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Beef and Sheep Production

A significant source of GHGs from UK agriculture.

GHG emissions from beef and sheep production are a very significant source of GHGs from UK agriculture.

Approximately 60% of the UK's farmland is grassland; of which just over half is permanent pasture and around 40% of which is unimproved rough grazing.

There is therefore clearly a role for beef and sheep production in the UK from this substantial land area that is unsuitable for cropping –reduced stocking rates would immediately reduce overall GHG emissions from your farm/UK but not overall if the beef/sheep was produced elsewhere.

The majority of GHGs from beef and sheep are emitted as methane (CH4) – this is a by product of the ruminant's digestive process as it converts forage to useful energy and accounts for approximately 60% of all GHGs for beef and 70% of all GHGs for sheep.

The other significant GHG emission is nitrous oxide (N20) (accounting for 25-30% of all GHGs for beef and sheep) which is emitted mainly as a result of fertilizer and manure applications.

The use of diesel and electricity and carbon dioxide (CO2) emissions are less than 10% and so relatively unimportant compared to the other emissions.

Mitigation strategies:

Improving overall efficiencies of the flock/herd:

This is the route recommended by the major industry organisations and, where possible to implement, will benefit the farm business as well as reducing farm GHG emissions.

The Scottish Agricultural College have put numbers to a couple of immediate efficiency indicators in beef production systems:

  • Reducing calf mortality rates by 5% will reduce GHG emissions by 10% per kg carcass weight.

  • Increasing the energy content of ensiled grass by 1MJ/kg DM will improve feed quality and DM intakes resulting in a reduction of GHGs by approximately 6% per kg of carcass weight.

  • Teagasc, the Irish research and extension service, estimate that there are differences of over 3x between the 'worst' and the 'best' beef farms across the range of production systems. They calculate that an extension in the grazing period by two weeks either side of housing cattle can reduce GHG emissions by over 5% due primarily to the reduction of slurry stored and the higher digestibility of grazed grass compared to conserved forage resulting in better live weight gains. They are currently working on a 'carbon navigator' tool that will be used by extension workers to assess current KPIs and plot improved efficiency targets for farms to aim at that can be quantified.

  • Improved health status, improved feed conversion efficiency and any management changes to increase live weight gain will have corresponding benefits to all aspects of the farm business.

  • The opportunities for diet modification are far less than with dairy herds as nearly all beef and sheep are extensively reared with little concentrate inputs. However incorporating legumes (and where possible high sugar rye grasses to increase the feed value of the grass will also benefit both bottom lines.

  • The area for greatest GHG reductions is around the application of manures and fertilizers. Any reduction in the use of fertilizers will have a significant effect as N2O is the most potent of all GHGs. Careful application techniques for manures and careful timing of all applications to avoid putting on more nutrients than can be taken up by plant growth or taken into the soil organic matter will significantly reduce GHG emissions. It is equally important to not apply nutrients to waterlogged soils as N2O emissions will be very high in these conditions – and you're losing nearly all the Nitrogen that you're putting on to feed the pasture.

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Replacing nitrogen fertilizers with legumes:

Legumes such as clover have the ability to fix nitrogen and replace the need to apply artificial nitrogen. Introducing clovers, or other legumes, into established permanent pasture requires attention to detail but is relatively straightforward to achieve and once established they can produce similar amounts of forage to fertilized grass without the cost and the GHG emissions. Specialist advice can be found by talking to seed suppliers.

Manure storage:

There are a number of studies on how different storage techniques for solids and slurries affect GHG emissions with conflicting results.

Methane producing bacteria thrive in anaerobic conditions and higher temperatures therefore aerating slurry stores, regularly turning muck heaps and emptying the slurry/manure store before the summer will reduce CH4 emissions. However ammonia and nitrous oxide losses are generally higher in aerated conditions - one study found losses of N2O to be double from aerated slurry stores than un-aerated stores. It is agreed by all researchers that using a trailing shoe for slurry applications reduces GHG emissions (and nitrogen losses) as immediate soil contact reduces losses of ammonia with consequent reduction in N2O emissions.

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Mob stocking:

Mob stocking is a technique that is being developed in many countries as an alternative pasture management system for beef. It runs counter to the conventional grazing strategies which encourage regular and frequent grazing. In mob stocking the intervals between grazing are 2- 3x as long, with the grass much more matured when grazed. The cattle are only on any area of grass for a few days maximum, at very high densities, and trample a significant proportion of the grass into the soil. This 'wasted' grass increases soil organic matter content with a corresponding sequestration of carbon. See soil sequestration section for more details.

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