Breeding low methane emitting sheep and elucidating the underlying biology

Summary

Genetic improvement is one method to reduce enteric methane production by grazing sheep. It is suited to extensive grazing systems where other forms of intervention are impractical. Measurements are required on large numbers of individual animals to estimate the impact of genes on methane production and establish correlations with other commercially important traits. We developed a short-term method for measuring methane in the field using portable accumulation chambers and screened over 3000 animals to estimate genetic parameters and identify high and low methane-emitting individuals to investigate their rumen physiology, rumen microbial ecology and net feed intake. Methane yield
(production/kg DMI) is related to the time feed particles spend in the rumen and sheep with high methane yield have larger rumens than sheep with lower emissions. Our preliminary work has not identified any clear differences in the microbial ecology between high and low emitting animals. Sire variation was noted in a number of traits linked to feed but there is little evidence that feed efficiency explained variation in daily methane production.  Our current estimates of heritability of methane output are low but there is enough evidence to suggest there is scope for industry to benefit through genetic selection and developing a methane index.  ​