Selenate and selenite affect ruminal metabolism of C18 unsaturated fatty acids and fatty acid composition of lamb tissues

Abstract

The main aim of our study was to investigate the influence of selenite (SeIV) or selenate (SeVI) added to ovine ruminal fluid with cis9cis12cis15C18:3 (LNA) on contents of fatty acids (FA), especially products of microbial isomerisation of LNA and biohydrogenation (BH) of unsaturated FA in vitro incubated fluids. The second goal of our study was to investigate the effects of SeVI added to a diet containing linseed oil (LO, rich in LNA) on the accumulation of BH products in selected tissues of lambs. Ruminal fluids were incubated in vitro at 39°C under CO2 either alone (the control fluid; RF) or with LNA (1.67 mg/ml), a low (1.33 μg/ml), a high (3.33 μg/ml) dose of Se (as SeIV or SeVI), with a combination of LNA with either a low (1.33 μg/ml) or a high (3.33 μg/ml) dose of Se as SeIV or SeVI. The tubes with incubated fluids were removed after 0, 6, 12, 18 or 24 h of in vitro incubation and then analysed to determine contents of FA. Both the doses of SeIV or SeVI in fluids with LNA revealed no significant effect on the contents of products of LNA isomerisation compared to incubated fluids with LNA. The contents of isomerisation products of LNA in incubated fluids with LNA, irrespective of the presence of SeIV and SeVI, rapidly increased in the fluids incubated for 6 h, followed by a slower rate of disappearance until 24 h. Contents of trans11C18:1 and trans11cis15C18:2 in fluids with LNA, regardless of the presence of both the doses of SeIV or SeVI, increased throughout incubations. The lower dose of SeVI in fluids with LNA increased the capacity of BH to trans11C18:1 in incubated fluids. SeVI added to the lambs’ diet with LO decreased contents of saturated FA (like C18:0) in the liver and musculus longissimus dorsi. LO added to the diets with or without SeVI most effectively increased the level of polyunsaturated FA (PUFA) in the liver, while the higher content of monounsaturated FA was observed in musculus biceps fermoris (MBF) when compared to the control group. The diets with LO, irrespective of the presence of SeVI, reduced the capacity of linoleic acid elongation to cis11cis14C20:2 in the liver and MBF compared to the control lambs. Further studies are required to clarify the effects of SeVI and long-chain PUFA on contents of FA, especially conjugated PUFA, in the ruminal microbiota and tissues of lambs.