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

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 precise 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.

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.

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 the 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.