Ruminal methane inhibition potential of various pure compounds in comparison with garlic oil as determined with a rumen simulation technique (Rusitec)

Abstract

Ruminants represent an important source of methane (CH 4 ) emissions; therefore, CH 4 mitigation by diet supplementation is a major goal in the current ruminant research. The objective of the present study was to use a rumen simulation technique to evaluate the CH 4 -mitigating potential of pure compounds in comparison with that achieved with garlic oil, a known anti-methanogenic supplement. A basal diet (15 g DM/d) consisting of ryegrass hay, barley and soyabean meal (1:0·7:0·3) was incubated with the following additives: none (negative control); garlic oil (300 mg/l incubation liquid; positive control); allyl isothiocyanate (75 mg/l); lovastatin (150 mg/l); chenodeoxycholic acid (150 mg/l); 3-azido-propionic acid ethyl ester (APEE, 150 mg/l); levulinic acid (300 mg/l); 4-[(pyridin-2-ylmethyl)-amino]-benzoic acid (PABA, 300 mg/l). Fermentation profiles (SCFA, microbial counts and N turnover) and H 2 and CH 4 formation were determined. Garlic oil, allyl isothiocyanate, lovastatin and the synthetic compound APEE decreased the absolute daily CH 4 formation by 91, 59, 42 and 98 %, respectively. The corresponding declines in CH 4 emitted per mmol of SCFA were 87, 32, 40 and 99 %, respectively, compared with the negative control; the total SCFA concentration was unaffected. Garlic oil decreased protozoal numbers and increased bacterial counts, while chenodeoxycholic acid completely defaunated the incubation liquid. In vitro, neutral-detergent fibre disappearance was lower following chenodeoxycholic acid and PABA treatments (2 26 and 2 18 %, respectively). In conclusion, garlic oil and APEE were extremely efficient at mitigating CH 4 without noticeably impairing microbial nutrient fermentation. Other promising substances were allyl isothiocyanate and lovastatin.

An inhibitor persistently decreased enteric methane emission from dairy cows with no negative effect on milk production

“…Finally, the physico-chemical properties of the inhibitor molecule were rendered such that it will most likely not rely on an active transport mechanism to cross the archaeal cell membrane to enhance the chances of reaching its target. Several structural analogs of methyl-CoM were identified, synthesized and tested first in vitro (11) and, later on, in vivo using sheep (17) followed by beef (18,32) and dairy cattle (19,20). Thus far, all observations made in vitro and in vivo appear to be consistent with the above hypothesis, particularly the accumulation of hydrogen reported in this manuscript and the expected change in acetate and propionate proportions in ruminal fluid (33) reported elsewhere (18)(19)(20)32).…”

“…An example of the limitations of in vitro systems is a series of experiments with garlic oil. In continuous rumen culture, garlic oil was very effective in inhibiting rumen methane emission (11), but it failed to produce an effect in sheep (12). The nutrient requirements of highproducing dairy cows are much greater than those of nonlactating or low-producing cows (13) and hence any reduction in feed intake caused by a methane mitigation compound or practice would likely…”

Effects of Essential Oils on Methane Production and Fermentation by, and Abundance and Diversity of, Rumen Microbial Populations

“…The phenolic nature of ORO might explain its high potency in inhibiting both bacteria involved in feed digestion and methanogens. As the second most antimethanogenic EO, GAO did not adversely affect feed digestibility even at the highest dose tested, corroborating findings in other studies (36,45). All the other EOs appeared to reduce feed digestibility differently.…”

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

“…The addition of PTS and DDS inhibited methane emission up to 90% and 60%, respectively, which are comparable to values reported in other in vitro studies (Busquet et al, 2005;Soliva et al, 2011). Despite the methane reduction observed with the addition of PTS, DDS and BCM, only protozoal and archaeal abundances were affected by the highest dose of PTS and DDS, respectively, whereas the concentration of total bacteria remained unchanged for all treatments.…”