With the environmental impact of livestock farming under increased scrutiny, what can farmers do to be as sustainable as possible?
Meat production has many benefits – including biodiversity, soil fertility, and nutrition – but it also comes with environmental challenges.
In the UK, 56 per cent of farming’s greenhouse gas (GHG) emissions are methane (mainly belched out by ruminants), accounting for about 5.5 per cent of the country’s total, according to the Department for Business, Energy and Industrial Strategy.
About 12 per cent are carbon dioxide (mostly from transport and production processes) and 31 per cent nitrous oxide (from urine and dung), the latter turning into ammonia, a significant contributor to air pollution and related health problems.
However, best farming practices can help reduce these, says Liam Sinclair, professor of animal science at Harper Adams University.
Prof Sinclair says: “If you are improving animal performance then you are reducing environmental impact.
“Faster growing, healthier animals produce less methane, excrete less nitrogen and phosphorus and, therefore, have a lower impact.”
Returning to more mixed farming systems, managing waste properly, maintaining healthy soils, and introducing home-grown forage, mixed grasslands and more trees, can all contribute too.
While many will also reduce input costs, some carry additional costs, however, so consumers or government policy will ultimately decide how sustainable farmers can be, say scientists.
Reduce carbon emissions from imported protein by growing more home-grown sources, such as peas, oats, beans, and legumes.
In grazing livestock, forage legumes which fix nitrogen – such as red clover and lucerne – will reduce the need for artificial fertilisers, lowering nitrous oxide emissions.
Avoid overfeeding protein to cattle though, as this will cause excess nitrogen excretion and the subsequent release of ammonia, says Prof Sinclair. Reducing a dairy cow’s protein intake to about 16 per cent (UK average is 17-17.5 per cent) should reduce emissions while ensuring it get what it needs.
Protein from legumes can be too available to rumen microbes, so to achieve the right balance, beef, dairy and sheep farmers should get their forage analysed and diets properly formulated. Dairy farmers can also
get milk urea levels analysed, advises Prof Sinclair.
Higher quality forages (low in fibre, high in digestible matter) and maize silage will reduce methane production in the rumen. Adding micro-algae may also reduce methane emissions, although this could impact the taste of meat and dairy products.
Supplements containing 3-nitrooxypropanol have been shown to reduce methane production by 30 per cent and should be available next year, says Prof Sinclair.
Ensure beef cattle and sheep achieve as high a liveweight gain as possible - aim for 1 kg/day in beef animals.
Monitor this in tandem with grass cover using a plate meter.
Introduce grassland budgets, consider new varieties, and have a reseeding policy to maximise weight gain.
To avoid excess nitrogen or phosphorus applications, only apply when plants are growing, make use of organic manures and analyse these along with your soils, says Prof Sinclair.
To avoid ruminants getting bloated on clover, feed hay before turning onto a new field, advises Richard Young, mixed farmer and policy director at the Sustainable Food Trust.
Soils may take a while to adjust to legumes, but farmers can ask their merchant to inoculate non-native
seeds (lucerne and sweet clover) with rhizobia bacteria to help get them going, says Mr Young.
Incorporate agroforestry and silvopastures (trees, forage plants and livestock) into systems, suggests Mr Young.
Planting more oak trees such as in hedges, will lock away carbon for hundreds of years. Around 400 species
of insects, birds and lichen live in oaks.
Trees and hedges also help provide shade and shelter for livestock - particularly important as climate change brings more extreme weather.
Farmers should try not to trim hedges every year, so birds have berries going into winter.
Creating varied grasslands will also help animal species and microbes both in the soils and outside.
Legumes will provide nectar when other sources are scarce, while deep-rooting herbs like chicory can help lock up carbon deeper and guard against drought and floods.
Animals which age faster and reach slaughter sooner will consume more resources, says Mike Coffey, professor of livestock informatics at SRUC, but this is offset by the reduction in days alive and head of animals needed to produce the end product.
“Some crude estimates show if the whole beef herd reduced its age at slaughter from 28 months (the mean now) to 14 months it would save around a third of emissions,” says Prof Coffey.
Farming has so far used genetics to select for health, welfare, and production traits, which have helped reduce GHGs per product, says Prof Coffey.
But science could go further to create a phenotype for cattle with lower methane production, although it is some way off.
Prof Sinclair, advises farmers to use key performance indicators (KPIs) to improve performance.
“A suckler herd should aim to produce one cow a year, and calve within a nine-week window,” he says.
“Replacement beef and dairy heifers should calve at two years old, not three, in terms of efficiency.
“Select a beef bull with high EBV for 200 and 400-day weight, and muscle depth,” says Prof Sinclair. In dairy, look at the profitable lifetime index, which is mostly based on fertility and longevity.”
Increased biosecurity and herd health will also improve performance, says Prof Andrea Wilson, acting head of the Roslin Research Division of Genetics and Genomics.
“Apply vaccinations, and purchase animals with high genetic health index to mitigate disease risk. Infected animals grow slower and produce less,” she says.
A culling policy, worming programme, and optimum stocking rates, should also all help ensure
a healthy herd using resources most efficiently.
Ammonia and methane emissions can be reduced by better management of slurry, manure and digestates. Minimising the surface area of exposed organic matter is key.
If possible, farmers should cover slurry pits and silos with a roof, floating cover, or if this is too costly, floating bodies such as plastic, straw or bark can be used.
Reducing slurry channels, and having cooler outdoor storage instead of underfloor storage, will also help. An anaerobic digester could also turn manure into renewable energy.
In some areas, pig and poultry units have more control over managing waste, such as ammonia released from housed units, says Prof Sinclair.
But farmers should avoid mixing waste when clearing sheds as much as possible.
For the same reason, spread livestock manure/ slurry using trailing shoes or dribble bars, advises Prof Sinclair, to ensure more nutrients enters the soil, and minimise ammonia being released.
“Analyse your slurry for nitrogen levels to work out whether further nitrogen fertiliser is needed and exactly how much - to reduce excess applications,” he says.
“Get soils analysed for their phosphorus content and avoid applying phosphate when not necessary too.”
Manure and slurry should be incorporated within a few minutes – this could avoid up to 90 per cent ammonia losses in the field, advises the EU’s Clean Air Farming project.
Consider diluting liquid manure by at least 50 per cent, such as via irrigation systems.
Acidifying slurry from a naturally high pH value to a neutral level, using sulphuric acid, can reduce ammonia emissions by at least 50 per cent.