Feed Additives Put the Brakes on Cattle Methane Emissions

17/03/2021 - 8 minutes

Research into how feed additives interact with the gut microbiome of cattle is paving the way towards a new strategy to tackle one of the main contributors to global warming.

Feeding over seven billion people comes with a massive carbon footprint. The agriculture sector demands the clearing of large areas of forests. Unsustainable agricultural practices such as monoculture, indiscriminate use of agrochemicals, and soil tilling contribute to greenhouse gas emissions. To add to it, food transportation or storage further generate emissions. However, the biggest culprit is a seemingly innocent one. It is cattle burping out methane — a greenhouse gas that stays in the atmosphere for much less time than carbon dioxide, but contributes more to global warming.

Cows emit methane every time they burp or pass gas. Their manure releases methane as well as other greenhouse gases such as carbon dioxide and nitrous oxide. A single cow produces up to 500 liters of methane in a day, and there are over a billion of them around the world. Agriculture is the main emitter of methane, with livestock being responsible for most of it. How do we tackle this? The search for answers takes us to the gut of cattle, where methane is produced in a process called enteric fermentation.

The stomachs of ruminant animals like cattle and goats are remarkably different from human stomachs. They have four different compartments. The first of these compartments, called the rumen, is where most of the action happens. It operates like a fermentation vat wherein microbes break down complex carbohydrates such as starch and cellulose, producing methane as a byproduct. In recent years, scientists have been researching how to control this process to reduce the production of methane. 

Plant extracts lower methane emissions

Phytogenics are plant-derived compounds that promote the growth of farm animals and don’t have antibiotic activity. The term was coined by the Austrian company Delacon back in the ‘80s. These compounds in plant extracts reduce the production of methane via one of several mechanisms, including inhibiting methane-producing bacteria or the protozoans that live in synergy with them, or boosting the metabolic pathways involved in using the hydrogen that would otherwise be turned into methane.

Thierry Aubert, who works at Delacon as Species Leader Ruminants, said that the company’s plant-based feed additive leverages all three. “It has an effect on fermentation with stimulation of the starch degradation in the rumen, a direct effect on protozoa and archaea methanogens, and mitigation of dihydrogen by sulfate reducers found in some plant extracts,” Aubert told me.

Swiss biotech company Agolin has developed a blend of essential oils as a feed additive for reducing methane emissions. “When it is included in dairy and cattle feed at a rate of one gram per head each day for adult animals, our feed additive has been shown to influence the production of methane in the rumen and thereby its release to the environment,” said Kurt Schaller, Agolin CEO. However, it is not yet clear if this effect is due to its action on microbes in the cattles’ gut or a change in the fermentation reactions they perform.

A recent analysis suggests that it is likely that Agolin’s feed additive does a bit of both. “We discovered a positive shift of the rumen microbiota after a few weeks’ adaptation time, namely a significantly larger rumen bacteria population and a reduced number of protozoa when Agolin’s feed additive was fed to cows,” Schaller added.

A feed additive from Mootral, another Swiss biotech, consists of bioactive compounds from garlic and citrus flavonoids. It acts directly on the archaea responsible for methane production, causing a sharp decline in the numbers of many methane-generating species without negatively impacting the fermentation processes. Unlike the feed additives from Agolin and Decalon, Mootral’s is awaiting approval for commercial use.

For all of these phytogenic additives, there is a huge gap in the methane reduction seen in laboratory experiments versus those achieved in the field. While improving the action of feed additives is critical to bridge this gap, the challenge could lie in animal behavior as well. Cows can be picky eaters and will not eat if the feed additive is not palatable to them. In addition, different feeding regimes can affect the composition of the gut microbiome.

According to Ruchita Khurana, Mootral’s Scientific Manager of Animal Health, “the rumen with its microbiome is still an area that is yet to be fully understood scientifically. We try to focus on running trials in a variety of farm setups, breeds, and feeding regimes to enable us to evaluate the impact of Mootral in different farm realities.”

Seaweed offers a circular alternative

Coastal communities have used seaweed as livestock feed for millennia. In recent years, several studies have demonstrated the methane-reducing potential of this practice. One of these studies demonstrated up to a 99% reduction in methane production when Asparagopsis taxiformis, a red algae species, is added to animal feed. The seaweed synthesizes and stores bromoform, a potent inhibitor of the methyltransferase enzyme required for methane production.

Swedish startup Volta Greentech utilizes A. taxiformis to produce a feed supplement for cows. The company employs a land-based production system and vertical bioreactors to maximize seaweed growth. By recirculating the seawater and using waste heat from nearby industries, the startup lowers the emissions involved in the production stages as well. 

Irish startup DúlaBio, on the contrary, makes its feed additives with a blend of native seaweeds. The company contributes to further emission reductions by promoting regenerative seaweed farming and rural bioeconomy.

Both Volta Greentech and DúlaBio report a nearly 80% reduction in methane emissions in the field. While far from the 99% reduction demonstrated in previous studies, this is considerably higher than the maximum of 38% reduction reported for phytogenic additives. However, the challenge for seaweed lies in the potential economic and environmental impacts of seaweed cultivation at scale.

Current seaweed production systems need to be massively scaled up to grow enough seaweed for it to be a viable method to tackle methane emissions from livestock. There is also the risk of cattle building up high levels of iodine on a seaweed diet. This makes it a safety concern for humans too as high levels of iodine can affect thyroid health and might as well be keeping some biotech companies away from innovating in seaweed-based additives. In addition, seaweed can accumulate heavy metals such as lead and mercury, and bromoform is classified as a probable human carcinogen.

“Red seaweed has a good potential in terms of methane mitigation. But we have some rules in Europe in terms of iodine, heavy metals, and bromoform — one of the main components responsible for the methane reduction — in the diet,” Aubert commented.

Lastly, natural selection poses a threat of lowered efficacy of methane reduction with time. Just as human pathogens become antibiotic resistant with prolonged exposure, ruminant microbes might evolve defense strategies against feed additives that reduce their numbers. If that happens, biotech companies will need to identify new mechanisms to target.

Why should farmers care?

Unlike other human activities, the environmental impact of agriculture isn’t visibly evident. Moreover, many farmers don’t trust the mainstream media or environmental organizations. In developing countries where most farmers represent the poorest of the poor, the burden of reducing greenhouse emissions should not be on them. What, then, is the incentive for farmers to adopt practices that reduce methane emissions? 

For one, they are the ones most impacted by climate change as floods, droughts, and wildfires wreak havoc on their farms. But for the widespread adoption of particular solutions like feed additives, there has to be a more visible benefit to the farmers.

The methane expelled by the cows represents a waste of energy. Consequently, feed additives that reduce methane emissions could lead to better feed utilization. If biotech companies can market these additives with a demonstrable benefit to cattle productivity and health, it could go a long way in mitigating methane production in agriculture. For instance, by lowering ammonia emission and nitrogen losses, Delacon’s feed additive increases milk production by 1.7 liters per cow per day.

Going forward, the implementation of this technology may benefit from carbon accounting solutions aimed at larger institutions that interact with farmers. According to Eileen Rüter, Director of Business Development at Mootral, the company is developing a carbon credit model to lower its production costs while making emission reductions fully traceable. 

“Our business model for our first commercialization phase relies on incentives that are given to the farmer by processing companies, retailers, or governments to cover the costs of the product. We are actively engaging with several such companies and governments to connect the dots.”

 

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