Enteric emissions are the greatest contributor to the on-farm carbon footprint of milk.

Lee karen
Managing Editor / Progressive Dairy

Methane produced by enteric fermentation or the process that enables cows to eat and break down forage and byproduct feeds amounts to 35% of a dairy farm’s greenhouse gas (GHG) emissions, according to life-cycle analysis research on U.S. milk production.

Achieving a win in this area will certainly move the industry closer to the overall goal of carbon neutral by 2050.

Dr. Juan Tricarico, vice president of sustainability research at Dairy Management Inc. (DMI), says wins are not a result of the final score but of the plays made in the game. When it comes to reducing enteric emissions, we can start with the plays we know work and are available right now.

Reformulating diets

“Feeding cattle is one of the biggest elements of how farmers care for cattle,” Tricarico says. “In fact, feed going through a farm represents the largest input in terms of mass and also dollars.”


The types of forages and feed ingredients in a cow’s ration has a direct effect on the animal’s enteric emissions.

Tricarico is reviewing scientific literature to see if more energy-dense diets that include more lipids (fat) and concentrates (starch) could be fed to reduce enteric methane emissions.

In a recent article for Progressive Dairy, Michael Miller with Trouw Nutrition pointed out cows fed forages with higher fiber digestibility and lower indigestible fiber emitted less methane while increasing their feed intake and producing more milk.


The sustainability advantages of feeding byproducts to dairy cows goes beyond GHG emissions, as it is a way to recycle unwanted plant parts into nutritious, consumable milk.

“[Dairy] animals actually consume quite a large amount of byproducts in their diets,” Tricarico says. His recent research shows U.S. milking cows consume, on average, 8.2 kilograms (18 pounds) dry matter (DM) of byproducts daily.

These byproducts supply 37% of energy and 54% of protein fed to lactating cows. By doing so, they replace forages and concentrates needed in the ration. This reduces crop production needs and the GHG emissions associated with growing the crops.

For instance, corn grown for the purpose of making ethanol can find its way to a dairy farm as distillers grain. The original purpose of the crop has been met and yet the remaining biomass can be repurposed as feed.

Seventy grams of CO2-eq GHG are emitted in the forms of enteric methane, manure methane and nitrous oxide per kilogram of byproduct (dry matter) fed to U.S. milking cows to partially replace forages and whole grains. At the same time, the nutrients from the byproducts are recycled into the milk produced.

This is lower and more beneficial than other methods of processing this unavoidable food waste. Tricarico’s research found composting generates 328 grams of non-CO2 GHG while recovering some of the nutrients as soil amendments. Landfilling generates 3,448 grams of non-CO2 GHG and incineration 31 grams of non-CO2 GHG, but in both scenarios all nutrients are lost.

Tricarico says, “Feeding these agricultural byproducts to the animals is the best thing to do if you’re trying to have a circular economy, if you’re trying to make the best use of these materials because they’re rich in nutrients.”

Feed Saved trait

Late last year, a new play was added to the enteric emission reduction playbook. This play is not used at the feedbunk but instead in genetic selection.

With its Dec. 1 evaluations, the Council on Dairy Cattle Breeding (CDCB) released the Feed Saved trait. This trait is composed of two parts: when a cow can produce more milk per unit of bodyweight and when a cow can eat less than expected based on its milk production, bodyweight and bodyweight change (residual feed intake or RFI).

“Whenever these traits are developed with one objective in mind, they need to go into a balanced approach in the form of an index that balances out the multiple objectives farmers and the industry have,” Tricarico says.

The August revisions to Net Merit incorporated Feed Saved and two other traits to target maximum lifetime profitability.

As a new trait, researchers will continue to monitor Feed Saved to ensure gains in feed efficiency are not accompanied by losses in health, fertility or longevity.

“Eventually, as this particular trait goes in, we’re going to be selecting cows that eat less feed,” Tricarico says.

“In general terms, I would expect that in a few years the requirement for feed as a whole, in the aggregate, would actually go down. Cows would need less feed to produce the same amount of milk,” he reasons.

This will not only affect enteric emissions but also the emissions associated with growing less crops in the field.

In addition to the current playbook, Tricarico says there are two big plays being developed.

Low-methane-emitting cows

On the genetics front, Tricarico says, “We’re exploring this idea of identifying and breeding cows that naturally produce less methane.”

If that is the case, dairy producers could select for and breed low-methane cows to reduce the enteric emissions from their herd.

Feed supplements


Photo by Mike Dixon.

Another play receiving a lot of attention is feed supplements that reduce methane from enteric fermentation.

Two supplements, 3-nitrooxypropanol (3-NOP) and red seaweed, when fed to cattle have been shown to directly inhibit enteric methane emissions.

Research has shown the effectiveness of 3-NOP is about 40% in dairy, and trials for red seaweed had even higher levels of efficacy, from 43% to 67%.

These supplements are not currently approved for use in the U.S., and their costs are not yet known.

There are many factors that play into the adoption of feed supplements in the food chain, so Tricarico is consulting with all stakeholders. This includes supplement suppliers, scientists who are evaluating the supplements in a research setting, dairy cooperatives, the brands that purchase milk and consumers.

He is doing this to understand what is necessary for the dairy value-chain to have confidence that a supplement fed specifically to reduce enteric emissions is efficacious, is safe for the animal to consume and is safe for humans to consume food from those animals.

Tricarico also wants to be sure the trade-offs resulting from feeding these supplements are reasonable. For example, that milk production is not going to drop, the milk is not going to taste off, the supplement won’t be too costly and that it is easy to implement on the farm.

“It’s important, I think, for everybody to know the industry is going through a consultation process and a conversation is starting to emerge, so that eventually when some of these feed supplements become commercially available, we can all ask intelligent questions and make decisions from an informed basis,” he says.

Each of these plays have important contributions to make toward winning the industry’s goals set forth in the Net Zero Initiative.

“We’re going to win by feed supplements. We’re going to win by breeding cows better. We’re going to win by using byproducts,” Tricarico says.

He adds, “All of these are basically plays that allow the farmer to reduce their footprint and use less resources to provide the nutritious milk the public demands.