Unlocking the Potential of Phytochemicals for Improved Sustainability and Animal Health in Pastured Dairy Systems

Commodities

Practices

Reducing greenhouse gas (GHG) emissions in dairy production is a pressing concern yet a highly daunting task. Promising methane inhibitors (e.g., 3-nitrooxypropanol) and feed additives (e.g., algae) are neither practicable nor widely accessible in organic and pasture-based systems. While chemical inhibitors hold promise, the challenge lies in ensuring their ingestion with every bite for effectiveness, which is easier to achieve in feedlot systems than in pastures. Overall, the mitigation strategies for pasture-based ruminant production systems are either largely unavailable or rarely implemented in practice. Phytochemicals (e.g., tannins, sesquiterpene lactones) found in forbs are powerful tools for pasture-based dairy farming to enhance animal health and reduce GHG emissions. Bioactive plant compounds such as condensed tannins (CT) help reduce enteric methane (CH₄) emissions and decrease nitrogen loss in urine by protecting dietary protein from degradation in the rumen. Our farmers recognize the benefits of forbs but seek guidance on optimal proportions in mixtures, variety selection for higher levels of bioactive compounds, and management practices to maximize their efficacy and environmental benefits in a cost-efficient manner. However, no studies have systematically assessed these phytochemicals at the varietal level or designed phytochemically diverse pastures (chemoscapes) and documented their impacts on animal health, milk yield, feed intake, GHG emissions and production cost based on this knowledge. This is a major barrier to achieving meaningful GHG reductions through plant-based CH₄ mitigators in dairy farming. To address these knowledge gaps, we propose to quantify a broad spectrum of bioactive compounds across a range of forbs at the varietal level at different phenological growth stages. We will measure the seasonal herbage production and chemical composition of the forbs and assess the individual and combined GHG reduction potentials of phytochemicals through an in-vitro screening study (Objective 1). We will assess the potential of pasture chemoscapes by collecting measures of productivity (e.g., milk yield, feed utilization), sustainability (e.g., GHG emissions), and animal health (e.g., immune function, fecal egg counts) through a replicated grazing experiment in spring, summer and fall seasons (Objective 2). With input from the advisory team, and based on the findings of our previous experiments and the in-vitro screening trial, we will establish chemoscapes on dairy farms across Oregon and Washington. Through these on-farm trials, we will educate farmers, coordinate field days, and quantify the economic and environmental sustainability of the chemoscapes (Objective 3). We will develop an extension program to educate producers on chemoscapes and disseminate study results (Objective 4). Our long-term goal is to develop a sustainable and resilient pasture-based dairy system that maintains high levels of animal performance and health while also supporting the overall health of the pasture and production ecosystem.

Objective 1: Agronomic and in-vitro screening of forbs to assess their forage yield, nutritive value, and potential to reduce CH₄ emissions

Objective 2: Assessing the effect of pasture chemoscapes on soil GHG emissions and health, milk yield, methane emissions, and nitrogen partitioning in dairy cows

Objective 3: On-farm bioeconomic evaluation of phytochemically diverse pastures and farmer education on chemoscape design

Objective 4: Develop an education and extension program on diverse chemoscapes for dairy producers and students