CIEL | Why Nitrogen Matters in Livestock Production 2023

Why Nitrogen Matters in Livestock Production Report

Nitrogen makes up the majority (78%) of the earth’s atmosphere and cycles in various forms between the atmosphere, plants, soils, water, animals, microbes and humans. Nitrogen (N) is an essential element in the production of proteins and DNA found in plants and animals. Nitrogen is largely lost from agriculture and food systems by either leaching from soils into watercourses as nitrate or as gaseous emissions. The key gas emissions containing nitrogen from agriculture are nitrous oxide, a greenhouse gas (GHG) and ammonia, an air pollutant.

Modern farming practices have increased reliance on artificial N fertiliser to increase crop yields, including feed and forage crops for livestock. However, the manufacture of artificial N fertilisers produces GHGs, and a proportion of the N is emitted to the atmosphere or lost through leaching or runoff after application.

This report aims to explore N cycling in livestock production systems, highlighting the roles of different forms of N, particularly its vital role in protein production, and where losses occur from the cycle. It will:

  • Describe the forms of N in livestock nutrition, and the importance of protein N in human and animal nutrition
  • Describe how N cycles through livestock production systems and where losses occur
  • Discuss current approaches to quantifying Nitrogen Use Efficiency (NUE)

CIEL has commissioned the new report ‘Why Nitrogen Matters in Livestock Production’ to inform the debate about NUE and its relevance to environmental stewardship and food security. As we seek to define and shift to a more sustainable food system, both nitrogen emissions and the value livestock add by providing superior protein food sources must be considered.

The report, published in September 2023, was accompanied by a special launch webinar on 12 September where we were joined by report authors Prof. John Newbold and Dr Gemma Miller from SRUC who presented key report findings and answered questions from the audience.

If you have a particular interest in future events and initiatives CIEL is planning around this topic area, please indicate this on the contact form and we’ll be in touch to discuss further.

Report now available – Why Nitrogen Matters in Livestock Production

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    CIEL recognises that a key part of its mission to facilitate the delivery of sustainable and circular food systems is to emphasise the critical value of nitrogen (N) in livestock production. By exploring how N cycles through the system, interacting with the atmosphere, soil, water, plants, animals and microbes, CIEL seeks to highlight the balance of N in livestock production and empower informed decision making to reduce N losses.

    Nitrogen is fundamentally important to the protein nutrition of all living organisms, and N fertilisers have been one of the cornerstones of modern agricultural productivity gains. However, the same intensification of modern agriculture that has brought about increases in productivity has also led to negative environmental impacts through excessive N losses from the system. In 2020, agriculture was responsible for 69% of the UK’s total nitrous oxide (N2O) emissions – a potent greenhouse gas (GHG) with 273 times the warming potential of carbon dioxide (CO2). Nitrogen also contributes to air pollution through ammonia (NH3) emissions and can pollute our waterways through nitrate (NO3-) leaching, underscoring its potential to influence negative changes in our natural environment.

    To reduce the environmental impact of N in livestock production, we first need a broader understanding of N’s interaction with the environment. This report takes a deep dive into the ‘nitrogen cycle’, explaining how agricultural practices shape the way N moves through this natural cycle and behaves in the atmosphere. Not only will this inform debate about how best to manage nitrogen use efficiency but also how N pollution could be mitigated. It is the whole cycle, and the roles N performs in its various forms, that needs to be understood if we are to integrate the understanding of this cycle into sustainable food systems of the future. Our goal should be to maximise value across nutritional quality (for animals and humans), environmental enhancement and resource use efficiency.

    CIEL is producing another relevant report focusing on the significance of protein quality. We recommend you read that as well, due to the fundamental link between N and protein in terms of nutritional quality and the efficiency of food production

    Nitrogen cycles through the atmosphere, soil, water, plants, animals and microbes; a natural cycle that underpins production of the food upon which we all depend. Nitrogen is an essential element for protein nutrition but is also present in a powerful GHG (nitrous oxide), an air pollutant (ammonia) and a water pollutant (nitrate). Nitrogen is continuously transformed between organic and inorganic forms through different biological processes. Nitrogen can have positive or negative impacts depending on its form and where it occurs. For example, protein is created by adding N to carbohydrate substrates but if not digested and absorbed by livestock it can lead to emissions from manures. Also, nitrate is an effective fertiliser, but can have negative effects when lost into watercourses. While plants and soil microbes transfer some N to the environment due to intrinsic inefficiencies, they can capture N from the environment and incorporate that into protein – something livestock cannot do. Livestock play a key role in the production of high-quality protein for human nutrition, such as meat, milk and eggs. No other proteins are so well suited to human nutrition in their natural form, and livestock can produce this from low-quality ‘feedstocks’.

    Ruminants are the only livestock species with the ability to gain protein from inorganic N in their diet through the symbiotic relationship they have with rumen microbes. Upgrading of nutritional value is why livestock were domesticated and why ruminants in particular play a key role in agriculture. During conversion of N in livestock feed to meat, milk and eggs, intrinsic inefficiencies lead to N being transferred to the environment through faeces and urine as nitrous oxide or ammonia. Nitrogen losses from livestock are also influenced by other factors including dietary N supply, production level, stage of growth, health and genetics.

    Animal manures should not be considered as waste as they can be used to improve soil health and fertility, replacing artificial N fertiliser to a varying extent. Appropriate management to reduce N losses from manure will increase the capacity to do this. Use of manures in this way reduces the carbon footprint costs associated with the production and application of artificial fertiliser. Nitrogen losses can be minimised with good management. Approaches to assessing nitrogen use efficiency (NUE) can be quantified at the farm level or as components of the farm system (e.g. animal or crop). It is recommended that NUE should be reported together with N surplus (as a proxy for N loss to the environment) and N output in products (as indicator of productivity).

    Inefficient use of N on farms is a result of both fundamental biological limits and attitudes to risk and genuine waste. One example is the use of ‘safety margins’ as an insurance policy when formulating diets or determining fertiliser application rates. Major N inefficiencies can be minimised through improved information and better decision support systems, by understanding the factors that influence N losses at different points, animal and plant productivity, and the need for N inputs. Economic considerations should be broadened to consider other dimensions of value from a sustainability context.
    To improve NUE in livestock farming we should:
    • Think in terms of nutrient circularity, with the N cycle being a key framing point
    • Use alternate feed options that minimise N losses without reducing N captured as protein in highly nutritious food products
    • Implement systems to capture and retain N, including those that can enhance growth of feed crops. Animal manures have an important role here
    • Use smart, data-led systems to quantify N resources, monitor changes over time and inform active management of N resources
    We have an urgent need for innovation in the following key areas in order to be able to manage N resources more effectively:
    • Measurement of N in key pools with sufficient accuracy – in soil, for example
    • Accurate assessment of changes in N pools (inputs, outputs, transfers between) to model these more effectively
    • Define a common scale of value for sustainable management of N resources that accounts for: nutritional value as protein, fertiliser value for plant productivity, potential value of N stores in the landscape and pollution impacts

    An understanding of the N cycle provides a better perspective of the role livestock play in agriculture. While increasingly subject to scrutiny in terms of their environmental impact, livestock offer enormous potential as an opportunity – or even a catalyst – to promote better environmental stewardship and sustainable agricultural practices while contributing to food security.

    Agriculture has been an integral part of the heritage of world cultures and communities through providing sustenance, economic prosperity and a cultural identity deeply rooted in the countryside. Against this backdrop, N cycling is a topic of fundamental importance, particularly in the context of livestock farming.
    Nitrogen, an essential element for all living organisms, plays a pivotal role in sustaining healthy ecosystems, both natural and agricultural. Livestock farming relies heavily on N inputs, primarily as fertilisers and animal feeds, to promote high productivity of feed crops and livestock. Nitrogen is also a unique element in nutrition being associated with protein but not carbohydrates or lipids. However, suboptimal management of N can lead to pollution and environmental degradation, negatively impacting ecosystems and human health, and contributing to climate change. We are becoming more aware of these negative impacts but need to look at them in the context of how N moves through the food system and also account for the value it adds.

    To address the challenges, a multifaceted approach is required, involving various stakeholders: government, policymakers and regulators; scientists, research institutions and innovators; fertiliser producers, animal feed manufacturers, farmers and, ultimately, consumers. Collaboration is needed to ensure our food systems make best use of resources but do not waste them. To raise awareness, support research and development of innovative solutions, and to implement best practice, we must have a holistic understanding of the food system. The N cycle underpinning the food system is a key concept to understand.

    This report outlines the important role N has in promoting crop growth and animal performance, together with the importance it has in transforming lower-quality feed components into high-quality protein. Livestock hold a unique position in this process through their ability to transform lower-quality feeds into very high-quality food products. Ruminants are uniquely capable of being able to harness the power of their rumen microbiome to ‘add’ protein to the equation while also breaking down complex carbohydrates (fibre) that cannot be digested by most other animal species. The N cycle is fundamental to this special process.

    So how can we improve the efficiency with which we use nitrogen, and avoid excessive losses from the food system?
    • Innovative feed options can be used to maximise the efficiency with which animals use protein which will reduce N content in animal waste and so play a significant role in increasing NUE within livestock systems
    • Adoption of technological solutions to hold or capture more N will be key strategies to improve efficiency in food production while minimising and capturing losses from the N cycle
    • Smart farming systems using sensor networks can
    help farmers manage N inputs through monitoring soil health, meeting crop N requirements and managing livestock manure appropriately. Data is key to delivering in this area
    • Artificial intelligence can use rich datasets to aid in predicting N demand and potential for losses
    across landscapes, allowing optimisation of fertiliser and manure applications, to maximise NUE
    • Embracing circular economy principles through integration of livestock farming with crop production can help close nutrient loops for N and other key nutrients, reducing need for synthetic inputs, simultaneously increasing nutrient use efficiency and reducing carbon footprint

    Several areas require innovations to enhance our ability to better manage N resources. These include:
    • Cheap and accurate methods for measuring N in the soil pool, by far the largest pool of N on most farms. This is critically important in modelling the N cycle since, as the largest pool, it acts as a buffer for plant production from a series of N inputs, including the capture of N from animal dung and urine
    • Robust and easy-to-use information systems for managing N resources that account for changes over relevant timescales and differential distribution of N in landscapes, to reduce need for additional inputs as safety margins for achieving performance goals:

    – For soils to help manage spatial application of organic and inorganic fertilisers

    – For body protein changes in lactating and growing animals at level of management groups or at individual animal level where nutritional control can be applied at that level

    • Simple, intuitive systems that allow us to equate different N pools or flows on a common scale of impact i.e. equating nutritional value of protein quality, to N value as a fertiliser, to pollution impacts of N2O (atmosphere) and NO3 – (water ways). This will help optimise N use models.

    Livestock are a key element of our food system for good reasons. They upcycle nutritional quality of feed to produce highly nutritious food and they play an important role in returning nutrients to soils through manures. This dual role is a key pillar for ‘regenerative agriculture’. This report shows where N can enter or leave the food system. Our aim should be to minimise unnecessary loss, through an understanding of the natural cycle and the use of innovative technologies to capture nutrients at risk of loss, together with monitoring N pools and flows between them on farm, to actively manage N resources. It is not a question of whether we need livestock. Rather it is how should we make best use of livestock.

    So, while livestock farming is increasingly subject to scrutiny in terms of its environmental impact, we must also shift perspective and recognise the potential of livestock farming as a catalyst or opportunity for promoting better environmental stewardship and sustainable agricultural practices. This will strengthen the resilience of the agricultural sector in the face of climate change and uncertainty,
    while continuing to play a vital role in providing society with essential nutrients in a highly-nutritious form. CIEL commends this report to the agri-food sector, government and wider public interested in farming and food, both here in the UK and abroad, to help inform debate about sustainable food systems.

    This fact sheet highlights the roles different forms of nitrogen have, explains where losses occur from the nitrogen cycle and how we can best measure efficient nitrogen use, and was informed by the key findings within the full report ‘Why Nitrogen Matters in Livestock Production’.

    Download the Factsheet here

    Download the full report

    If you would prefer not to download the report from our website, please get in touch using the form above and we will contact you back