More than 30% of the Earth's total land mass is used for grazing livestock production, mainly by ruminant animals, largely due to geographical constraints on arable production. The evolutionary adaptation of the ruminant's ability to convert pasture to animal products such as meat, milk, and fibre may have been successfully harnessed, but ruminant production has an unwanted by-product. During the breakdown of plant material in the rumen, excess hydrogen is produced, and this hydrogen is metabolized by rumen microbes and eructed by the animal as methane, a potent greenhouse gas. Methane is not only an environmentally detrimental waste product but also represents ~8% digestible energy loss to the animal. The scale of this problem means that the sustainability of profitable livestock farming throughout the world is increasingly threatened by methane emissions. Proposed global agreements to lower these emissions, such as those outlined in the Kyoto Protocol and the Paris Agreement, pose an economic challenge in countries such as the UK, New Zealand, Uruguay, Ireland and others where agricultural exports from pastoral production are a major economic driver. Given that global demand for meat and milk is estimated to increase by at least 1% per annum between now and 2050, strategies for mitigation that are applicable across geographically-distinct farming systems are needed. Such a strategy would be a major scientific, economic and environmental breakthrough. There are 1.1bn sheep in the world producing around 137.8M tonnes of CO2eq (or 6.56M tonnes of CH4) per annum. Therefore, global emissions of GHG (CO2eq) due to enteric fermentation of sheep accounts for 2.6% of total agricultural emissions (FAOSTAT 2016).

The overall objective of this proposal is to request funding for portable accumulation chambers (PACs) to measure methane emissions from sheep. This equipment is essential for the measurement of individual animals' methane emissions for use in GHG mitigation strategies such as breeding approaches. Breeding animals that emit lower levels of methane is a sustainable and cumulative way to address the issue of lowering carbon emissions from Agricultural production and this equipment is integral for this to be enabled for the sheep (and potentially also goat) sectors. The UK lags behind other major sheep-producing nations such as New Zealand, Australia, France and Ireland, in that is does not yet have the equipment required to enable the integration of GHG emission reduction into sheep breeding programmes. New opportunities will be unlocked to collaborate with industry partners in projects that will use the equipment for genetic, genomic and nutritional approaches, amongst others. In particular, PAC equipment can be used to investigate links between methane emissions and information generated from the rumen microbiome, which is currently actively being addressed as part of an international EU-funded research project (GrassToGas) in which SRUC is a partner.

Technical Abstract:
The overall objective of this proposal is to request funding for portable accumulation chambers (PACs) to measure methane emissions from sheep. This equipment is essential for the measurement of individual animals' methane emissions for use in GHG mitigation strategies such as breeding approaches. PACs can be used to rapidly measure methane and other gas emissions from individual sheep at pasture which ultimately can be extended to predict feed intake in individual sheep from a variety of systems and locations, since it is portable. PACs are aluminium boxes, approximately 1m long, that house individual sheep for short periods of time (~ 50 minutes). Air samples are collected during this time and methane concentration can be analysed. Specific objectives of new research that will be undertaken using the equipment (following calibration and protocol development trials) are to quantify the amount of methane (CH4) carbon dioxide (CO2) and oxygen (O2) generated in the PACs by individual animals in order to develop new phenotypes suitable for inclusion into breeding programmes in collaboration with industry. The genetic basis of the new phenotypes will be estimated initially using standard animal breeding mixed model theory (as described in Falconer and Mackay 1996, Prentice Hall Pearson) and (depending on the availability of genotypes) will be exploited in practice to industry via genomically-enhanced breeding values (as described by Mucha et al., 2015 J. Dairy Sci. 98:8201-8208). The exploitation of this activity will be delivered via SRUC's CIEL-funded genomics pipeline in collaboration with AHDB and we anticipate that this approach will lead to cumulative reductions in methane emissions of between 1 and 3% p.a. Additional research to be proposed will align the information from the PACs with that from the CIEL-funded individual animal feed intake equipment and CT-derived data on rumen and body composition (initially via the existing ERANET GrassToGas project).