A Mathematical Modelling approach to defining factors which cause keel fractures in free range laying hens

Lead Research Organisation: University of Bristol
Department Name: Clinical Veterinary Science

Abstract

Skeletal health in laying hens is a major problem, reducing profitability, creating a poor public perception of egg production, and influencing consumer choice. Recent studies showed up to 80% of free range hens suffer keel bone breakage. Thus, despite many welfare benefits over battery cages, free range systems present unique and urgent economic and welfare problems. The 2012 EU ban on battery cage systems required that 18 million birds be "transferred" to alternative systems, mostly free range - equating to a potential 14 million more hens suffering bone breakage each year in the UK. The industry views this as unsustainable, and DEFRA regards this as a major welfare concern. Egg production in the UK is an important wealth creator, worth £868 million/year, but its narrow profit margins make it particularly vulnerable to market forces. The UK is entirely compliant with the 2012 battery cage ban, however this is not the case for most EU countries, and it is forecast that 23% of EU eggs will be produced illegally, with cheap imports a particular threat to the UK industry. Therefore resolution of these welfare and productivity problems is particularly timely, and falls within the BBSRC priority areas of Food Security, Animal Health, Welfare of Managed Animals, Data Driven Biology, Collaborative Research with Users, Systems Approaches to the Biosciences, Livestock Production and Research to Inform Public Policy.

Collisions within housing structures are believed to be the principle cause of keel fractures. However, difficulties in observing breaks as they happen prevent a clear understanding of the critical factors associated either with the hen or the particular impact which determines the occurrence or severity of a fracture. A lack of knowledge as to which factors are causal in keel fractures, prevents steps being taken to alleviate these in an informed and objective manner.

This study will replicate keel fractures in an ex-vivo impact testing system, allowing preise quantitation of bird factors such as weight, age, keel strength and compliance, and collision factors such as impact energy and material compliance, and directly relate these to the occurrence and severity of keel fractures. We will use a novel mathematical modelling approach that will define which factors influence fracture occurrence and provide a "risk assessment" of fractures in an individual bird or housed flock of given characteristics. The model will be validated using live birds placed in two contrary housing environments designed to provide low and high energy flights. Birds will be fitted with "impact loggers" (already correlated with the impact testing system) to determine the energies associated with arrested flights. Individual bird factors will be determined (as described above) at the end of the housing period, and keel breaks assessed. In this way the model predictions will be tested against actual fractures at individual bird and housing system level.

On-farm studies will determine kinetic energy profiles of particular commercial housing types which we have previously shown to have widely differing fracture rates. Our impact monitors will provide a physical measure of housing risk, and allow us to test the model in predicting fractures in commercial settings.

The outcomes from this study will allow commercial housing systems to be functionally assessed for their projected keel breakage risk, and will identify key elements of housing design or bird physiology that may be targeted by producers or policy makers to reduce fracture rates. Such a prospective "risk assessment" could be used to evaluate effects of housing changes within days rather than months. Therefore this study has the potential to greatly improve the health and welfare of laying hens, the public attitudes to egg production, and the profitability and sustainability of the UK egg industry in the face of difficulties arising from the EU ban on battery cage systems.

Technical Summary

Skeletal health in laying hens is a major welfare and economic problem, creating a poor public perception of egg production, and influencing consumer choice. Recent studies showed up to 80% of hens suffer keel bone breakage in free range systems (FRS). So, despite many welfare benefits, FRS present unique and urgent problems. Resolution of this problem is particularly timely, as the 2012 EU ban on battery cage systems requires that 18 million birds be "transferred" to alternative systems, mostly FRS - equating to a further 14 million hens suffering bone breakage each year in the UK. The industry views this as unsustainable, and DEFRA as a major concern. Collisions are believed to be the principle cause of keel fractures; however difficulties in observing breaks as they happen prevent a clear understanding of the critical factors.

This study will replicate keel fractures in an ex-vivo impact testing system. Bird factors, e.g. weight, age, keel strength and compliance, and collision factors such as impact energy and material compliance will be mathematically modelled to define which factors influence fracture occurrence and provide a "risk assessment" of fractures in a bird or flock of given characteristics. This model will be validated using live birds in housing environments designed to provide a range of bird and collision variables, and tested against predictions at individual bird and pen level. On-farm studies will determine kinetic energy profiles of particular commercial housing types with widely varying fracture rates to provide a physical measure of housing risk, and to test the model in predicting fractures in commercial settings.

The outcomes from this study will allow commercial housing systems to be functionally assessed for their keel breakage risk, and identify key elements of housing or bird physiology that may be modified by producers to reduce fracture rates, thus improving health and welfare, and the sustainability of the UK egg industry.

Planned Impact

Who will benefit, and how?

Laying Hens
The principal beneficiaries of this study are laying hens. Recent studies have shown that around 80% of free range hens suffer keel bone breakage at some stage in their laying cycle, representing approximately 8.5 million hens in the current UK flock. With the EU ban on conventional cages, up to 26.5 million hens will be housed in free range units, and the total number of laying hens with broken bones may rise to 23 million. Keel breaks lead to pain and prevent natural behaviours, and have been described by DEFRA (FAWC) as the most important problem facing laying hens. With our ongoing relationships with industry and policy makers we expect any benefits will be realised within or shortly beyond the timescale of the grant.

Egg producers
The UK industry produces 8.8billion eggs per year, with a retail value of £844million. With widely reported welfare problems, the producers are acutely aware of their poor public image. Also, reduced productivity, hen mortality and splintered bone in spent layer breast meat, represent a significant loss in profitability. UK producers regard the current breakage levels as a severe problem, and those projected post 2012 as unsustainable. The outcomes from this study will identify key elements of housing design or bird physiology that may be targeted by producers or policy makers to reduce fracture rates. The industry will benefit from improved productivity, and with the possibility of marketing eggs as "welfare friendly", enhanced profitability and public image, resulting in greater international competitiveness for UK producers.

Poultry house designers
The outcomes from this study will allow commercial housing systems to be functionally assessed for their projected keel breakage risk, and housing design to be modified by poultry house manufacturers to reduce fracture rates. Such a "risk assessment" could be used to evaluate effects of housing design changes within days rather than months, for he first time allowing objective optimisation for hen welfare.

Consumers
Public perception of egg production is poor, and consumer choice is increasingly driven by welfare issues. Eggs are an important component of our diet, and consumers will benefit from being provided "welfare friendly" eggs.

UK PLC
UK egg annual trade deficit is approximately £120 million. The UK is entirely compliant with the 2012 EU ban on battery cages, however as many as 17 EU states and 23% of production is expected to be non-compliant. The already narrow profit margins within UK industry will be squeezed further in competition with cheap non-compliant EU imports. Reducing or eliminating the economic burden associated with keel breakage in compliant free range systems, will protect and benefit both the egg industry and the UK economy.

Policy makers
Findings from our recent DEFRA and BBSRC studies are already guiding policy makers in the egg production industry. FAWC recently cited hen keel breakage as being of the highest priority. Policy makers will soon be seeking the sort of solutions to the unsustainably high bone breakage in free range hens that our research could provide. Andrew Joret, Research Director of Noble foods, our industrial partner, is Chairman of the British Egg Association, Deputy Chairman of the British Egg Industry Council (Chair of their Technical Committee), and Chairman of the International Egg Commission. He is ideally placed to influence these policy leaders. In addition, the British Egg Marketing Board Trust has offered to disseminate our findings (see letter of support).

Researchers
The training of technical and postdoctoral researchers will provide a skill resource which will translate into a number of research areas. Training is an essential part of this study, and researchers have access to a vast wealth of cross disciplinary expertise within the research team, and a rare opportunity to work with industry.

Publications

10 25 50
 
Description Although not yet complete, the findings of this study have shown that quantifiable hazards within housing systems are a major driver in the development of keel fractures in laying hens. We have shown that impact energies of a similar magnitude to those experienced in commercial housing systems are sufficient to generate fractures in an ex-vivo model, and that the energy of impact is related to the risk and severity of fractures.
As a result of this study a novel design of double-sensor 3D accelerometer has been developed able to distinguish defined behaviours which may be used in more comprehensive studies to remotely monitor behaviour in laying hens.
Accelerometer and video monitoring of hens in customised pens with a standard and low-impact design, have demonstrated differences in keel fracture rate and accelerometry readouts. Susceptibility to fracture has also been linked to mechanical and radiological outcomes from bones taken at dissection.
Exploitation Route The design of accelerometers has already been taken up by research groups in the US.
The accelerometers are also being used in a BBSRC funded iCASE studentship and will be used in a new BBSRC award (BB/N00860X).
The concepts are now being tested in collaboration with Vencomatic (NL) and Stonegate (UK) to determine how the data can be used to improve housing conditions to reduce keel fracture rates.
Sectors Agriculture, Food and Drink,Digital/Communication/Information Technologies (including Software),Electronics

URL http://www.bbsrc.ac.uk/news/food-security/2013/130312-pr-bone-fractures-in-laying-hens/
 
Description Although not yet complete, the findings of this study have shown that quantifiable hazards within housing systems are a major driver in the development of keel fractures in laying hens. We have shown that impact energies of a similar magnitude to those experienced in commercial housing systems are sufficient to generate fractures in an ex-vivo model, and that the energy of impact is related to the risk and severity of fractures. As a result of this study a novel design of double-sensor 3D accelerometer has been developed able to distinguish defined behaviours which may be used in more comprehensive studies to remotely monitor behaviour in laying hens. The two sensor 3D accelerometers developed in this study have been taken up by other research groups internationally, including Switzerland and the USA.
First Year Of Impact 2013
Sector Agriculture, Food and Drink,Electronics,Manufacturing, including Industrial Biotechology
Impact Types Societal,Economic

 
Description Assessing keel health in commercial laying hens and potential methods for improvement
Amount £43,000 (GBP)
Funding ID BB/K021303/1 
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 04/2013 
End 03/2016
 
Description Data-driven housing design to improve bone health and welfare in laying hens
Amount £82,600 (GBP)
Funding ID BB/L016842/1 
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 09/2014 
End 08/2018
 
Description Development of neural pain methodologies to improve assessment of bone-damage associated pain
Amount £2,500 (GBP)
Funding ID BB/K011316 
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 09/2012 
End 01/2013
 
Description Development, validation and refinement of protocols to improve the welfare of pullets and laying hens
Amount £32,100 (GBP)
Funding ID BB/N021959/1 
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 06/2016 
End 05/2019
 
Description Foundation for Food and Agricultural Research (US)
Amount $431,998 (USD)
Funding ID ID 550830 
Organisation Foundation for Food and Agriculture Research 
Start 03/2018 
End 02/2022
 
Description Functional housing systems for high welfare in laying hens: promoting natural behaviors in safe environments
Amount £540,500 (GBP)
Funding ID BB/N00860X/1 
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 07/2016 
End 06/2019
 
Description Functional housing systems for high welfare in laying hens: promoting natural behaviours in safe environments
Amount £540,600 (GBP)
Funding ID BB/N00860X/1 
Organisation Biotechnology and Biological Sciences Research Council (BBSRC) 
Sector Public
Country United Kingdom
Start 06/2016 
End 05/2019
 
Description GENESIS: Modular Insect Bioconversion System for On-site Animal Feed Production
Amount £572,566 (GBP)
Funding ID 104387 
Organisation Innovate UK 
Sector Public
Country United Kingdom
Start 11/2018 
End 09/2020
 
Description Identifying causes and solutions of keel bone damage in laying hens
Amount € 520 (EUR)
Funding ID CA15224 
Organisation European Cooperation in Science and Technology (COST) 
Sector Public
Country European Union (EU)
Start 02/2016 
End 01/2020
 
Description Increasing insect consumption by laying hens in free range systems to reduce feed costs, enhance food quality and improve welfare
Amount £20,000 (GBP)
Organisation The Soil Association 
Sector Learned Society
Country Unknown
Start 06/2015 
End 10/2015
 
Title Development of an ex vivo method for keel fracture generation and analysis 
Description A drop weight impact tester was used to generate precise quantifiable inpacts to the keels of (ex vivo) laying hens. This was used to estimate loads required for fracture, to determine the contribution of bird factors, such as bone mineral density, in determining fracture risk, and how change in housing materials might reduce fracture rates. 
Type Of Material Model of mechanisms or symptoms - non-mammalian in vivo 
Year Produced 2014 
Provided To Others? Yes  
Impact This method was used in studies funded by commercial collaborators to determine the influence of diet on fracture rates. 
 
Title Development of twin sensor triaxial accelerometer 
Description The tri-axial accelerometer has included an innovative hardware development of combining two sensors, one within the main body of the unit, and another on the end of a cable. This allows the specially designed firmware to exclude impact data from one sensor only, and only records data when both accelerometers register an event. Therefore trivial and irrelevant information, such as pecks to one of the sensors, to be excluded. Other firmware advances are an either/or threshold. 
Type Of Material Physiological assessment or outcome measure 
Year Produced 2015 
Provided To Others? Yes  
Impact The hardware and firmware innovations built into this technological development has allowed precise measurements of hen activity and exposure to hazards, whilst excluding irrelevant information. This has been utilised by groups in the US and Switzerland. 
 
Description Global Farm Platform 
Organisation Kerala Veterinary and Animal Science University
Country India 
Sector Academic/University 
PI Contribution Attended three international workshops. Obtained funding for research with KVASU, India Publication in Nature Organised an International conference with 180 delegates from over 30 countries
Collaborator Contribution Sethu Madhavan, KVASU; organised two workshops in Kerala, India in 2013 and 2015. Co-Applicant on BBSRC India Partnering Award. Graeme Martin, University of Western Australia; organised workshop in Perth Australia in 2014. Contributed to a co-authored Nature paper.
Impact Nature Paper. Steps to sustainable livestock International conference; Steps to sustainable livestock BBSRC India Partnering Award
Start Year 2013
 
Description Noble Foods 
Organisation Noble Foods Ltd
Country United Kingdom 
Sector Private 
PI Contribution Shared research findings
Collaborator Contribution Provided facilities essential for the collaboration. Provided hens for use in the study, and absorbed the costs of loss of productivity resulting from the research, such as loss of hens for sample collection.
Impact Publication, conference contributions, workshops.
Start Year 2012
 
Description Study of keel fractures in laying hens 
Organisation SDC Trailers
Country United Kingdom 
Sector Private 
PI Contribution Performing on-farm assessment of keel fractures Research activities relating to externally funded garnts
Collaborator Contribution Funding a study Providing access to farms Partner on a number of grant applications (two funded)
Impact Two successful grant applications (BBSRC and Soil Association)
Start Year 2013
 
Description Radio interview on Radio 4 "Farming Today" 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact The interview was part of a showcase of welfare related work undertaken at the University of Bristol School of Veterinary Science. I was describing our BBSRC funded work looking at the influence of ranging in influencing welfare measures in laying hens. I described the sensing technology we use to assess location and activity, as well as discussing enrichments designed to increase range use.
Year(s) Of Engagement Activity 2016