Why do hens smother? An investigation into the causes and consequences of smothering
Lead Research Organisation:
Newcastle University
Department Name: Sch of Natural & Environmental Sciences
Abstract
There can be no egg farmer who wants to walk into a chicken house and find a pile of dead birds, only to know the same event could happen again tomorrow and the next day, without being able to prevent it. This is the impact of smothering, a strange behaviour whereby hens pile on top of each other causing deaths of chickens at the bottom of the pile. No-one really understands why chickens do this and often they appear to move slowly and calmly in the lead up to smothering. Naturally, farmers who produce eggs would like to reduce this behaviour, but it doesn't happen when they are present in the farm watching the birds. It happens intermittently and is hard to predict. New approaches are therefore urgently needed to understand this behaviour. The behaviour and motivations of birds during these smothering events is of great interest to scientists because animals don't often cause the death of other animals of the same species in such an apparently calm manner. This research aims to investigate when, where and how smothering happens, and the effect smothering has on the chickens that survive. The fact that smothering is unpredictable means that a large number of farms are needed in order to study this behaviour. Working with an egg producing company we will have access to 110 flocks of birds. These all have a monitoring system, Birdbox, which records information about the environment of the hens (e.g. ventilation and temperature), food and water intake, egg production, and numbers and causes of hen deaths. We will also gather further information on whether these chickens were stressed when they were still chicks, details of the barns where they live, at what time smothering events occur and where in the barn they happen. All this information will be used find the potential causes of smothering and to see if there could be early warning signs before it happens. Whilst useful for understanding the development of smothering behaviour, these analyses by themselves won't identify the immediate cues that cause chickens to move in ways which smother others, or indeed what movements cause smothering. To address this we will place heart rate monitors on chickens and film smothering events using thermal and standard cameras. The thermal cameras will allow us to automatically measure movements of chickens to be able to create a realistic simulation of smothering. The simulation of smothering will allow us to understand what it is about hen's movements which means other hens don't move out the way and end up getting killed. Heart rate monitors will enable us to see whether stress might trigger smothering, or whether birds really are as calm as they appear when starting to smother one another. We will also measure other indications of a stressed flock and hen welfare: fearfulness toward humans and novel objects, stress hormones in the egg, faults in eggshells and bone injuries. It is important to understand smothering behaviour because it harms chickens welfare and causes deaths of 1.4% of birds in a flock die from smothering (this equates to 21% of all mortalities) and can kill more than 20% of hens in badly affected flocks. Whilst 1.4% overall may sound small, this equates to over 300,000 hens deaths and 86 million eggs lost across the UK egg farms. The real impact of smothering is probably much greater than this because often hens killed by smothering will not be recognised as such. In addition, the potential for injuries and stress in those that survive have never before been investigated. Our results will be used to understand what causes this behaviour which will help farmers know how to intervene to prevent smothering. Our results will be able to reveal if information in the BirdBox could provide a warning that smothering is imminent, or whether particular movements made by hens might be useful for early warnings of smothering. Through this project we will benefit by understanding the true impact of smothering for laying hen welfare.
Technical Summary
We will undertake the first comprehensive study of smothering in this industry partnered LINK grant. Smothering is an aberrant collective behaviour which causes 21% of mortality in laying hens through piling of birds on top of one another in a concentrated area. We focus on risk factors and mechanisms involved in 'creeping smothers', which occur in open spaces, with slow bird movement and in the absence of any obvious trigger. In an exceptional opportunity, this project will have access to 110 flocks of laying hens equipped with systems to automatically collect real-time data on environmental, resource use and productivity parameters. Additional data will be collected on early life stress and stressors. This data will be used for an epidemiological analysis of risk factors for smothering events (using marginal structure models to estimate historical and current influences). The mechanisms of smothering will be studied using two approaches: simulations of smothering using agent based models; and measuring behaviour and physiology of birds before, during and after smothering events. Flocks which show high levels of smothering will be filmed using thermal cameras, to track chicken movements during smothering events. Trajectories of movements from individual birds will be used to build and test simulations. Chickens in high smothering flocks will also be fitted with heart rate monitors, and after a smothering event, egg albumen corticosterone levels, novel object tests, egg shell irregularities, and keel bone injuries will be measured and compared to age-matched, low smothering flocks. These parallel approaches will reveal local cues of bird movement which result in smothering, the arousal state of birds performing the behaviour, and the welfare consequences of smothering for hens that survive. The project will offer practical and theoretical insights into this welfare concern which costs the UK poultry industry more than £6.5million/yr and 86 million eggs.
Planned Impact
The main benefits of this project are, understanding: 1) the causes smothering, 2) the potential for early warnings of smothering, 3) the cost and welfare impact of smothering. The project supports future use of sensors (image, thermal and wearables) and sensor management systems for livestock. Key beneficiaries are: non-cage egg producers, retailers, assurance schemes & policy makers, the public, and livestock monitoring & technology companies. There will be considerable benefits to hen welfare.
UK non-cage egg producers (3242 farms/24million hens, ~60% of the market) are the primary beneficiaries of this research. For badly affected flocks in non-cage housing, smothering can result in mortality of over 20%; on average it costs more than £3535/flock annually or £6.5 million across the UK. We will identify risk factors of smothering, so producers can implement changes to reduce occurrence. We will provide knowledge of the causes of smothering which is needed to design appropriate interventions, as current methods are ineffective. It is likely that deaths by smothering and other impacts are vastly underestimated. This project will provide producers with information on welfare and cost impacts of smothering to empower them to devote resources accordingly. Smothering also has an emotional impact on many producers when they find a pile of dead hens knowing they are unable to predict or effectively control the problem. We will identify potential methods for predicting outbreaks of smothering, using environmental variables in BirdBox and hen movement patterns which could be automatically detected. UK farmers are under pressure to improve animal welfare, sustainability and environmental impacts, whilst turning a healthy profit. Reducing smothering increases profits and improves animal welfare. Hen health and use of antimicrobials would be improved by reducing stress or injuries caused by smothering. Lower hen mortality and stress would result in more sustainable production. Global trends predict a 45% increase in a global non-cage egg industry worth $6559 million by 2025. Smothering will be a new problem for producers changing from cage to non-cage systems. Therefore secondary beneficiaries for this project will be new egg producers globally.
Retailers will benefit from the project by enhancing their reputation for retailing high welfare products, through sales of eggs from farms where smothering had been reduced. Key retailers, M&S and McDonalds, support this project through dissemination activities.
Assurance scheme providers and Policy makers will benefit from the research by incorporating information on smothering and mitigation strategies into their welfare assessment protocols or certification standards for laying hens. RSPCA Assurance, Soil Association, and Lion code Defra and Animal Health and European Food Standards Agency, EFSA are the key organisations which stand to benefit.
Animal welfare organisations such as the RSPCA, Compassion in World Farming, and the Laying Hen Welfare Forum (LHWF) will benefit from additional information on smothering to help them protect the welfare of hens.
The Public has displayed high consumer demand for high welfare eggs yet smothering occurs more in high welfare systems. Information on smothering is not generally available to the public and this project will help raise awareness.
Livestock monitoring and technology companies will benefit from this research in two ways. Firstly through demonstration of the value of monitoring systems for understanding association with health and welfare concerns. Use of the monitoring system for epidemiology research in this project will support utilisation and uptake of these systems in the future. Secondly, through value demonstration and development, this project will support future Precision Livestock Farming application of animal tracking, wearables for monitoring sentinel animals, and acoustic monitoring.
UK non-cage egg producers (3242 farms/24million hens, ~60% of the market) are the primary beneficiaries of this research. For badly affected flocks in non-cage housing, smothering can result in mortality of over 20%; on average it costs more than £3535/flock annually or £6.5 million across the UK. We will identify risk factors of smothering, so producers can implement changes to reduce occurrence. We will provide knowledge of the causes of smothering which is needed to design appropriate interventions, as current methods are ineffective. It is likely that deaths by smothering and other impacts are vastly underestimated. This project will provide producers with information on welfare and cost impacts of smothering to empower them to devote resources accordingly. Smothering also has an emotional impact on many producers when they find a pile of dead hens knowing they are unable to predict or effectively control the problem. We will identify potential methods for predicting outbreaks of smothering, using environmental variables in BirdBox and hen movement patterns which could be automatically detected. UK farmers are under pressure to improve animal welfare, sustainability and environmental impacts, whilst turning a healthy profit. Reducing smothering increases profits and improves animal welfare. Hen health and use of antimicrobials would be improved by reducing stress or injuries caused by smothering. Lower hen mortality and stress would result in more sustainable production. Global trends predict a 45% increase in a global non-cage egg industry worth $6559 million by 2025. Smothering will be a new problem for producers changing from cage to non-cage systems. Therefore secondary beneficiaries for this project will be new egg producers globally.
Retailers will benefit from the project by enhancing their reputation for retailing high welfare products, through sales of eggs from farms where smothering had been reduced. Key retailers, M&S and McDonalds, support this project through dissemination activities.
Assurance scheme providers and Policy makers will benefit from the research by incorporating information on smothering and mitigation strategies into their welfare assessment protocols or certification standards for laying hens. RSPCA Assurance, Soil Association, and Lion code Defra and Animal Health and European Food Standards Agency, EFSA are the key organisations which stand to benefit.
Animal welfare organisations such as the RSPCA, Compassion in World Farming, and the Laying Hen Welfare Forum (LHWF) will benefit from additional information on smothering to help them protect the welfare of hens.
The Public has displayed high consumer demand for high welfare eggs yet smothering occurs more in high welfare systems. Information on smothering is not generally available to the public and this project will help raise awareness.
Livestock monitoring and technology companies will benefit from this research in two ways. Firstly through demonstration of the value of monitoring systems for understanding association with health and welfare concerns. Use of the monitoring system for epidemiology research in this project will support utilisation and uptake of these systems in the future. Secondly, through value demonstration and development, this project will support future Precision Livestock Farming application of animal tracking, wearables for monitoring sentinel animals, and acoustic monitoring.
Organisations
Publications
Armstrong D
(2023)
The effect of piling behavior on the production and mortality of free-range laying hens
in Poultry Science
Collins L.M.
(2010)
Welfare epidemiology as a tool to assess the welfare impact of inherited defects on the pedigree dog population
in Animal Welfare
Gray H
(2020)
Why Do Hens Pile? Hypothesizing the Causes and Consequences.
in Frontiers in veterinary science
Herbert G.
(2021)
Extreme crowding in laying hens during a recurrent smothering outbreak
in Veterinary Record
Herbert GT
(2021)
Extreme crowding in laying hens during a recurrent smothering outbreak.
in The Veterinary record
Ogbonna A
(2023)
Effect of dietary vitamin D3 and ultraviolet-B light on the behaviour and growth of broilers challenged with social isolation stress
in Applied Animal Behaviour Science
Ogbonna A
(2022)
Effect of Dietary Vitamin D3 and Ultraviolet B Light on Growth Performance, Blood Serum Parameters, Gut Histology, and Welfare Indicators of Broilers
in Frontiers in Animal Science
Van Der Sluis M
(2022)
Early locomotor activity in broilers and the relationship with body weight gain.
in Poultry science
Description | We have conducted a review of scientific literature to identify the potential impacts of smothering and piling behaviour in laying hens which we will test. We have been working on a new way to measure stress in laying hens using subtle differences in the surface of the eggs. Once we are able to confirm this is a good measure of stress in hens we will use this to compare stress in flocks that perform piling behaviour and those that do not. |
Exploitation Route | Other academics have been using the review to develop their own research projects on piling and smothering in different countries. We have pilot data to suggest eggs can be used as a non-invasive measure of stress and plan to present this at conferences in summer 2022. We have been working with FAI who are industry partners on this award to incorporate sound analysis into their chicken management system (The BirdBox) using data collected on vocalisations during this project. |
Sectors | Agriculture Food and Drink Digital/Communication/Information Technologies (including Software) |
Description | Our research on smothering has supported the use of monitoring welfare using sound analysis so that vocalisations can be monitored. As a result FAI farms (an industrial partner on the project) has incorporated microphones into their laying hen management system, the BirdBox. The Birdbox has additional functionality developed as a result of the project including alert systems and the facility to download data. A new KTP has commenced related to monitoring welfare using sensor technology (sound, thermal imaging, imaging) |
First Year Of Impact | 2022 |
Sector | Agriculture, Food and Drink,Digital/Communication/Information Technologies (including Software) |
Impact Types | Societal Economic |
Description | 1885 - AKT, Newcastle University & FAI Farms Limited |
Amount | £31,664 (GBP) |
Organisation | Innovate UK |
Sector | Public |
Country | United Kingdom |
Start | 03/2024 |
End | 07/2024 |
Description | Public description The application of animal welfare science theory to key environmental, welfare and industry KPI's to develop a novel diagnostic and prediction service for non-invasive bio surveillance. Providing a decision support tool to support adopt |
Amount | £146,091 (GBP) |
Funding ID | KTP 13265 |
Organisation | Newcastle University |
Sector | Academic/University |
Country | United Kingdom |
Start | 03/2023 |
End | 09/2025 |
Title | Birdbox Chicken management system adding sound analysis |
Description | Sound analysis has been added to the birdbox system as an additional tool to measure welfare. This is the first animal based measure to be included in the laying hen management system. https://www.faifarms.com/birdbox/ |
Type Of Technology | New/Improved Technique/Technology |
Year Produced | 2021 |
Impact | Only at testing stage so not notable impacts yet. |
URL | https://www.faifarms.com/birdbox/ |
Description | BBC radio 4 Farming Today |
Form Of Engagement Activity | A broadcast e.g. TV/radio/film/podcast (other than news/press) |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Public/other audiences |
Results and Impact | Interview on vocalisations as an indicator of chick welfare following a publication of a paper on the topic. The interview appeared on BBC Radio 4s Farming Today. |
Year(s) Of Engagement Activity | 2021 |
Description | Compassion in World farming lunch time research series |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Third sector organisations |
Results and Impact | Presentation to Compassion in World Farming staff about why hens smother resulting on increased focus and awareness of this welfare organisation. |
Year(s) Of Engagement Activity | 2021 |
Description | International Joint Webinar: Recent Advances in Poultry Welfare on 27th January 2021 |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Postgraduate students |
Results and Impact | Two talks presented on the work carried out on the project and on the future work we plan to conduct. Almost 100 delegates from the UK and Malaysia attended which disseminated our work internationally. We plan to hold another symposium in the future where we can share updates. |
Year(s) Of Engagement Activity | 2021 |
Description | Invited talk at Linkoping University on Behaviour Informatics for Animal Welfare |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Postgraduate students |
Results and Impact | Presentation to famous Ethology and Welfare group at Linkoping Univeristy Sweden |
Year(s) Of Engagement Activity | 2020 |
Description | Invited talk at Teramo University |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Postgraduate students |
Results and Impact | I was invited to present a lecture for a Masters program at Teramo University, Italy. I spoke about the project and intended outcomes. This lecture disseminated our work at a international level. |
Year(s) Of Engagement Activity | 2020 |
Description | Key note talk at The European Federation for Animal Science |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Professional Practitioners |
Results and Impact | A keynote talk at 72nd EAAP conference for Animal Science attended by many industry experts |
Year(s) Of Engagement Activity | 2021 |
Description | Letters to a pre-scientist |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Schools |
Results and Impact | I write to a middle school-aged student in Chicago via the organisation Letters to a Pre-Scientist. I tell them about my work and they ask questions about what it's like to be in STEM. |
Year(s) Of Engagement Activity | 2020,2021 |
URL | https://www.prescientist.org/ |
Description | National Farmers Union Research Seminar |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Industry/Business |
Results and Impact | A presentation to the National Farmers Union on poultry research which resulted in lots of questions and approaches for collaborations/ study participation. |
Year(s) Of Engagement Activity | 2021 |
Description | Presentation at international conference on applied animal behaviour |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Postgraduate students |
Results and Impact | Presentation at the International Society for Applied Ethology. Lots of questions and follow up conversations. |
Year(s) Of Engagement Activity | 2022 |
Description | Skype a scientist |
Form Of Engagement Activity | Participation in an activity, workshop or similar |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Schools |
Results and Impact | Skype event arranged via Skype a Scientist organisation. Spoke with pupils about being an animal welfare researcher and about the current BBSRC project. The teacher's feedback was that the pupils reported interest in science and animals after the event and found benefit of having heard from a real scientist about their work. |
Year(s) Of Engagement Activity | 2020 |
Description | Talk at Industry and postgraduate research event in Switzerland for European Training Network |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Postgraduate students |
Results and Impact | A talk to the European Training Network Chicken Stress on working with industry given jointly by Professor Asher (PI) & Mr Brass (Lakes Eggs). In attendance were approximately 30 postgraduate researchers and their supervisors and key members of the poultry industry from across Europe. |
Year(s) Of Engagement Activity | 2021 |
Description | Talk at Upsala University |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | International |
Primary Audience | Postgraduate students |
Results and Impact | Talk at Upsala University |
Year(s) Of Engagement Activity | 2024 |