Written by Lewis Wallis, Edited by Charlotte Pugsley and Anna Ivanus.
The UK Government has recently launched a “call for evidence” to gather information about how animal feed products could be used to reduce methane emissions [1]. Through this initiative, stakeholders can help contribute to future policy that shapes the type of animal feed we produce, aiming to reduce the environmental impact of livestock production.
But what are methane-reducing feed products and how do they benefit the environment?
Methane, otherwise referred to by its chemical formula CH4, exists all over the world. It can be found deep under the seafloor and as high as the Earth’s atmosphere. Atmospheric methane is of great concern, as it is one of the most potent greenhouse gases contributing to global warming.
To give an idea of the impact that methane has on the environment, let’s compare it to carbon dioxide (CO2), another significant greenhouse gas. In the last two decades, methane had 80 times more warming potential than CO2 and so far, has accounted for approximately a third of global warming since pre-industrial times [2]. It is concerning that this figure is increasing at the fastest rate since records began. Atmospheric methane still suffered an increase despite the world being brought to a standstill during the pandemic. Therefore, it is important that reduction of atmospheric methane has been highlighted as a key issue for the survival of our planet, and a global pledge was made at the COP26 in Glasgow by more than 100 countries, including the UK, to cut emissions by 30% by 2030 [3].
Livestock production of methane (from manure and animal release) accounts for roughly a third (32%) of human-related methane emissions [2]. How do animals make up such a large contribution? It all takes place in the gut. Plant material fed to the animals is broken down by bacteria sitting in the gastrointestinal tract, leading to the subsequent production of methane in a process known as methanogenesis. After production, the gas must go somewhere and is eventually released through ‘burping’ or excretion (Not the most pleasant thought, I know!).
Feed materials are animal or vegetable products that are minimally processed and used to provide animals with appropriate nutrition. By providing animals with more nutritious feed, they can become larger and healthier, hence contributing to a more efficient livestock production process. Such feed materials can, with the relevant authorisation, contain feed additives.
Feed additives, added to animal feed or their water supply, improve the characteristics of either the feed product or the animals that consume them. Some examples include:
Feed additives can also be authorised if they help reduce the negative impact that the animal has on the environment, as is the case with methane-reducing feed additives. As outlined in the UK Government’s “call for evidence”, a methane-reducing feed additive is a product that, when added to animal feed, can reduce the production of methane after consumption. Methane-reducing feed products interact with microorganisms in the stomach of ruminants, leading to lower levels of methane production. A range of products has been identified as potential additives, including seaweeds, essential oils, and probiotics. However, the first to be approved was the chemical compound 3-nitrooxypropanol (3NOP).
This first methane-reducing feed additive was authorised by the EU in April 2022. Until 3NOP, no feed additive designed for its environmental benefits had ever been approved. While not yet authorised for use in Great Britain, an application has been submitted to the relevant authorities (Food Safety Authority (FSA) and Food Standards Scotland (FSS)) and is currently under consideration. The European Food Safety Authority (EFSA) provided an opinion before the approval, concluding that 3NOP was efficacious and safe for animals and consumers, and did not affect the quality of the milk or meat products.
Microorganisms that produce methane (CH4) use an enzyme to kick-start a reaction between carbon dioxide (CO2) and hydrogen (H2). The newly authorised additive 3NOP can reduce methane production by interacting with this enzyme and inhibiting its activity, which reduces methane production by more than 25% [4].
A potential additive that could be approved in the future is Asparagopsis, commonly known as red algae. After harvesting from seaweed farms, Asparagopsis is preserved by drying at very low temperatures, helping to maintain its bioactivity. The compound that gives the red algae methane-reducing properties is bromoform (CHBr3), which can, in a similar mechanism to 3NOP, bind to and inhibit a key bacterial enzyme responsible for methanogenesis [4]. A recent meta-analysis confirmed that feeding Asparagopsis to cattle can reduce methane production by 37% [5]. In two more recent studies, published after the meta-analysis, an even greater methan reduction (of up to 80%) was found [6, 7], indicating that this additive could be even more potent than expected! Although this reported efficacy is higher than that of 3NOP, the use of Asparagopsis has less supporting data, and therefore further study is still required. Furthermore, another barrier in its development lies in the upscale, as seaweed farming and the production process would need to be scaled up to ensure the affordability of commercialisation.
Ensuring that their use is profitable for livestock managers is of fundamental importance to the introduction of methane-reducing feed additives and could prove to be a barrier to their adoption. Until their supply increases, a policy could be introduced that aims to incentivise the widespread use of any approved additives.
A survey-based assessment found that stakeholders (additive manufacturers, feed manufacturers, and livestock managers) from industry are not currently prioritising methane-lowering feeds [4]. However, over the next 5 years, the development of methane-reducing feed additives is expected to continue, as emphasised by the UK Government. Although no silver bullet exists to solve the problem of methane emissions, feed additives appear to be a viable option to support the longevity of our planet, whilst still continuing to feed our growing world population.
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