Comparative evaluation of the effects of whole essential oils and their active constituent compounds on the biohydrogenation of polyunsaturated fatty acids and fermentation characteristics of rumen microbes in vitro

Effects of whole essential oils (EOs) and their constituent compounds (EOCs) on the fermentation activities of rumen microbes and the biohydrogenation (BH) of n-3 polyunsaturated fatty acids (PUFA) were evaluated in four in vitro experiments and one feeding trial . In all the in vitro experiments, rumen fluid was collected from Hartline x Texel cross cull ewes. A basal feedstock comprising of 70:30 grass hay and concentrate was formulated, milled (1mm screen) and then supplemented with 32.5 g oil/kg (40% oil from ground whole linseed and 60% from fish oil). In the first experiment using 15 EOCs, anethole and 4 - allyanisole which were the most effective EOCs reduced the BH of 18:3 n-3 by 22.2% and 26.4%, respectively. But, at 300 mg/L there was a concomitant substantial inhibition of tot al volatile fatty acids (VFA). In the second experiment, out of 10 whole EOs, anise and cassia oils which were the most effective EOs reduced the BH of 18:3 n-3 by 58.2% and 54.3%, respectively. However, protection was accompanied with significant suppress ion of VFA at 300 mg/L. In the third experiment using varying doses (0, 100, 200 and 300 mg/L) of 4 - allylanisole, anethole, anise oil and cassia oil, it was observed that at 200, 4 - allylanisole, anethole and anise oil maintained best balance between satisfactory protection of n-3 PUFA and minimal disruption to VFA concentration. In the fourth experiment , six Hartline x Texel cross lambs were used. Three of the lambs were randomly assigned to the untreated basal diet (BDG) and the remaining three lambs were offered diet with anise oil (AOG ). Rumen fluid collected from each of the BDG and AOG was used in in vitro batch culture system. The AOG maintained higher concentrations of PUFA and lower concentration of stearic acid. Results of these studies indicate that dietary addition of selected EOs and EOCs represent a potential effective strategy to optimize the fatty acid composition of ruminant food products (to be confirmed) . However, whole EOs are more effective than EOCs.