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Livestock health and greenhouse gases: Ruminating on climate change

Livestock health and greenhouse gases: Ruminating on climate change

We are pleased that Philip Skuce, SEFARI Gateway and Moredun Research Institute and Michael MacLeodScotland’s Rural College are able to discuss how improving animal health can reduce the impact of livestock on climate change. This post was originally published by the Scottish Parliament’s Information Centre (SPICe), who commissioned SEFARI to write a series of blogs.

Climate change, both projected and realised, impacts on livestock production – and livestock impacts on climate change, both here in Scotland and globally. Changing weather patterns can affect livestock directly, in terms of heat and cold stress, availability of food and water, and dictates what can be raised where and when. Climatic change also affects the prevalence, seasonality and geographic spread of livestock diseases.

Less healthy livestock are inherently less efficient, and likely to have higher greenhouse gas (GHG) emission intensities, i.e. to produce more kg of GHG per kg of edible output. Improving animal health, therefore, provides a potential way of reducing emissions from Scottish livestock, thereby helping to achieve the target of reducing emissions by 90% by 2050 across the whole Scottish economy, as proposed by the Climate Change (Emissions Reduction Targets) (Scotland) Bill currently before Parliament. This blog discusses how improving animal health can reduce the impact of livestock on climate change.

 

Diseases

There have been recent concerns about incursions of ‘exotic’ diseases, such as Foot and Mouth Disease, Bluetongue and Schmallenberg, which can have a devastating impact on the livestock industry. However, arguably the most significant constraint on efficient and sustainable livestock production in the UK, now and in the short-to-medium term, comes from endemic diseases of livestock, i.e. diseases that are routinely present in many herds or flocks. These diseases can be caused by viral, bacterial and parasitic pathogens.

Some, if not all of these diseases, have life-stages in the wider environment, so their prevalence, seasonality and geographic spread can be affected by climatic conditions, farm management practices and land use decisions.

These diseases can affect single or multiple host species, several have carriers (known as vectors) like midges, ticks or intermediate hosts like mud snails, and sometimes are harboured in wildlife or the environment making them difficult, if not impossible, to eradicate.

They also vary in prevalence from farm-to-farm as well as within and between years. Endemic diseases can impact on the efficiency and productivity of livestock in many ways. They can cause a range of outcomes from sub-clinical disease, where the impact on productivity is difficult to diagnose, to clinical disease, where disease is visible, and mortalities may occur.

Some diseases have a short but significant impact during their acute phase, others become chronic with long-term impacts on production, fertility, feed conversion and animal welfare.

 

Vulnerability

Scottish livestock farms are particularly vulnerable to endemic disease impacts because they are largely pasture-based, and utilise unproductive rough grazing (land classed as Less Favoured Area, or Area under Natural Constraint). Ruminant livestock (e.g. sheep and cattle) are very good at producing human-edible protein i.e. converting something that can’t be eaten (grass and forage) into something that can (meat & dairy products). Monogastric livestock (e.g. pigs and poultry) are inherently more efficient than ruminants but Scotland’s Less Favoured Areas are not suitable for this type of livestock farming.

 

Scottish livestock farms are particularly vulnerable to endemic disease impacts because they are largely pasture-based, and utilise unproductive rough grazing.

 

Examples of losses due to disease include:

  • Fewer units of livestock product e.g. milk, meat or wool.
  • Animals taking longer to reach their target market weight.
  • Delayed onset and reduced quality of production e.g. for milk.
  • Lost production i.e. lambs or calves aborted due to infection.
  • Premature culling.
  • Waste of animal products condemned at slaughter.
  • Reduced reproductive performance.
  • Premature death of animals and animal welfare impacts.
  • Improving health

Agriculture and related land use is the second biggest source of emissions in the Scottish GHG inventory, with much of the emissions arising from ruminants (specifically beef cattle, dairy cattle and sheep) as a natural by-product of their digestive processes. The carbon footprint of ruminant meat and milk production is sensitive to changes in key parameters, such as maternal fertility rates, mortality rates, milk yield, growth rates and feed conversion ratios. These parameters are influenced by health, so improving health status would be expected to lead to reductions in carbon footprint.

 

Key studies

The impact of endemic disease is difficult to quantify, often relying on old data which do not reflect the natural occurrence of many of these diseases. A recent Defra-funded study attempted to quantify the impact of the top cattle health ‘conditions’ on the carbon footprint of beef and milk, and the reductions that could be made via veterinary and/or farm management. All cattle health conditions increased the GHG emissions per unit of milk or beef produced, with some conditions proving more tractable than others.

At the request of the Scottish Government, a rapid evidence assessment was undertaken of the potential contribution that could be made towards reducing the intensity of GHG emissions from Scottish animal agriculture by eradicating or controlling livestock diseases, focusing on the main livestock species, cattle and sheep.

In one of the very few observational studies on animal health impacts thus far, data from a 5-year field trial revealed that ineffective gastrointestinal nematode parasite control resulted in a 10% increase in GHG emissions compared to control groups. This was supported by data from direct measurements of GHG emissions from parasitized animals, which revealed a 10% increase in emissions from adult ewes and a 33% increase from lambs.

To combat exotic and endemic livestock disease in future, improved surveillance and access to novel diagnostic tests, vaccines and disease control strategies is needed. Also needed is a better understanding of disease presence and spread in response to climatic changes, including the generation of modelling and forecasting systems to provide early warning of disease outbreaks. Research to this end is ongoing within SEFARI, funded by the Scottish Government under its Strategic Research Programme 2016-2021.

 

Philip Skuce, Principal Scientist, Moredun Research Institute & SEFARI Knowledge Exchange Sector Lead for Livestock and Michael MacLeod, Climate Change Research Scientist, Scotland’s Rural College