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

Soliva, Carla R. ; Amelchanka, Sergej L. ; Duval, Stéphane M. ; Kreuzer, Michael

In: British Journal of Nutrition, 2011, vol. 106, no. 1, p. 114-122

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    Summary
    Ruminants represent an important source of methane (CH4) emissions; therefore, CH4 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 CH4-mitigating potential of pure compounds in comparison with that achieved with garlic oil, a known anti-methanogenic supplement. A basal diet (15g 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 (300mg/l incubation liquid; positive control); allyl isothiocyanate (75mg/l); lovastatin (150mg/l); chenodeoxycholic acid (150mg/l); 3-azido-propionic acid ethyl ester (APEE, 150mg/l); levulinic acid (300mg/l); 4-[(pyridin-2-ylmethyl)-amino]-benzoic acid (PABA, 300mg/l). Fermentation profiles (SCFA, microbial counts and N turnover) and H2 and CH4 formation were determined. Garlic oil, allyl isothiocyanate, lovastatin and the synthetic compound APEE decreased the absolute daily CH4 formation by 91, 59, 42 and 98%, respectively. The corresponding declines in CH4 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 (−26 and −18%, respectively). In conclusion, garlic oil and APEE were extremely efficient at mitigating CH4 without noticeably impairing microbial nutrient fermentation. Other promising substances were allyl isothiocyanate and lovastatin