Characterizing and Quantifying Grape Marc in Reducing Enteric Emissions

RESEARCHER: Ermias Kebreab, UC Davis

TIMELINE: January – December 2023

BACKGROUND: Grape marc (i.e., pomace) contains high concentrations of condensed tannins and is a readily available byproduct from California’s viticulture industry. A recent study in Australia found that feeding grape marc to dairy cows could lead to a 14-20% reduction in methane production.

OBJECTIVE: To investigate the potential of grape marc to reduce methane emissions and improve modulation of the gut microbiota with potential benefits for human health.

INDUSTRY BENEFIT: Use of grape marc in dairy diets could benefit California dairy in three ways: 1) Upscaling an abundant byproduct of the California wine industry, which will reduce emission intensity; 2) Reducing methane emissions could help in meeting the 40% reduction mandated by the state; 3) Changes in milk fatty acid composition (due to the tannin’s in grape marc) in the diet may have beneficial human health impacts.