Breeding low methane emitting sheep
This post is the first in a series of blogs written by the authors of papers which were presented at the recent Greenhouse Gases & Animal Agriculture Conference held in Dublin. All papers are published in the journal animal.
Methane is produced by rumen microbes as part of the digestive process in ruminants. These enteric emissions from farmed ruminants (e.g. cattle, sheep, goats, buffalo, and deer) contribute around 12% of global greenhouse gas emissions.
This work has now definitively shown that methane emissions produced by archaea microbes are under host genetic control. We have shown that this trait is heritable and repeatable over time and diets even after adjustment for intake. The portion of the genetic variation that was independent of intake showed no unfavourable genetic relationships with the production traits that were measured in these animals. These results indicate that it may be feasible to breed ruminants with lower methane emissions.
Divergent selection lines based on the amount of methane emitted per unit of feed eaten have now been created and detailed studies on these lines are being conducted. This includes anatomical and gene expression changes in the host, as well as changes in the microbial community and level of microbial gene expression, and changes in digestion times and passage rates and nutrient absorption. An understanding of these factors may lead to better genetic selection or alternatively identify alternative methods of reducing emissions.
However, from an industry perspective work is also progressing to identify host gene variants affecting methane emission levels and testing the robustness of these reductions to changes in diet, feeding levels, animal age and reproductive status. Simpler, cheaper and better methods of measuring this trait are also being investigated.
Heritability estimates of methane emissions from sheep, C. S. Pinares-Patiño, S. M. Hickey, E. A. Young, K. G. Dodds, S. MacLean, G. Molano, E. Sandoval, H. Kjestrup, R. Harland, C. Hunt, N. K. Pickering and J. C. McEwan