In vitro–in vivo study on the effects of plant compounds on rumen fermentation, microbial abundances and methane emissions in goats

10 páginas, 5 tablas, 2 figuras.

Two in vitro and an in vivo experiments were conducted to investigate the effects of a selection of plant active compounds on rumen fermentation, microbial concentration and methane emissions in goats. Treatments were: control (no additive), carvacrol (CAR), cinnamaldehyde (CIN), eugenol (EUG), propyl-propane-thiosulfinate (PTS), propyl-propane-thiosulfonate (PTSO), diallyl disulfide (DDS), a mixture (40:60) of PTS and PTSO (PTS+PTSO) and bromochloromethane (BCM) as positive control with proven antimethanogenic effectiveness. Four doses (40, 80, 160 and 320 µl/l) of the different compounds were incubated in vitro for 24 h in diluted rumen fluid from goats using two diets differing in starch and protein source within the concentrate (Experiment 1).The total gas production was linearly decreased (P<0.012) by all compounds, with the exception of EUG and PTS+PTSO (P≥0.366). Total volatile fatty acids (VFA) concentration decreased (P≤0.018) only with PTS, PTSO and CAR while the acetate:propionate ratio decreased (P≤0.002) with PTS, PTSO and BCM, and a tendency (P=0.064) was observed for DDS. Based on results from Experiment 1, two doses of PTS, CAR, CIN, and BCM (160 and 320 µl/l), PTSO (40 and 160 µl/l) and DDS (80 and 320 µl/l) were further tested in vitro for 72 h (Experiment 2). The gas production kinetics were affected (P≤0.045) by all compounds, and truly digested DM (tDMD) after 72 h of incubation was only linearly decreased (P≤0.002) by CAR and PTS. The addition of all compounds linearly decreased (P≤0.009) methane production, although the greatest reductions were observed for PTS (up to 96%), DDS (62%) and BCM (95%). No diet x dose interaction was observed. To further test the results obtained in vitro, two groups of sixteen adult non-pregnant goats were used to study in vivo the effect of adding PTS (50, 100 and 200 mg/l rumen content per day) and BCM (50, 100 and 160 mg/l rumen content per day) during 9 days on methane emissions (Experiment 3). The addition of PTS and BCM resulted in a linear reduction (33% and 64%, respectively, P≤0.002) of methane production per unit of dry matter intake, which were lower than the maximum inhibition observed in vitro (87 and 96 %, respectively). We conclude that applying the same doses in vivo as in vitro resulted in proportional lower extent of methane decrease and that PTS at 200 mg/l rumen content per day has the potential to reduce methane emissions in goats. Whether the reduction in CH4 emission observed in vivo persists over longer periods of treatments and improves feed conversion efficiency requires further research.

This research was supported by the Science and Innovation Spanish Ministry (Project AGL2008-04707-C02-01). The authors acknowledge J. Fernández, T. García, E. Jiménez, I. Jiménez and F. Ramos-Morales for their technical assistance, P. Frutos for constructive criticism of design and analysis, and DMC Research Center S.L. for providing PTS and PTSO. G. Martínez gratefully acknowledges the FPI grant from the Spanish Science Ministry.

Peer reviewed