Approved upon the following comment/s being actioned.

A slightly updated version of the abstract has been received. See below for text.

 Improving the understanding of dietary and manure management options for minimising greenhouse gas emissions from livestock systems: an update on two international projects.

 Arjan Jonker, Tony van der Weerden and Cecile de Klein 

 Enteric fermentation and livestock manure are major sources of greenhouse gas (GHG) emissions from agriculture. These GHGs include, enteric methane (CH4) from ruminants, and nitrous oxide (N2O), ammonia (NH3) and CH4 emissions from animal excreta deposited onto grazed land or in livestock housing systems (e.g. manure collection, storage, and land application). Feeding management has a large effect on enteric CH4 emissions and excreta composition and output, while manure composition, climate and soils affect N2O, NH3 and CH4 emissions from the different steps of the manure management system. However, there is currently limited understanding of these influential factors on on-farm GHG emissions, which hampers the development of mitigation strategies. In addition, on-farm GHG accounting tools and national agricultural GHG inventory models are limited in their ability to capture these drivers of GHG emissions. Two international projects are currently in progress to address these limitations: 
• CEDERS (Capturing Effects of Diet on Emissions from Ruminant Systems), an international consortium of ten countries (eight European countries, New Zealand and Chile) funded by FACCE ERA-GAS and national governments. The project aims to combine and interpret existing data to capture the effect of ruminant diet management on enteric CH4 and manure composition on-farm and at a national scale; and assess the impact of dietary management on system-level GHG emissions and provide insight of trade-offs/synergies between GHGs.
• DataMan, an international project (six European countries, Chile, Australia and New Zealand), funded by the Global Research Alliance (GRA) through the NZ and UK governments. The project aims to collate and analyse data on N2O, NH3 and CH4 emission factors (and all relevant activity and ancillary data) from different steps in manure management from international project participants. 

 The analysis of databases created in both projects will help to identify opportunities for GHG emissions mitigation and provide new knowledge for improving on-farm GHG accounting tools and national GHG inventories across the international consortium of countries.