Reducing methane emissions in sheep by immunization against rumen methanogens

This work was conducted to determine if methane emissions from sheep immunized with an anti-methanogen vaccine were significantly lower than methane emissions from non-immunized sheep, to test the effectiveness of two different vaccine formulations (VF) on methane abatement, and to compare methane emissions measured using a closed-circuit respiration chamber and the sulphur-hexafluoride (SF 6) tracer technique. Thirty mature wether sheep were randomly allocated to three treatment groups ( n=10). One group received an immunization of adjuvant only on days 0 and 153 (control), a second group received an immunization with a 3-methanogen mix on days 0 and 153 (VF3+3), and a third group received an immunization of a 7-methanogen mix on day 0 followed by a 3-methanogen mix on day 153 (VF7+3). Four weeks post-secondary immunization, there was a significant 7.7% reduction in methane production per kg dry matter intake in the VF3+3 group compared to the controls ( P=0.051). However, methane emissions from sheep immunized with VF7+3 were not significantly different when compared to the sheep in the control group ( P=0.883). The average IgG and IgA antibody titres in both plasma and saliva of the VF3+3 immunized sheep were four to nine times higher than those immunized with VF7+3 ( P