Feeding Strategies to Reduce Methane Emissions

The 32^nd annual Tri-State Dairy Nutrition Conference was held in Fort Wayne, IN, in April, 2024. One of the main areas of focus was dairy sustainability and Dr. Alex Hristov from Penn State University was a key speaker discussing practical nutritional approaches to reducing methane emissions. Dr. Hristov has over a decade of experience investigating dietary treatments to reduce methane production.

Three strategies were discussed in detail:

·      3-NOP is sold under the trade name of Bovaer, and is approved in Europe, Latin America, and South America to block methanogenesis in the rumen. Bovaer is not yet approved for use in the United States but is expected to gain approval in 2024. Research studies have consistently shown a 28 – 32% reduction in daily methane emission when 3-NOP if supplemented to dairy cattle.

In research studies, 3-NOP has minimal effects on intake, milk, or component yields. So even through there are changes in the rumen, there are no observable reductions in production. Some questions still exist regarding rumen adaptation to 3-NOP, as cows that are on the product longer may have reduced benefit when it comes to methane mitigation; however, few long-term studies have been performed. Additionally, early lactation animals may have a larger reduction in methane than later lactation cattle, meaning there are likely interactions between stage of lactation and methane response.

·      Macroalgae can come in many forms and the most commonly researched for methane reduction is Asparagopsis taxiformis. Headlines from research using this seaweed have reported dramatic reductions in methane emissions when supplemented at less than 0.5% of diet dry matter.

However, Hristov indicated that the large reduction in methane emissions observed when feeding macroalgae diminish over time, perhaps as the rumen adapts. Some of the reduction in methane emissions when feeding macroalgae is also from reduced intake in several studies, which results in reduced milk production and is counter to improved efficiency. There are also concerns with the ability to harvest sufficient quantity of macroalgae types to have consistent methane reduction.

·      Increasing dietary concentrates and reducing forages also reduces methane production due to changes in the rumen environment favoring propionate rather than acetate. Similarly, improving forage digestibility through earlier harvesting or hybrid selection (i.e. BMR vs. conventional hybrids) may have modest effects on reducing methane emissions. Hristov indicated that dietary manipulations without the use of feed additives would only have a modest, and sometimes inconsistent, effect on methane production.

We are likely able to make reductions in methane emissions from dairy cattle through different feeding strategies but these effects may not be additive and there may also be rumen adaptation over time. Estimates for the methane mitigation effects from these strategies will likely change over time as models are improved with the incorporation of more data. Feeding strategies are just one factor that needs to be considered as the dairy industry aims to reach carbon neutrality by 2050.