There are few industries that have the power to significantly reduce their carbon footprint, but the dairy industry has the opportunity to do so. A comprehensive analysis suggests certain strategies that could lower global methane emissions from human activities by 50% and slow global warming by 30%. To help achieve this, Penn State University professor Alexander Hristov recently spoke about reducing the carbon footprint through feeding on dairy farms at the recent Tri-State Dairy Nutrition Conference held in Fort Wayne, Ind.

Earning a spot as the second most important agricultural greenhouse gas in the United States aside from nitrous oxide, methane from manure management and enteric fermentation represented about 40% of all agriculture greenhouse gas emissions (GHG) in 2020, Hristov said. Also in 2020, beef and dairy cattle emissions accounted for 67% of all agricultural methane emissions compared to nitrous oxide from manure management, which only accounted for 4.6% of all agricultural nitrous oxide emissions in the United States. For this reason, research has mainly focused on depleting livestock methane compared to nitrous oxide.

Mitigation practices utilized in nutrition are determined by the type of production system (intensive versus extensive, smaller versus larger, and contribution of enteric methane to the carbon footprint of milk). Although manipulating feed ingredients and the diet are unlikely to deliver a large reduction in enteric methane emissions, feed additives such as macroalgae and 3-nitrooxypropanol (3-NOP) will create a more substantial reduction, said Hristov.

In a recent study at the Oskar Kellner Institute in Dummerstorf, Germany, 337 respiration chamber studies of different cattle breeds showed that digestible carbohydrates in the diet such as sugars, starch, and nitrogen free residuals can determine methane production. Hristov stated, “It is a well-established fact that enteric methane is generated because of fermentation substrates in the rumen. The more feed nutrients, specifically carbohydrates, are being fermented by the rumen microbes, methane production is expected to increase as the need to dispose reducing equivalents increases.”

It is proven that starch fermentation also has the ability to ferment more fiber, creating propionate in the rumen. While decreasing enteric methane emission intensity, raising the inclusion rate of starch in a dairy diet can serve as another methane mitigation practice. In a lactating dairy cow diet, by increasing the concentrate feeds’ starch concentration higher than the standard 20% to 30% that most dairy diets in the United States utilize, a reduction in enteritic methane yield can be achieved. Aside from seeing a potential improvement in milk yield, these interventions must be implemented with caution because farm profitability, depending on milk pricing (especially butterfat), could drop.

It is important to note that diet manipulation, such as improving forage quality and digestibility, elevates the proportion of concentrate feeds that are available to assist with minimizing enteric methane yield. Macroalgae and 3-NOP have been proven to reduce methane emission, although 3-NOP is backed by more research and more proven results. Further studies will be required to prove the effects of animal nutrition on manure composition, along with greenhouse gas emissions from manure storage and field application. If these mitigation practices provide consistent results, nutrition alone has the potential to showcase a 60% reduction in enteric methane emissions from the dairy industry, noted Hristov.

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May 6, 2024
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