Effects of rumen exposure to anise oil on ruminal fermentation and biohydrogenation of N–3 polyunsaturated fatty acids

P.O Eburu,S Chikunya,P.O Ozung,M.I Anya

doi:10.4314/gjpas.v23i2.3

Abstract

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 (200 g) 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 NH 3 -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 NH 3- 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), trans vacceric 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.

Highlights

Essential oils (EOs) which are known as volatile oils are aromatic oily liquids (Guenther, 1948; Burt, 2004), extracted from different parts of plants such as the stem, leaves, seeds, roots, etc
The concentrations of NH3-N, total volatile fatty acid (TVFA) and molar proportions of individual volatile fatty acid (VFA) were not affected by treatments
In this experiment the fluid exposed to anise oil (AOG) and the unexposed fluid (BDG) maintained similar levels of total gas production

Summary

Introduction

Essential oils (EOs) which are known as volatile oils are aromatic (relating to the smell and taste) oily liquids (Guenther, 1948; Burt, 2004), extracted from different parts of plants such as the stem, leaves, seeds, roots, etc The presence of these EOs in plants are thought to be responsible for the unique smell produced by plants due to the different smells and aroma produced by different EOs (Szumacher-Strabel and Cieslak, 2012). In our previous studies (Eburu and Chikunya, 2015a; b), it was established that certain EOCs (e.g. anethole and 4-allylanisole) and whole EOs (e.g. anise oil) when added at 200 mg/L can significantly suppress biohydrogenation of PUFA without detrimental effects to fermentation and VFA concentrations. About four weeks’ period of microbial adaptation was suggested as the minimum time required to modify Nitrogen metabolism in the rumen by some of these studies

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