Widespread adoption of an effective vaccine/inhibitor package, together with the breeding of low methane-emitting animals, could deliver large emissions reductions – substantially larger than all other mitigation options combined.
If successful, such a package could release New Zealand farmers from the current situation where even best practice efforts to reduce emissions intensity are not enough to reduce total emissions from agriculture.
Apart from low-emitting sheep, however, the effectiveness and long-term sustainability of the technologies still have to be demonstrated in real farm situations.
Adoption rates will have a big effect on the net emission reductions across the livestock sector. If an inhibitor reduces methane emissions by 30% but only 10% of farmers use it, total methane emissions would be reduced by only 3% (and total greenhouse gas emissions reduction would be even smaller because this option would not reduce nitrous oxide).
So, the success of new technologies such as vaccines, inhibitors and low-emissions animals will also depend on how their adoption can be encouraged widely across New Zealand, including international market responses.
Ensuring new technologies meet all necessary regulatory requirements, such as no residues in milk or meat, will be a major test in the further development of these technologies.
Read more about methane technologies in development
Read more about current best practice options 
Read more about emissions intensity
Read more about research pipelines and the requirements for a success