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9.12.14 Theme of the month: Livestock Diets

8th Dec 2014

With the festive season upon us, and with us all turning our attention to the meals that we will be having towards the end of the month, here at FCCT we thought that we would focus on livestock diets and the effect that diets have on greenhouse gas emissions.

Animal production is a significant source of GHG emissions both in the UK and worldwide.  The main processes that contribute to direct non-C02 greenhouse gas emissions from livestock are enteric fermentation and manure decomposition.  These processes are the largest sources of methane and nitrous oxide from any animal production system.

Enteric fermentation

So how does it work?  Ruminants digest fibrous plant materials by fermenting them in their rumen (which contains a complete mix of microbes).  In this mix of microbes are methanogens, which produce methane as a by-product expelled in the breath when the animal burps.  Monogastric animals such as pigs and poultry produce much less methane than ruminants.  Methane production captures the hydrogen produced during fermentation.  There are however competing fermentation pathways in the rumen that do not produce methane.  There are a variety of dietary and other possible approaches to promote alternative fermentation pathways to reduce methane emissions.

Quantifying the emissions

There are various figures quoted as to the amount of methane emitted due to enteric fermentation, and the range is somewhere between 12,800 - 17,600 MTCO2e of methane annually in the UK.

Improved feed formulation

Methane production in the rumen is driven by the content of the food supply.  Fermentation with higher proprionate concentrations in the rumen have been widely associated with lower levels of final methane emissions.  There are a variety of nutritional management strategies to bring about reductions in enteric methane that have been suggested and these will be discussed in more detail.

Dietary strategies to reduce emissions

There are various strategies advocated to reduce methane emissions which will be discussed this month.  They include:

  • high protein
  • high sugar
  • high quality forage
  • high starch
  • oils and fats
  • supplements

Final thoughts

It has been suggested that ruminant livestock production and consumption makes a large contribution to GHG emissions, which can be attributable to food production.  It is important to remember however that ruminant livestock play an important role in global food security as they can convert the ligno-cellulosic and non protein nitrogen compounds found widely in plants, but indigestible to all monogastric animals including man, into high value protein for human consumption.  Future ruminant agriculture will need to capitalise on this important benefit.  Ruminant agriculture therefore has a key role to play in maintaining and enhancing the provision of quality proteins and essential micronutrients in man's diet, provided that the challenge of reducing GHG emissions and methane in particular can be successfully addressed.