Impact of essential oils on methane emissions, milk yield and feed efficiency and resulting influence on the carbon footprint of dairy production systems

Reducing CO2 emissions is one of the highest priorities in animal production. Regarding methane reduction, feed additives are of growing importance. As shown in a meta-analysis, the use of the essential oil (EO) blend Agolin Ruminant affects methane production per day (-8.8%), milk yield (+4.1%) and feed efficiency (+4.4%). Building on these results, the present study investigated the effect of varying individual parameters on the carbon footprint of milk. The environmental and operational management system REPRO was applied to calculate the CO2 emissions. It enables a scenario suitability on the smallest investigation level (feeding group) and an indicator-based assessment of climate-relevant environmental impacts. Within the farm, CO2 emissions include potential emissions of enteric and storage-related CH4, storage- and pasture-related N2O as well as direct and indirect energy expenditures for the housing system. Three feed rations were created, differing in their basic feed components such as grass silage, corn silage and pasture. Due to the reducing effect of EO on enteric methane production alone, a reduction potential of up to 6% could be calculated for all rations. Considering other variable parameters, such as the positive effects on ECM yield and feed efficiency, a GHG reduction potential of up to 10%. Modeling showed that indirect methane reduction strategies are important contributors to environmental impacts. To provide a context for interpretation, it can be assumed that reduction of enteric methane emissions is fundamental, as they account for the largest share of GHG emissions from dairy production.