Dr. Jan Dijkstra is an expert in dairy cattle nutrition focused mainly on challenges in dairy cattle nutrition aiming for healthy animals producing milk at low environmental costs. Dijkstra conducts a broad-based experimental research programme to understand and quantify the relationships between diet quality or dietary additives and enteric methane emissions of dairy cattle. His research has contributed to improved understanding of relationships between diet quality and enteric methane emissions, and of trade-offs between dietary changes to mitigate methane emissions and reducing nitrogen and phosphorus excretion in dairy cattle. With several colleagues, Jan Dijkstra developed advanced mechanistic models of fermentation in cattle, that are applied as official IPCC Tier 3 approaches to estimate enteric methane emissions and faecal digestibility of dairy cattle for national inventory purposes of methane and ammonia emissions of dairy cattle. His expert research on methane emission and on nitrogen excretion received wide attention globally and has been featured on national and international TV and radio as well as in numerous newspapers.