Modelling impact of feed supplements on methane emissions in dairy cattle

Livestock contributes to climate change, accounting for 30% of global anthropogenic methane (CH4) emissions, primarily originating from enteric fermentation by ruminants. Ruminant production sectors are committed to significantly mitigate CH4 emissions and limit global warming. Dietary supplementation of CH4 inhibitors decreases enteric CH4 emissions with considerable variability, ranging from 10 to 80%, through two main modes of action: substrate competition and enzymatic inhibition of methanogenesis. Achieving future CH4 mitigation targets is unlikely without these additives. Hence, practical implementation tools are essential. Rumen and hindgut methanogenesis are simulated using mechanistic models, contributing to understand their biological complexity. However, the mode of action of CH4 inhibitors in the rumen has not been mechanistically represented yet, and certain aspects of their functionality still remain unclear. These mechanistic models would enhance our understanding of inhibitor action dynamics, allowing for the prediction of variable effectiveness of inhibitors under different feeding regimes, inhibitor dosages, and when various inhibitors are combined. The aim of this project is to develop mechanistic submodels to represent and gain a deeper understanding of the modes of action of anti-methanogenic feed additives (3-nitrooxypropanol, bromoform) and a selection of dietary supplements (nitrate, fats). These models will then be integrated into an extant digestive tract model currently used to calculate CH4 emissions from dairy cattle for the Dutch national inventory of GHG emissions. Therefore, the developed models in this project will enable the estimation and accounting of efforts made by the cattle sector (in particular dairy sector) to reduce enteric methane emissions. Within the present project, mechanistic models for each additive/supplement will be developed based on well-established fundamental principles and will be calibrated using experimental in-vivo data. This work will be conducted in collaboration with industrial partners representing the dairy industry and companies involved in the development of feed additives or dietary supplements.