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Commercial layer hen housing systems

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Ratification Date: 04 Nov 2021

Policy

  1. The housing system in any commercial egg production system must provide for both the health and the welfare of laying hens.
  2. The AVA supports the egg industry in their transition from conventional cages to alternative housing systems which better address both the health and welfare of laying hens.
  3. The AVA supports further research into housing systems that improve poultry health and welfare.
  4. Commercial egg producers should engage a veterinarian with poultry experience to develop comprehensive health, welfare, biosecurity, food safety and antimicrobial stewardship programs and monitor the effectiveness of these programs.

Purpose

To enable the AVA to publicly advocate for sustainable improvements to housing systems to improve the health and welfare of layer hens.

Background

Australian commercial egg farms vary in size from large, integrated businesses to small scale operations that may only produce a small number of eggs to supply a restricted or a local market.  It is important that regardless of the scale of the farming operation or the housing system, flock health and welfare are paramount.  Hens and the housing conditions should be closely monitored and assessed by egg producers in conjunction with veterinarians.

Eggs are currently produced in Australia by hens housed in cage, barn, aviary and free range systems.  Regardless of the housing system, all egg producers must meet the requirements outlined in state government animal welfare legislation and should also meet the minimum requirements outlined in the current edition of the Model Code of Practice for Domestic Poultry 4Th Edition.1  The intention is for this Code to be replaced by the Australian Animal Welfare Standards and Guidelines for Poultry with the Standards from this document to be incorporated into each state’s animal welfare legislation to achieve national consistency.

Hens in conventional cages are housed in a restricted environment and are unable to express the full range of natural behaviours.  This cannot be fully rectified with the continued use of caged housing systems.  Some countries, most notably those in Europe and more recently New Zealand, have legislated changes, including a phase-out or ban of conventional cage systems for laying hens.  These changes have led to the development and transition towards the use of alternative housing systems, including furnished or enriched cages, barn, free range and aviary systems. 

A transition towards alternative housing systems has also been gradually occurring in Australia over recent decades.  Given the known welfare issues with conventional cages, it is important that the egg industry continue to focus their research and efforts on ways to be able to achieve equivalent health, mortality rates, biosecurity, food safety and productivity outcomes for hens housed in alternative systems.  It is difficult to determine what level of compromise would be acceptable if equivalence in these areas cannot be achieved. 

A risk assessment approach or framework could be applied to enable a more objective comparison of welfare states across different housing systems.2   Such an approach would consider both the duration and severity of the welfare impact on the hen.  For hens housed in conventional cages, the welfare risks due to their inability to express natural behaviours are considered life-long for the whole population.  The welfare risks to hens in non-caged systems from behavioural issues, such as feather pecking and cannibalism, or disease when it occurs, may affect a lesser proportion of the flock but the impact on the individual hen may be greater, particularly if it leads to morbidity or mortality.  Flock management factors must also be a key consideration for ongoing research, as it is acknowledged that management and husbandry practices will be a greater determinant of welfare outcomes when hens are housed in alternative systems compared to conventional cages.

All housing systems for laying hens offer different advantages and disadvantages with respect to poultry welfare outcomes.

  1. Conventional cage systems:  Conventional cage housing systems do not allow laying hens the opportunity to exhibit some highly motivated natural behaviours.  Osteoporosis and Fatty Liver Haemorrhagic Syndrome may also occur more commonly when hens are housed in cages compared to other systems. 3,4  However, hens housed in conventional cage systems are recognised to have the lowest levels of infectious disease and mortality, including less cannibalism-related mortality, compared to non-caged systems.5,6  These systems also offer advantages associated with lower levels of internal and external parasites and improved foot health.3  Limited opportunities for faecal contamination of caged eggs can result in improved food safety outcomes.7  However, food safety outcomes can also depend on a range of other factors, including management factors, biosecurity and the Salmonella status of the flock.  Dependent on infrastructure and management, hens housed in cages may have the most reliable access to feed and water, due to small group size and cage design, improved thermal comfort and protection from predation and injury. 
  2. Furnished and colony cage systems:  The adoption of furnished cage and colony cage systems is limited in Australia at present but could increase in future, as has occurred overseas, particularly in Europe.  Furnished or colony cages may offer additional welfare benefits compared to conventional cages.  Providing for the hen’s behavioural needs, principally through the inclusion of a perch and in some cases, a scratch area and a nest box in the cage may increase opportunities for the expression of natural behaviours.  It is important that hens in furnished cages are provided with additional space to account for the space occupied by furnishings.  Sufficient resources should also be provided so as not to promote undue competition, which may be detrimental to hen welfare.  In one study, provision of more space was shown to increase expression of natural behaviours that indicate a positive welfare state and the birds in larger cages were shown to have increased tibial weight.8  The group size, particularly in colony systems or larger furnished cages, is also an important factor influencing welfare outcomes.  The normal social group of the chicken is 2-5 hens. Some furnished cages are designed for small groups, however most current designs for colony cage systems house up to 40-80 hens resulting in group mixing, competition for resources and social tension.  These larger group sizes may lead to increased risks of social hierarchy problems, such as feather-pecking and cannibalism.  The presence of perching in furnished cages may also elevate the risk of cloacal cannibalism3, especially when high numbers of chickens are housed together.  Use of smaller furnished cages designed for fewer birds may reduce these risks.
  3. Barn systems:  Barn housing systems provide increased opportunity for hens to exhibit natural behaviours in an indoor environment and this allows most of their behavioural needs to be met.  Social tension and competition for resources can still occur due to the large group size.  Barn systems provide nest boxes for laying and may or may not provide access to a litter or scratch area and perching.  Flock size is variable.  The advantages of barn systems include the provision of nest boxes and the opportunity for hens to dust-bathe if a scratch area is provided.  Aviary systems, which can be either barn or free range, are essentially multi-level indoor environments with perching, nests and other equipment able to be accessed across different levels of the system.  Feather pecking and mortality due to cannibalism, salpingitis and peritonitis are likely to be higher in barn systems than in conventional cage systems.6  There may also be increased risk of disease due to the opportunity for faecal-oral transmission of parasites and heightened ability for transmission of various infectious agents, including Erysipelothrix rhusiopathiae and the causative agents of Fowl Cholera and Spotty Liver Disease.3,9,10 Depending on the management and infrastructure, barn housing systems may also provide better thermal comfort than free range or outdoor systems, and also offer protection from predators.
  4. Free range systems:  Free range housing systems provide an opportunity for hens to venture outdoors, which may offer superior behavioural enrichment compared to other systems.  It is important that free range hens also have access to an indoor area to ensure their comfort and protection during adverse weather conditions and at night.  Free range flock size is variable.  Free range systems offer many of the other advantages of barn housing systems, including provision of nest boxes.  Disadvantages of free range systems include increased risks of negative interactions with wild birds and other animals, increased risk of injury and predation, reduced thermal comfort due to variable environmental conditions, and increased risk of infectious disease.  The risk of infectious disease may be a result of a number of factors, but can associated with poorer biosecurity, including exposure to wild birds, especially waterfowl, which can be a source of Avian Influenza.11   Increased faecal-oral transmission of a range of infectious agents, including parasites, can also occur in free range systems.  Disease transmission by other routes may also occur more readily.  Diseases such as Fowl Cholera, Spotty Liver Disease, salpingitis and peritonitis can similarly result in high mortality and production losses in free range systems.

The risk of faecal contamination of eggs is higher in both barn and free-range systems, compared with caged systems, particularly when eggs are laid outside of nest boxes.  This may have an impact on food safety.  However, food safety outcomes also depend on a range of other factors, including biosecurity and management. 

Poultry veterinarians play an integral role in ensuring optimal welfare outcomes across all types of layer hen housing systems.  They provide valuable advice about health and management and especially about disease prevention and biosecurity.  It is important that veterinarians have the tools available to help producers to minimise the impact of the various health and management challenges.  New and innovative solutions need to be considered because of the complex range of problems facing hens, producers and veterinarians in each type of system.  The goal should be research into the development of systems that maximise hen welfare, minimise biosecurity risk and allow ease of health monitoring of hens.

It is acknowledged that there are a number of other welfare issues associated with commercial egg production, including the euthanasia of male chicks, beak treatment and trimming and procedures for end-of-life flock depopulation.  These issues are equally complex and are to be reviewed independently, as this Policy only relates to laying hen housing systems.

Other relevant policies and position statements

Beak trimming of commercial poultry

References

  1. Model Code of Practice for the Welfare of Animals – Domestic Poultry, 4th Edition, prepared for the Primary Industries Standing Committee, published by CSIRO, 2002, SCARM Report No. 83.
  2. Paton MW, Martin PAJ & Fisher AD. 2013. ‘Risk assessment principles in evaluation of animal welfare’, Animal Welfare 22: 277-285.
  3. Lay DC, Fulton RM, Hester PY, Karcher DM, Kjaer JB, Mench JA, Mullens BA, Newberry RC, Nicol CJ, O’Sullivan NP & Porter RE. 2011. ‘Hen welfare in different housing systems’, Poultry Science, 90(1), 278-294.
  4. Shini S. & Bryden WL. 2009. ‘Occurrence and control of Fatty Liver Haemorrhagic Syndrome (FLHS) in caged hens. A report for the Australian Egg Corporation Limited. AECL Publication No UQ-105A.
  5. Elson HA & Croxall RA. 2006. ‘European study on the comparative welfare of laying hens in cage and non-cage systems’, Archiv für Geflügelkunde, 70(5), 194–198.
  6. Fossum O, Jansson, DS, Etterlin, PE & Vagsholm, I. 2009. ‘Causes of mortality in laying hens in different housing systems in 2001 to 2004’, Acta Vet Scand, Jan 15, 51-3.
  7. Jones DR, Anderson KE & Musgrove, MT. 2011. ‘Comparison of environmental and egg microbiology associated with conventional and free-range laying hen management’, Poultry Science, 90(9), 2063-8
  8. Meng F, Chen D, Li X, Li J & Bao J. 2017. ‘The effect of large or small furnished cages on behaviours and tibia bone of laying hens’, Journal of Veterinary Behaviour, 17, 69-73.
  9. Nicol CJ, Bouwsema, J, Caplen, G, Davies, AC, Hockenhull, J, Lambton, SL, Lines, JA, Mullan, S & Weeks, CA. 2017. ‘Farmed Bird Welfare Science Review’.  A report for the Victorian Department of Economic Development, Jobs, Transport and Resources (DEDJTR). ISBN 978-1-925629-82-2.
  10. Courtice JM, Mahdi LK, Groves PJ & Kotiw M. 2018. ‘Spotty Liver Disease: A review of an ongoing challenge in commercial free-range egg production’, Veterinary Microbiology, 227, 112-118.
  11. Singh M, Toribio J-A, Scott AB, Groves P, Barnes B, Glass K, Moloney B, Black A & Hernandez-Jover M. 2018. ‘Assessing the probability of introduction and spread of avian influenza (AI) virus in commercial Australian poultry operations using an expert opinion elicitation’, PLoS One. 13(3)

Date of ratification by AVA Board 5 November 2021