in femoral muscles. Partial replacement of RO by FO resulted in preferential incorporation of CFA isomers into liver and dorsal muscle. A complex insight into PUFA metabolism in the rumen was possible due to consideration of both steps (isomerisation and biohydrogenation) as well as plethora of possible intermediates and arising products (especially conjugated). Our results indicate that isomerisation and biohydrogenation are strongly affected by the Se-compounds. The influenced depended on the chemical form of these compounds: SeY strongly influenced the isomerization of both LA and ALA, whereas inorganic Se modified the biohydrogenation of ALA. So, it can be stated that aside from phytochemicals, Se-compounds have also an ability to modify processes occurring in rumen and thus may lead to favorable modification of FA profile of edible part of ruminant carcass, which is of utmost importance from the consumer point of view.