Efficiency values range from 15 to 40 per cent (Calsamiglia et al., 2010), showing that there is a great potential to reduce N2O emission intensity through feeding and management optimisation compared to CH4 without impairing gastrointestinal tract health and functioning. For instance, adjusting N intake to actual requirements of rumen microbes and the host animal, while taking into account rumen microbial protein synthesis and N recycling via the rumino-hepatic cycle, can considerably reduce N losses from ruminant systems (Dijkstra et al., 2013). Besides, feeding and feed management strategies, such as feed processing technologies, the use of secondary plant compounds to protect feed protein from microbial degradation or the synchronisation of N and energy supply to rumen microbes, may greatly increase duodenal protein flow and reduce ruminal ammonia absorption and, consequently, N excretion via urine. These measures will thereby enhance N use efficiency at individual animal level while modifying excreta composition and reducing N emissions from animal manures.