“Novel feed additives can reduce CH4 production in the rumen, but many are not yet available or not yet proven on UK farms,” according to a new publication from Centre for Innovation Excellence in Livestock (CIEL).
Work is ongoing to bring dietary methane inhibitors to the UK market and to develop delivery mechanisms that are better suited to grazing systems and less dependent on concentrate feeding, noted CIEL. “The challenge of adopting such inhibitors into mainly forage-based systems needs to be addressed urgently for the UK.”
The organization commissioned an independent consortium of expert scientists from the Agri-Food and Biosciences Institute (AFBI), Queen’s University Belfast, Scotland’s Rural College (SRUC) and Rothamsted Research to deliver the report.
The resulting publication, Net Zero & Livestock: How farmers can reduce emissions, looks at key strategies that livestock farmers can adopt now to reduce their carbon footprint and drive down net emissions.
For each species, key mitigation approaches are described and their impact modelled.
The report follows on from Net Zero Carbon & UK Livestock, produced in 2020, which established benchmarks for a range of UK farming systems.
Feed and forage focus
Efficiencies around feed, forage and nutrient management are particularly pertinent for UK livestock production, noted the latest review.
“Increasing productivity per animal while reducing input costs, and maintaining overall productivity at the same level, is something that can be done now. Farmers can focus on aspects such as age at which females first breed and their productive lifespan; the number of offspring produced and their growth rate; and rate of milk or egg production.”
With regard to pigs and poultry, the publication noted that while their impact on UK emissions is smaller than ruminants, their carbon footprint is greatly influenced by the source of feed ingredients.
“The effect of land use change (or not) associated with the protein ingredients within pig and poultry diets had the most significant impact on the carbon footprint within the farm case studies. For example, the carbon footprint of the pig and broiler farms modelled increased by over 100% when the protein ingredients were associated with land use change, compared to when no land use change was considered. It is noted that home-grown ingredients will be of most benefit if sourced from ‘non-land use change’ practices.”
Soy from ‘non-land use change’ practices grown in other countries should not be considered negatively, it stressed.
The percentage contribution of each livestock type in the UK to the total global warming potential (GWP) as reported by the 2019 UK National Inventory
Increasing starch content in beef and dairy cow diets
The ruminant sector, especially beef and dairy, represent the main contributors of GHG emissions from UK livestock production, with the report stressing the importance of new technologies such as rumen methane inhibitors and wide-scale adoption as being critical to reduce emissions further in those sectors.
Beyond the use of methane inhibitors, other nutritional approaches that might help the UK dairy and beef sectors to achieve net emissions include increasing starch and concentrate proportions in the diet, within recommended guidance levels, to reduce methane (CH4) production per unit of feed intake. Depending on baseline diet, management and animal factors, this strategy could increase milk output in dairy cattle and should increase liveweight gain in beef cattle, reads the report.
The authors maintain that wider environmental considerations associated with carbon footprint of feed components and farm nutrient balance must be considered, and not just the financial impact.
Genetic improvement could also help reduce emissions in the dairy and beef sectors if focused on component traits, such as productivity relative to cow size, feed efficiency, fertility, longevity, or health. Genetic information for growth and carcass traits should be used in both dairy beef and suckler beef systems, found the report. “This should be part of farm decision making now, to deliver long-term emission reductions.”
Methane inhibitors
The report outlines emerging dietary methane inhibitors.
Nitrate
Nitrate, it noted, is a feed additive that intercepts the methanogenesis process and therefore reduces enteric CH4 production. “However, nitrate poisoning of ruminants and rumen microbes has been reported, in particular through inhibition of fibrolytic bacteria and methanogens. Furthermore, feeding nitrate might increase the concentration of nitrate and nitrite in milk and urine. Nitrate tastes bitter which lowers the palatability of nitrate-based diets and may cause lower feed intake, leading to lower levels of production.”
3-NOP
The use though of nitrate as a feed additive in precision indoor feeding systems has shown promise, reads the publication. Its use within grazing or non-total mixed ration (TMR) systems presents a major challenge, it added. “More work is required on the use of nitrate as a CH4 reducing mitigation to manage any unintended detrimental impacts on the animal and its outputs.”
3-NOP (3-nitrooxypropanol) is a novel and specific small molecule that can stop the action of an enzyme called 'methyl-coenzyme M reductase' (MCR), according to the report.
“This enzyme is key in the last step of the process which generates CH4 in the rumen of animals. 3-NOP has been found to reduce CH4 from ruminants, although the dose and application strategy needs to be tailored depending on the types of animals. Currently, 3-NOP can only be used in conjunction with concentrate feeding, with only a very small amount (100-200mg/kg dry matter per day) needed.”
Studies have found long-lasting improvements in animal performance such as increased production of milk fat or milk protein, said the authors. As a feed additive, 3-NOP requires regulatory approval by various countries.
Seaweeds
Seaweeds provide a large group of essential nutrients as well as numerous secondary plant compound, with some of these secondary compounds found to reduce CH4 emissions when offered to cattle and sheep.
“Much work continues to identify raw seaweed products as well as the active compounds responsible for the reduction in CH4 emissions. Certain seaweeds also contain omega-3, omega-6 and other polyunsaturated fatty acids. Algae-based feeds may improve the fatty acid profile of diets, increase the fat content, and reduce somatic cell counts in milk. However, seaweeds may also contain inorganic elements and heavy metals that, at high levels, may cause toxicity in animals and humans. As such, work on seaweeds continues, but the use of the active compounds contained within them shows promise to be a future key mitigation strategy to reduce emissions from cattle and sheep.”
