Strategies to reduce methane emissions from Irish beef production
- Reducing slaughter age
- improved grassland management
- dietary supplementation with methane supressing compounds
- breeding of low methane emitting animals
- Methane is produced during the digestion of feed in the forestomach of ruminant livestock.
- Intensively-finished beef cattle offered a high-concentrate on average produce approximately 230 g of methane per day, equivalent to 22 g of methane for every kg of dry matter consumed.
- A suite of anti-methanogenic additives have been identified using an in vitro rumen simulation technique system. The most promising additives are now being assessed in sheep and beef cattle for their in vivo anti-methanogenic potential and effects on animal production.
- Low residual methane emissions (RME) beef cattle produce 30% less methane but maintain the same level of feed efficiency and carcass output as high RME animals.
- Achieving methane emissions reduction targets for ruminants will require a combination of strategies focused on suppressing methane output.
Plant matter consumed by ruminant livestock is digested by members of a microbial ecosystem residing in the rumen (forestomach). However, one group of rumen microbes, known as methanogens, produces methane, a wasteful end product of ruminal feed digestion. This accounts for nearly 60% of Irish agricultural related greenhouse gas (GHG). Methane is a GHG that is 28 times more potent to the environment than carbon dioxide.
Voluntary feed intake is the largest contributor to the quantity of methane emitted by an animal. Simply put, as an animal’s level of feed intake increases, more feed is fermented in the rumen, which both benefits the supply of energy and protein to the animal. It also elevates the supply of substrates to methanogens mainly hydrogen and carbon dioxide, leading to an increased synthesis of methane in the rumen. Indeed, a recently-completed Teagasc project, RumenPredict, established that for an indoor finishing ration, beef cattle produce, on average, 230 g of methane per day equivalent to 22 g of methane for every kg of dry matter intake.
The immediate implementation of steps laid out in the Teagasc Marginal Abatement Cost Curve (MACC), such as improved grassland management and technical efficiency, has the potential to deliver more than a 10% reduction in total on farm GHG emissions. Additional methane mitigation strategies are urgently required for the sector.
- Reducing slaughter age
- improved grassland management
- dietary supplementation with methane supressing compounds
- the breeding of low methane emitting animals
are some of the methane mitigation strategies currently being investigated by Teagasc. The most promising mitigation strategies, combined with those already identified with the Teagasc MACC, will be delivered on-farm via the Teagasc Signpost Programme.
Mitigation strategies currently under investigation
Research at Teagasc Grange is investigating strategies aimed at shortening the time it takes for animals to reach target slaughter weight and carcass fatness. Improvements to the average daily live weight gain of an animal, can not only be economically beneficial to the producer, but also reduces the quantity of methane emitted over the lifetime of an animal. Decreasing the age at slaughter from 27 to 24 months, has the potential to deliver a “methane savings” of in excess of 19 kg of methane per animal, over their lifetime.
- Improved grassland management
- the genetic selection of more efficient growing animals
- possibly the inclusion of clover and alternative species within the grazing sward
all have the potential to reduce the average slaughter age of Irish beef cattle, and are discussed in more detail in the following sections.
Low feed costs are the hallmark of pastoral-based ruminant production systems. Striking a balance between the quantity and quality of grass produced within the sward can be a challenge. As grass matures, the concentration of fibre increases within the plant which can reduce the digestibility of the grazing sward. A reduction in sward digestibility leads to a notable increase in enteric methane emissions by promoting the abundance of ruminal microbes associated with methane production. Both good grazing management and the incorporation of more digestible forages within the grazing system have the potential to promote greater average daily gain in cattle, therefore reducing days to slaughter and consequently the quantity of methane emitted over the lifetime of an animal.
Incorporating white clover into perennial ryegrass (PRG) dominated swards or including it in multi-species swards, decreases the chemical nitrogen requirements of the sward thereby reducing costs and nitrous oxide emissions. Some studies have demonstrated the methane reduction potential of both white clover and multispecies mixtures primarily as a result of higher sward digestibility. Furthermore, clover, plantain and chicory contain plant compounds which potentially have negative impacts on the activity of ruminal microbes involved in the production of methane.
Research at Teagasc Grange is currently investigating the implication of including white clover in PRG-dominated swards and in multi-species swards on the methanogenic output of beef cattle over the grazing season. Evaluating ensiled PRG/clover and multi-species sward mixtures over the indoor winter period is also being investigated. Laboratory-based experiments will examine the effect of multispecies compared with PRG dominant swards on methane emissions using the artificial rumen simulation technique (RUSITEC) system, and this will be followed by a large study with beef cattle.
The addition of fats and other lipids, containing high proportions of polyunsaturated fatty acids (PUFAs) i.e. soya oil and linseed oil to the diet have been proven to reduce the production of methane in numerous studies.
Seaweeds have been a traditional part of animal nutrition for centuries. More recently, the tropical red seaweed, Asparagopsis taxiformis has attracted worldwide attention following published reports of reductions in methane emissions of up to 80% when small quantities of this seaweed were added to cattle and sheep diets. The Irish climate is unsuited for the commercial production of Asparagopsis taxiformis. Researchers at Teagasc Grange are investigating the methane reducing capabilities of indigenous brown and green seaweeds. Over 30 seaweeds have being screened using the RUSITEC system, which simulates the rumen digestive process. The efficiency of a small number of seaweeds with apparent anti-methanogenic properties are currently being assessed in beef and sheep trials.
The synthetic compound 3-nitrooxypropanol (3-NOP) or Bovaer® (developed by DSM) has been widely researched in dairy and beef cattle with methane reductions of >30% observed. When consumed, Bovaer® is broken down into compounds that are already naturally present in the rumen, with its effect on methanogenesis immediate once ingested. It acts by inhibiting an enzyme which is required for the final step in methanogenesis and therefore stops the methane production process. However, the continued suppression of methane synthesis requires a constant supply of the compound in the rumen, with ruminal wash out of Bovaer® known to return emissions to near pre-supplementation levels.
This feed additive has been tested internationally under high-input intensive production systems with fewer research studies on livestock fed high-forage-based diets. In February 2022, the feed additive was approved for commercial use in the European dairy industry and was recently shown to reduce methane emissions by approximately 30% in beef cattle offered a grass silage-based diet at Teagasc Grange. Following the results of our study and others, the product will hopefully soon be licenced in Europe for inclusion in beef cattle diets.
Synthetic compounds such as oxidising methane inhibitors developed by industry partners are also being evaluated at Grange. To date, these additives have been assessed using the RUSITEC system, yielding promising results. The most promising formulations of these inhibitors are currently being fed to sheep and beef cattle to assess their anti-methanogenic potential and effects on animal productivity. A major global challenge is the application of feed additives during grazing. We are working closely with industry partners to develop slow-release formulations of their additive for pasture based systems.
The genetic selection of low methane emitting animals has long been advocated as mitigation strategy for the ruminant livestock industry. Recent data from Teagasc Grange and ICBF has highlighted a 30% difference in daily methane emissions between beef cattle of similar breed, age and diet. There is significant potential to harness the genetic variation for methane emissions that exists within the national herd, to bring about permanent and cumulative reductions in the methane output of future generations of livestock, via implementation of a low methane emitting breeding programme.
The breeding of more feed efficient and faster growing animals has great potential to decrease the lifetime emissions of beef animals. Until recently, the development of a national low methane emissions breeding programme had been limited due the lack of technology available to measure emissions from large cohorts of animals within a commercial setting. The advent of the GreenFeed Emissions Monitoring System (Fig. 1), makes it practically feasible to estimate methanogenic output of individual animals, both at pasture and indoor feeding conditions. Equally, the strong correlation between feed intake and daily methane emissions had traditionally limited the breeding of low methane emitting animals for fear of negatively impacting feed intake, which is a key driver of animal productivity, particularly in forage-based production systems. The recent collaboration led by Teagasc in partnership with ICBF and UCD has identified the residual methane emissions (RME) index as the optimal metric for disentangling the relationship of daily methane emissions with feed intake.
Figure 1. The first GreenFeed Emissions Monitoring System used to estimate enteric methane emissions at the ICBF Progeny Performance Test Centre in Tully (Co. Kildare).
Residual methane emissions can be described as the difference between methane emissions predicted for an animal based on its body size and feed intake and that which it actually produces. At the ICBF National Progeny Performance Test Centre in Tully, Co. Kildare, individual RME values were calculated for 282 crossbred beef cattle, steers and heifers undergoing a 90-day finishing period with detailed measurements of:
- methane output
- feed intake
- growth rate
- carcass output
Animals were ranked as high - undesirable and low - desirable in terms of RME. Low RME animals - efficient, produced, on average, 30% less methane, despite having the same feed intake, feed efficiency, growth and carcass output as their high - inefficient, ranking RME contemporaries. Results highlight the potential to breed more environmentally sustainable animals, while at the same time not having a negative impact on the animals’ performance, and indeed profitability. Further work is currently ongoing to study the underlying biology of the trait in an effort to potentially incorporate RME into the national breeding indices for Irish beef cattle.
Supressing the quantity of methane emitted by an animal and improving both the growth rate and feed efficiency of livestock, will be the most effective path towards achieving the agricultural sectors target of a 10% reduction in enteric methane emissions by 2030. While the reduction targets are challenging, research currently under way in Teagasc Grange, in collaboration with industry partners, aims to develop a suite of dietary and animal breeding methane mitigation strategies as well as production system modifications for better technical efficiency for the sector. The cost-effectiveness and overall impact of each methane mitigation action will be evaluated through the Teagasc MACC with the delivery of the most economical and promising mitigation strategies to the industry facilitated by the Teagasc Signpost programme.
Paul Smith1, David Kenny1, Emily Roskam1, Marie O’Rourke!, Alan Kelly2, Maria Hayes3, Stuart Kirwan1 and Sinéad Waters1
1 Teagasc, Grange Animal & Grassland Research and Innovation Centre, Dunsany, Co. Meath
2 University College Dublin, School of Agriculture and Food Science, Belfield, Dublin 4
3 Teagasc Food Research Centre, Teagasc Ashtown, Dublin