Selenite and selenate affect the fatty acid profile in in vitro incubated ovine ruminal fluid containing linseed oil

Abstract

The influence of selenite (Se<sup>IV</sup>) or selenate (Se<sup>VI</sup>) added to ovine ruminal fluid containing linseed oil (LO) on the profile of fatty acids (FA), particularly conjugated linoleic acid (CLA) isomers, was investigated. The ruminal fluid was incubated in vitro at 39°C under CO<sub>2</sub> either alone (the control fluid) or with LO (3.3 mg/ml) or with a combination of LO with either a low (0.167 μg/ml) or high (1.67 μg/ml) level of Se as Se<sup>IV</sup> or Se<sup>VI</sup>. LO added to ruminal fluids also provides an extra source of energy. The tubes with the examined fluids were removed after 0, 6, 12, 18, or 24 h of in vitro incubation and then analyzed to determine the FA levels. The lower and higher concentration of Se<sup>IV </sup>in the fluids with the LO revealed negligible effect on the concentration of the sum of the CLA isomers (∑CLA) in the fluid compared with the fluid with LO alone. The addition of a higher amount of Se<sup>IV</sup> to the fluid containing LO usually decreased the concentration of ∑CLA compared with the fluid containing the lower concentration of Se<sup>IV</sup> and LO. The concentration of c9t11c15C18:3 (cLNA) in the fluids with LO, irrespective of the presence of extra Se, increased throughout the incubations, although the addition of Se<sup>IV </sup>or Se<sup>VI</sup> to the fluids containing LO numerically reduced the increase of the concentration of cLNA compared with the fluid with LO alone. The concentration sum of the C18:1 isomers (ΣC18:1) in the control fluid numerically decreased throughout the incubations, while LO added to the fluid increased the concentration of ΣC18:1 throughout the incubations. LO added to the fluid, irrespective of the presence of Se<sup>IV</sup> or Se<sup>VI</sup>, significantly increased the concentration of ΣC18:1 compared with the control fluid and the fluids with Se<sup>IV </sup>or Se<sup>VI</sup>. The concentrations of C16:0 and C18:0 in the control fluid and the fluids containing Se<sup>IV</sup> or Se<sup>VI </sup>numerically increased throughout the incubations and were usually lower than in the fluids containing LO without or with Se<sup>IV </sup>or Se<sup>VI</sup>. The concentration of C18:3n-3 decreased throughout the incubation of the fluids containing LO, irrespective of the presence of Se<sup>IV </sup>or Se<sup>VI</sup>. LO added to the fluids, irrespective of the presence of Se<sup>IV</sup> or Se<sup>VI</sup>, increased the concentration of C18:2n-6 compared with the control fluid and the fluids with Se<sup>IV </sup>or Se<sup>VI</sup>. The higher concentration of Se<sup>IV</sup> or Se<sup>VI</sup> in the fluid with LO most efficiently increased the concentration of c5c8c11c14c17C20:5 compared with the control fluid or the fluids containing LO, irrespective of the presence of the lower concentration of Se<sup>IV</sup> or Se<sup>VI</sup>. LO added to the fluid, irrespective of the presence of Se<sup>IV </sup>or Se<sup>VI</sup>, increased the concentration of polyunsaturated FA compared with the control fluid or the fluids containing Se<sup>IV </sup>or Se<sup>VI</sup>.