Effect of microbial oil, evening primrose oil and borage oil on rumen fermentation in vitro

Abstract

The objective of this study was to examine the effects of microbial oil, evening primrose oil and borage oil on rumen fermentation of a diet consisting of 80% of hay and 20% of barley in an artificial rumen (Rusitec). All three oils contained gamma-linolenic acid (GLA), microbial oil – 8.4%, evening primrose oil – 9.2% and borage oil – 23.7% out of the total fatty acid content. The experiment in Rusitec lasted 11 days. After a stabilization period (5 days), microbial oil (5% wt/wt) was added into fermentation vessel V<sub>2</sub>, evening primrose oil (5% wt/wt) into V<sub>3</sub> and borage oil (5%wt/wt) into V<sub>4</sub> (6 days). Fermentation vessel V<sub>1</sub> served as a control (without oils). The results showed that the oils did not affect any of the basal parameters of rumen fermentation (pH, NH<sub>3</sub>-N, degradation of dry matter, organic matter, neutral detergent fibre, acid detergent fibre). Methane production (mmol/day) was reduced numerically by the oils; microbial oil, evening primrose oil and borage oil decreased CH<sub>4</sub> production about 11.32%, 11.45% and 2.04%, respectively. The supplementation of the oils to the total mixed ration (TMR) significantly decreased percentage proportions of short-chain fatty acids (SCFA, about 0.1–0.3%), medium-chain fatty acids (MCFA, about 8%) and increased long-chain fatty acids (LCFA, about 8%) in the effluent. Stearic acid C<sub>18:0</sub> was the major FA in the effluent and was significantly reduced in oil supplemented diets. The percentage proportion of trans C<sub>18:1</sub> isomers significantly increased (1.7–2 times) in all oil supplemented diets. The main intermediates – cis 9, trans 11 C<sub>18:2</sub> (CLA) and trans 11 C<sub>18:1 </sub>(TVA) also increased after oil supplementation of the diet. TVA concentration with microbial oil, evening primrose oil and borage oil supplementation was 3.17%, 8.19% and 9.3% in comparison with the control (1.38%). CLA concentration significantly increased 2.3, 1.2, and 2.1 times after microbial oil, evening primrose oil and borage oil supplementation in Rusitec. Finally, the oil supplementation caused incomplete biohydrogenation of unsaturated FA and it was characterized by an increase in TVA concentration and TVA to C<sub>18:0</sub> ratio in oil supplemented diets.