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Methane Research has Implications for Irish Dairy

08 October 2008

UK - Research undertaken by Agri-Food and Biosciences Institute (AFBI) at Hillsborough has demonstrated that methane emission from dairy cows accounts for on average 6% of total energy intake.

The AFBI Hillsborough Ruminant Nutrition Team
Photo: AFBI

The AFBI Hillsborough Ruminant Nutrition TeamCurrent concerns relating to methane emission are its impact on global warming as a major greenhouse gas. Although methane concentration in the troposphere is very low in comparison with carbon dioxide (1.7 verses 350 parts per million), the global warming potential of methane is 21 times that of carbon dioxide. Methane is therefore responsible for approximately 20% of global warming, whereas carbon dioxide accounts for up to 60%.

The pattern of annual increase in methane concentration is of particular concern, with an annual percentage accumulation rate of 0.9%. Within the United Kingdom and Ireland, ruminant livestock are the primary source of methane production, accounting for approximately 20% of total methane production. This presents a considerable challenge for the dairy industry in the battle against global warming, and reduced methane emission is likely to be a major target for government policy within the next few years.

The UK has specific binding commitments relating to the reduction of greenhouse gas emissions, and all sectors of the economy are coming under increasing scrutiny in relation to their share in the overall emissions reduction target. To date, agriculture has been largely exempt from regulation, but the recently formed Committee on Climate Change is now specifically tasked with examining opportunities for cost effective mitigation relative to other sectors.

Ultimately these potentials may be translated into a greenhouse gas budget for agriculture. The scale of emissions and intensity of production systems in the dairy cattle sector, in comparison to other agricultural sectors, suggests that legislation to reduce methane emissions in the UK would have most impact on the UK dairy farming sector.

Improving the efficiency of energy use in dairy cows by reducing methane emission is critical for the future of the Northern Ireland dairy industry.

AFBI Hillsborough has undertaken a wide range of nutritional studies to investigate the effects of dietary, animal and management factors on methane emission from dairy cows for more than 10 years. The data collated from these studies have been used to develop a better understanding of factors influencing methane emission and to develop mitigation strategies to reduce methane emission under Northern Ireland conditions, while maintaining milk production and animal welfare.

One of the most effective approaches to reduce methane emission is to increase the level of individual animal performance. There is a negative relationship between milk yield and methane emission as a proportion of milk yield. For example, methane emission per kg milk yield (25.6 verses 30.6 litre per kg) could be reduced by 20% for a cow producing 8000 litre milk per lactation, in comparison with a cow producing 5500 litre milk per lactation (Table 1). Manipulation of forage and concentrate proportions in the total diet is another effective approach to reduce methane emission in dairy cows. Methane emissions from cows offered concentrate diets are lower than those given forage diets.

The third approach to reduce methane emission is to increase diet quality, such as dietary metabolisable energy concentration within normal nutritional strategies. The research at AFBI Hillsborough is also examining effects of different forage types (fresh grass vs. grass silage vs. maize silage vs. whole crop wheat silage) and use of dietary additives on methane emissions.

Accurate prediction of methane emissions from dairy cows is important in order to enable the Northern Ireland dairy farming industry to develop appropriate feeding and management regimes. These predictions will have a major role in the development of carbon footprint legislation for the Northern Ireland dairy industry.

Current research on reducing greenhouse gases (methane, carbon dioxide and nitrous oxide) at AFBI Hillsborough is examining the relationships between feed inputs and greenhouse gas outputs from different dairy farming systems. This modelling is based on whole farm systems, including determining greenhouse gas outputs from dairy cows, slurry, feed production, fertiliser and soil and associated emissions from fuel burning and electricity use.

Table 1.Effect of level of individual cow performance on methane emissions*
Parameter Low output system High output system
Live weight (kg) 550 650
Milk yield (kg per year) 5500 8000
Methane output (litre per year) 168,446 205,014
Methane output (litre per day) 461 562
Methane/milk yield (litre per kg) 30.6 25.6
*Total carbon footprint (carbon dioxide, methane and nitrous oxide) from different production systems needs to take account of emissions of these three greenhouse gases from other sources, e.g., replacement rate, manure and associated emission factors from feed production, fertiliser application, soil, fuel burning, electricity use, etc.

In December 2007, the AFBI Hillsborough Ruminant Nutrition team, in association with research groups from Teagasc and University College of Dublin, were successful in obtaining funding from the Department of Agriculture and Food (ROI) Stimulus Fund to evaluate effects of dietary changes on methane production from dairy cows. The aim of this project is to examine effects of different dairy production systems on methane emissions, and to identify feeding and management regimes which will reduce the environmental impact of dairy farming in Northern Ireland and the Republic of Ireland, whilst maintaining animal production and welfare. As part of this project, Dr. Camila Munoz has recently been appointed to the Ruminant Nutrition team at AFBI Hillsborough.

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