February 20, 2023

USDA awards researcher US$2 million to test feed additives' effect on methane emissions

The United States Department of Agriculture had awarded a US$2 million grant to  Alex Hristov, a professor of dairy nutrition from the Pennsylvania State University, to conduct studies determining whether supplementing the feed of lactating dairy cows with either 3-Nitrooxypropanol or a species of red seaweed reduces the amount of methane emitted by the animals in the long-term.

The award, coming through USDA's Natural Resource Conservation Service, will fund a three-year project that will be conducted with lactating dairy cows at different sites and with varied feed-management conditions. The study will extend over two lactations — almost two years — to determine the long-term effects of feed additives on mitigating enteric, or internal, methane production.

Hristov's research group in the College of Agricultural Sciences has been experimenting with supplementing the feed of high-performing dairy cows with additives ranging from seaweed to garlic and oregano oils to capsaicin from chili peppers in a nearly two-decades-long effort to reduce the amount of methane created by microbes in their rumens.

The supplements to be tested in this research project are very different, but in short-term studies, both have sharply reduced the amount of methane that results from the fermentation occurring in the cow's rumen. That process allows the animal to consume and utilise fibrous feeds and by-products that cannot be digested by humans or other, simple-stomach farm animals.

The methane inhibitor 3-Nitrooxypropanol (often referred to as 3-NOP, with the commercial name "Bovaer") was developed by DSM. 3-NOP has been approved for use as a feed additive in Europe and some Latin American countries such as Brazil and Chile but has not yet been approved by the US Food and Drug Administration.

Most, if not all, of the research with 3-NOP in dairy cows in the United States has been conducted at Penn State and some of the data were used for the European registration of the inhibitor. The compound acts on a key enzyme called methyl CoM reductase, responsible for the last step of methane synthesis in the rumen. In a 2021 review of Penn State's data published by Hristov's group, 3-NOP reduced enteric methane emissions by 25 to 29%

3-NOP is rapidly metabolised by the cow, and work at Penn State has demonstrated that it needs to be continuously supplied to the rumen with feed to effectively decrease methane production over the 24-hour feeding cycle, Hristov explained.

Dairy farmers are likely to adopt supplementing their cows' feed with 3-NOP, Hristov indicated, as it results in an increase in milk fat. "The energy of methane has to go somewhere," he said. "In our data — and we have the most data with dairy cows in the world — it seems like that energy is going toward milk fat synthesis, which is beneficial to the producer."

The red seaweed to be tested in this study is Asparagopsis taxiformis, which grows in some tropical ocean waters. In a 2021 study conducted by Hristov's research group, in trials with lactating dairy cows, Asparagopsis taxiformis decreased methane emission by up to 63% but also decreased feed intake and milk yield when fed at 0.5% of feed dry-matter intake. There were also questions about whether feeding the cows seaweed affected milk composition and taste.

Asparagopsis taxiformis appears to be an impractical source for a feed supplement, unless mass-produced in aquaculture conditions, Hristov pointed out. However, USDA wants Penn State to continue evaluating the seaweed's potential in long-term trials, given its efficacy mitigating enteric methane in short-term studies. If widely adopted as a livestock feed supplement, it cannot come from wild harvest, Hristov suggested.

"That would trigger an ecological problem that would not be an acceptable tradeoff," Hristov said. "Commercial ocean farming of the seaweed is the way to go, if this mitigation practice is to be widely adopted around the world."

He added that 3-NOP is currently the only substance that has consistently caused a significant reduction in enteric methane in cattle and not had unacceptable effects on milk production or quality.

"Penn State research has been a critical step in the approval process for 3-NOP around the world," Hristov said. "We have credibility because of our excellent facilities and our reputation for generating accurate, reliable data."

Where it is approved for use, 3-NOP is economical, so farmers can afford to use it, Hristov noted — it could be a game changer.

"But the question is, will its effect persist over a full lactation or several lactations, given the tremendous ability of the rumen microflora to adapt, and will the public accept it," he said. "It's a very small synthetic molecule that is metabolised very quickly and falls apart into compounds that are naturally present in the rumen of the cow. Consumer insight studies in the US, New Zealand and the Netherlands have shown considerable support for implementing 3-NOP."

- Penn State