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This study evaluated the effect of four weeks of microbial exposure to anise oil (ANO) on the fermentation activities of ruminal micro-organisms and the biohydrogenation of n-3 polyunsaturated fatty acids (PUFA). A total of six Hartline ×
Texel cross lambs were used. Three of the lambs were randomly assigned to the basal diet (basal diet group, BDG) and the remaining three lambs were offered basal diet with ANO (anise oil group, AOG) for four weeks. The rumen fluid donor lambs were offered water and hay ad libitum and supplemented with additional 400 g/sheep/day of concentrate plus 2.4 g/sheep/day of ANO (for the AOG). The ANO was thoroughly mixed with the concentrate prior to feeding. The total amount (400 g) of lamb finisher cubes offered per sheep/day was divided into two equal parts (200g) and fed at 08.00 and 16.00 hours, respectively. After the four weeks’ exposure period, lambs were slaughtered and ruminal fluid (RF) was collected from each of the lambs on BDG and on AOG and used in a 48 h in vitro batch culture system to study the fermentation of a 70: 30 grass hay (Lolium perenne) and concentrate (lamb finisher) diet. The study was a 2 (batches of rumen fluid: BDG and AOG) × 2 (doses of ANO: 0 and 200 mg/L) factorial design experiment. Results showed that total volatile fatty acid (TVFA) in RF extracted from lambs on the BDG (242.0 mM) was similar to that in the AOG (242.2 mM). Concentrations of TVFA in in vitro digests were similar between groups on the BDG (68.6 mM) and on the AOG (66.4 mM), but differed between levels of anise oil (0 versus 200 mg/L). The levels of NH3-N were not different (P>0.05) between the RF collected from AOG and BDG. However, in vitro results showed that AOG 200 mg/L induced a 20% decrease on the concentration of NH3-N in fermentation vessels, relative to BDG 0 mg/L. The in vitro digesta incubated in RF from the AOG (i.e. AOG 200 mg/L) maintained higher concentrations of PUFA (C18:2 n-6 and n-3 PUFA), transvacceric acid and lower concentration of stearic acid. This suggests that there was no rumen adaptation within the period of trial. This study concludes that anise oil is potentially a useful feed additive to optimise the fatty acid composition of ruminant feedstuffs, if these effects are repeated in meat and milk.
Keywords: Rumen filtrate, anise oil, biohydrogenation, polyunsaturated fatty acid