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Food, fibre and pharmaceuticals from animals
REVIEW

Cage production and laying hen welfare

Paul H. Hemsworth https://orcid.org/0000-0002-0211-0751
+ Author Affiliations
- Author Affiliations

Animal Welfare Science Centre, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville, Vic. 3010, Australia. Email: phh@unimelb.edu.au

Animal Production Science 61(10) 821-836 https://doi.org/10.1071/AN19609
Submitted: 4 November 2019  Accepted: 25 February 2020   Published: 5 February 2021

Abstract

Although many factors affect the welfare of hens housed in cage and non-cage systems, welfare issues in cage systems often involve behavioural restrictions, whereas many welfare issues in non-cage systems involve health and hygiene. This review considers and compares the welfare of laying hens in cages, both conventional and furnished cages, with that of hens in non-cage systems, so as to highlight the welfare implications, both positive and negative, of cage housing. Comparisons of housing systems, particularly in commercial settings, are complex because of potentially confounding differences in physical, climatic and social environments, genetics, nutrition and management. Furthermore, some of the confounding factors are inherent to some specific housing systems. Nevertheless, research in commercial and experimental settings has indicated that hens in conventional and furnished cages have lower (or similar), but not higher, levels of stress on the basis of glucocorticoid concentrations than do hens in non-cage systems. Furthermore, caged hens, generally, have lower mortality rates than do hens in non-cage systems. However, the behavioural repertoire of laying hens housed in conventional cages is clearly more compromised than that of hens in non-cage systems. In contrast to conventional cages, furnished cages may provide opportunities for positive emotional experiences arising from perching, dust-bathing, foraging and nesting in a nest box. Some have suggested that the problems with modern animal production is not that the animals are unable to perform certain behavioural opportunities, but that they are unable to fill the extra time available with limited behaviours when they have no need to find food, water or shelter. Environmental enrichment in which objects or situations are presented that act successfully, and with a foreseeable rewarding outcome for hens by also providing regular positive emotional experience, is likely to enhance hen welfare. Research on cage systems highlights the importance of the design of the housing system rather than just the housing system per se.

Keywords: animal behaviour, animal welfare, housing, management, poultry, stress physiology.


References

Abrahamsson P, Tauson R (1997) Effects of group size on performance, health and birds’ use of facilities in furnished cages for laying hens. Acta Agriculturæ Scandinavica. Section A. Animal Science 47, 254–260.
Effects of group size on performance, health and birds’ use of facilities in furnished cages for laying hens.Crossref | GoogleScholarGoogle Scholar |

Adams AW, Craig JV (1985) Effect of crowding and cage shape on productivity and profitability of caged layers: a survey. Poultry Science 64, 238–242.
Effect of crowding and cage shape on productivity and profitability of caged layers: a survey.Crossref | GoogleScholarGoogle Scholar |

Aerni V, El-Lethey H, Wechsler B (2000) Effect of foraging material and food form on feather pecking in laying hens. British Poultry Science 41, 16–21.
Effect of foraging material and food form on feather pecking in laying hens.Crossref | GoogleScholarGoogle Scholar | 10821517PubMed |

Al-Rawi B, Craig JV (1975) Agonistic behavior of caged chickens related to group size and area per bird. Applied Animal Ethology 2, 69–80.
Agonistic behavior of caged chickens related to group size and area per bird.Crossref | GoogleScholarGoogle Scholar |

Al-Rawi B, Craig JV, Adams AW (1976) Agonistic behavior and egg production of caged layers: genetic strain and group-size effects. Poultry Science 55, 796–807.
Agonistic behavior and egg production of caged layers: genetic strain and group-size effects.Crossref | GoogleScholarGoogle Scholar |

Alm M, Tauson R, Holm L, Wichman A, Kalliokoski O, Wall H (2016) Welfare indicators in laying hens in relation to nest exclusion. Poultry Science 95, 1238–1247.
Welfare indicators in laying hens in relation to nest exclusion.Crossref | GoogleScholarGoogle Scholar | 26994207PubMed |

Appleby MC (2003) The European Union ban on conventional cages for laying hens: history and prospects. Journal of Applied Animal Welfare Science 6, 103–121.
The European Union ban on conventional cages for laying hens: history and prospects.Crossref | GoogleScholarGoogle Scholar | 12909526PubMed |

Appleby MC, Smith SF, Hughes BO (1992) Individual perching behaviour of laying hens and its effects in cages. British Poultry Science 33, 227–238.
Individual perching behaviour of laying hens and its effects in cages.Crossref | GoogleScholarGoogle Scholar | 1623413PubMed |

Appleby MC, Walker AW, Nicol CJ, Lindberg AC, Freire R, Hughes BO, Elson HA (2002) Development of furnished cages for laying hens. British Poultry Science 43, 489–500.
Development of furnished cages for laying hens.Crossref | GoogleScholarGoogle Scholar | 12365505PubMed |

Appleby MC, Mench JA, Hughes BO (2004) ‘Poultry behaviour and welfare.’ (CABI Publishing: Wallingford, UK)

Archer GS, Moreira M, Farnell MB (2017) Evaluation of fear and stress in white layers housed in either conventional cages or enriched colony cage. International Journal of Poultry Science 16, 467–474.
Evaluation of fear and stress in white layers housed in either conventional cages or enriched colony cage.Crossref | GoogleScholarGoogle Scholar |

Barnett JL, Hemsworth PH, Cronin GM, Jongman EC, Hutson G (2001) A review of the welfare issues for sows and piglets in relation to housing. Australian Journal of Agricultural Research 52, 1–28.
A review of the welfare issues for sows and piglets in relation to housing.Crossref | GoogleScholarGoogle Scholar |

Barnett JL, Tauson R, Downing JA, Janardhana V, Lowenthal JW, Butler KL, Cronin GM (2009) The effects of a perch, dust bath, and nest box, either alone or in combination as used in furnished cages, on the welfare of laying hens. Poultry Science 88, 456–470.
The effects of a perch, dust bath, and nest box, either alone or in combination as used in furnished cages, on the welfare of laying hens.Crossref | GoogleScholarGoogle Scholar | 19211513PubMed |

Bessei A, Kjaer JB (2015) Feather pecking in layers–state of research and implications. In ‘Proceedings of the 26th annual Australian poultry science symposium’, 9–11 February 2015, Sydney, NSW, Australia. pp. 214–221. (University of Sydney: Sydney, NSW, Australia)

Bestman M, Koene P, Wagenaar J-P (2009) Influence of farm factors on the occurrence of feather pecking in organic reared hens and their predictability for feather pecking in the laying period. Applied Animal Behaviour Science 121, 120–125.
Influence of farm factors on the occurrence of feather pecking in organic reared hens and their predictability for feather pecking in the laying period.Crossref | GoogleScholarGoogle Scholar |

Black H, Christensen N (2009) ‘Comparative assessment of layer hen welfare in New Zealand.’ (MAF Biosecurity New Zealand: Wellington, New Zealand)

Blatchford RA, Fulton RM, Mench JA (2016) The utilization of the Welfare Quality® assessment for determining laying hen condition across three housing systems. Poultry Science 95, 154–163.
The utilization of the Welfare Quality® assessment for determining laying hen condition across three housing systems.Crossref | GoogleScholarGoogle Scholar | 26240396PubMed |

Boissy A, Manteuffel G, Jensen MB, Moe RO, Spruijt B, Keeling LJ, Winckler C, Forkman B, Dimitrov I, Langbein J (2007) Assessment of positive emotions in animals to improve their welfare. Physiology & Behavior 92, 375–397.
Assessment of positive emotions in animals to improve their welfare.Crossref | GoogleScholarGoogle Scholar |

Broom DM (1986) Indicators of poor welfare. The British Veterinary Journal 142, 524–526.
Indicators of poor welfare.Crossref | GoogleScholarGoogle Scholar | 3594185PubMed |

Broom DM (2001) Coping, stress and welfare. In ‘Coping with challenge: welfare in animals including humans’. (Ed. DM Broom) pp. 1–9. (Dahlem University Press: Berlin, Germany)

Broom DM, Corke MJ (2002) Effects of disease on farm animal welfare. Acta Veterinaria Brno 71, 133–136.
Effects of disease on farm animal welfare.Crossref | GoogleScholarGoogle Scholar |

Broom DM, Fraser AF (2015) ‘Domestic animal behaviour and welfare.’ (CABI: Wallingford, UK)

Buil T, Chacon G, Maria G, Cepero R (2006) The effects of cage model, genotype and rearing treatment upon faecal corticosterone. LayWel Deliverable 5.4. In ‘Welfare implications of changes in production systems for laying hens’.

Campbell DLM, Makagon MM, Swanson JC, Siegford JM (2016) Litter use by laying hens in a commercial aviary: dust bathing and piling. Poultry Science 95, 164–175.
Litter use by laying hens in a commercial aviary: dust bathing and piling.Crossref | GoogleScholarGoogle Scholar |

Cloutier S, Newberry RC, Honda K, Alldredge JR (2002) Cannibalistic behaviour spread by social learning. Animal Behaviour 63, 1153–1162.
Cannibalistic behaviour spread by social learning.Crossref | GoogleScholarGoogle Scholar |

Cooper JJ, Albentosa MJ (2003) Behavioural priorities of laying hens. Avian and Poultry Biology Reviews 14, 127–149.
Behavioural priorities of laying hens.Crossref | GoogleScholarGoogle Scholar |

Cooper JJ, Appleby MC (1996) Demand for nest boxes in laying hens. Behavioural Processes 36, 171–182.
Demand for nest boxes in laying hens.Crossref | GoogleScholarGoogle Scholar | 24896684PubMed |

Cooper JJ, Appleby MC (1997) Motivational aspects of individual variation in response to nestboxes by laying hens. Animal Behaviour 54, 1245–1253.
Motivational aspects of individual variation in response to nestboxes by laying hens.Crossref | GoogleScholarGoogle Scholar | 9398377PubMed |

Cooper JJ, Appleby MC (2003) The value of environmental resources to domestic hens: a comparison of the work-rate for food and for nests as a function of time. Animal Welfare 12, 39–52.

Craig JV, Craig JA (1985) Corticosteroid levels in White Leghorn hens as affected by handling, laying-house environment, and genetic stock. Poultry Science 64, 809–816.
Corticosteroid levels in White Leghorn hens as affected by handling, laying-house environment, and genetic stock.Crossref | GoogleScholarGoogle Scholar | 4001069PubMed |

Craig JV, Muir WM (1996) Group selection for adaptation to multiple-hen cages: beak-related mortality, feathering, and body weight responses. Poultry Science 75, 294–302.
Group selection for adaptation to multiple-hen cages: beak-related mortality, feathering, and body weight responses.Crossref | GoogleScholarGoogle Scholar | 8778719PubMed |

Craig JV, Craig JA, Vargas JV (1986) Corticosteroids and other indicators of hens’ well-being in four laying-house environments. Poultry Science 65, 856–863.
Corticosteroids and other indicators of hens’ well-being in four laying-house environments.Crossref | GoogleScholarGoogle Scholar | 3725724PubMed |

Cronin GM, Glatz PC (2020) Causes of feather pecking and subsequent welfare issues for the laying hen: a review. Animal Production Science.
Causes of feather pecking and subsequent welfare issues for the laying hen: a review.Crossref | GoogleScholarGoogle Scholar |

Cronin GM, Downing JA, Borg SS, Storey TH, Schirmer BN, Butler KL, Barnett JL (2008) The importance of nest-boxes to young adult laying hens: effects on stress physiology. World’s Poultry Science Journal 64, 243.

Dawkins MS (2003) Behaviour as a tool in the assessment of animal welfare. Zoology 106, 383–387.
Behaviour as a tool in the assessment of animal welfare.Crossref | GoogleScholarGoogle Scholar | 16351922PubMed |

Dawkins MS (2008) The science of animal suffering. Ethology 114, 937–945.
The science of animal suffering.Crossref | GoogleScholarGoogle Scholar |

de Haas EN, Bolhuis JE, de Jong IC, Kemp B, Janczak AM, Rodenburg TB (2014) Predicting feather damage in laying hens during the laying period. Is it the past or is it the present? Applied Animal Behaviour Science 160, 75–85.
Predicting feather damage in laying hens during the laying period. Is it the past or is it the present?Crossref | GoogleScholarGoogle Scholar |

de Jong IC, Wolthuis-Fillerup M, van Reenen CG (2007) Strength of preference for dustbathing and foraging substrates in laying hens. Applied Animal Behaviour Science 104, 24–36.
Strength of preference for dustbathing and foraging substrates in laying hens.Crossref | GoogleScholarGoogle Scholar |

de Jong ID, Gunnink H, Rommers JM, Bracke M (2013a) Effect of substrate during early rearing on floor-and feather pecking behaviour in young and adult laying hens. Archiv für Geflügelkunde 77, 15–22.

de Jong IC, Reuvekamp BFJ, Gunnink H (2013b) Can substrate in early rearing prevent feather pecking in adult laying hens? Animal Welfare 22, 305–314.
Can substrate in early rearing prevent feather pecking in adult laying hens?Crossref | GoogleScholarGoogle Scholar |

Duncan IJH, Hughes BO (1972) Free and operant feeding in domestic fowls. Animal Behaviour 20, 775–777.
Free and operant feeding in domestic fowls.Crossref | GoogleScholarGoogle Scholar |

Edwards LE, Hemsworth PH (2021) The impact of management, husbandry and stockperson decisions on the welfare of laying hens in Australia. Animal Production Science.
The impact of management, husbandry and stockperson decisions on the welfare of laying hens in Australia.Crossref | GoogleScholarGoogle Scholar |

Eklund B, Jensen P (2011) Domestication effects on behavioural synchronization and individual distances in chickens (Gallus gallus). Behavioural Processes 86, 250–256.
Domestication effects on behavioural synchronization and individual distances in chickens (Gallus gallus).Crossref | GoogleScholarGoogle Scholar | 21187131PubMed |

El-Lethey H, Aerni V, Jungi T, Wechsler B (2000) Stress and feather pecking in laying hens in relation to housing conditions. British Poultry Science 41, 22–28.
Stress and feather pecking in laying hens in relation to housing conditions.Crossref | GoogleScholarGoogle Scholar | 10821518PubMed |

El-Lethey H, Huber-Eicher B, Jungi TW (2003) Exploration of stress-induced immunosuppression in chickens reveals both stress-resistant and stress-susceptible antigen responses. Veterinary Immunology and Immunopathology 95, 91–101.
Exploration of stress-induced immunosuppression in chickens reveals both stress-resistant and stress-susceptible antigen responses.Crossref | GoogleScholarGoogle Scholar | 12963270PubMed |

Engel JM, Widowski TM, Tilbrook AJ, Butler KL, Hemsworth PH (2019) The effects of floor space and nest box access on the physiology and behavior of caged laying hens. Poultry Science 98, 533–547.
The effects of floor space and nest box access on the physiology and behavior of caged laying hens.Crossref | GoogleScholarGoogle Scholar | 30165652PubMed |

European Food Safety Authority (EFSA) (2005) The welfare aspects of various systems of keeping laying hens. EFSA Journal 197, 1–23.

Faure JM (1986) Operant determination of the cage and feeder size preferences of the laying hen. Applied Animal Behaviour Science 15, 325–336.
Operant determination of the cage and feeder size preferences of the laying hen.Crossref | GoogleScholarGoogle Scholar |

Faure JM (1991) Rearing conditions and needs for space and litter in laying hens. Applied Animal Behaviour Science 31, 111–117.
Rearing conditions and needs for space and litter in laying hens.Crossref | GoogleScholarGoogle Scholar |

Fossum O, Jansson DS, Etterlin PE, Vågsholm I (2009) Causes of mortality in laying hens in different housing systems in 2001 to 2004. Acta Veterinaria Scandinavica 51, 3
Causes of mortality in laying hens in different housing systems in 2001 to 2004.Crossref | GoogleScholarGoogle Scholar | 19146656PubMed |

Fraser D (2005) ‘Animal welfare and the intensification of animal production: an alternative interpretation.’ FAO Readings in Ethics, 2. (Food & Agriculture Organisation: Rome)

Fraser D, Nicol CJ (2018) Preference and motivation research. In ‘Animal welfare’. (Eds MC Appleby, IAS Olsson, F Galindo) pp. 213–231. (CAB International: Wallingford, UK)

Gebhardt-Henrich SG, Stratmann A (2016) What is causing smothering in laying hens? The Veterinary Record 179, 250–251.
What is causing smothering in laying hens?Crossref | GoogleScholarGoogle Scholar | 27609962PubMed |

Gregory NG, Wilkins LJ (1989) Broken bones in domestic fowl: handling and processing damage in end‐of‐lay battery hens. British Poultry Science 30, 555–562.
Broken bones in domestic fowl: handling and processing damage in end‐of‐lay battery hens.Crossref | GoogleScholarGoogle Scholar | 2819499PubMed |

Gregory NG, Wilkins LJ, Eleperuma SD, Ballantyne AJ, Overfield ND (1990) Broken bones in domestic fowls: effect of husbandry system and stunning method in end‐of‐lay hens. British Poultry Science 31, 59–69.
Broken bones in domestic fowls: effect of husbandry system and stunning method in end‐of‐lay hens.Crossref | GoogleScholarGoogle Scholar |

Gregory NG, Wilkins LJ, Austin SD, Belyavin CG, Alvey DM, Tucker SA (1992) Effect of catching method on the prevalence of broken bones in end of lay hens. Avian Pathology 21, 717–722.
Effect of catching method on the prevalence of broken bones in end of lay hens.Crossref | GoogleScholarGoogle Scholar | 18670991PubMed |

Gross WB, Siegel PB, DuBose RT (1980) Some effects of feeding corticosterone to chickens. Poultry Science 59, 516–522.
Some effects of feeding corticosterone to chickens.Crossref | GoogleScholarGoogle Scholar |

Guarino M, Caroli A, Navarotto P (1999) Dust concentration and mortality distribution in an enclosed laying house. Transactions of the ASAE. American Society of Agricultural Engineers 42, 1127–1134.
Dust concentration and mortality distribution in an enclosed laying house.Crossref | GoogleScholarGoogle Scholar |

Guesdon V, Leterrier C, Constantin P, Guémené D, Couty M, Faure JM (2004) Humeral quality and adrenal responsiveness in laying hens reared in standard and furnished cages. Animal Research 53, 235–243.
Humeral quality and adrenal responsiveness in laying hens reared in standard and furnished cages.Crossref | GoogleScholarGoogle Scholar |

Harrison R (1964) ‘Animal machines.’ (Stuart: London)

Hartcher KM, Jones B (2017) The welfare of layer hens in cage and cage-free housing systems. World’s Poultry Science Journal 73, 767–781.
The welfare of layer hens in cage and cage-free housing systems.Crossref | GoogleScholarGoogle Scholar |

Hartcher KM, Wilkinson SJ, Hemsworth PH, Cronin GM (2016) Severe feather-pecking in non-cage laying hens and some associated and predisposing factors: a review. World’s Poultry Science Journal 72, 103–114.
Severe feather-pecking in non-cage laying hens and some associated and predisposing factors: a review.Crossref | GoogleScholarGoogle Scholar |

Hartini S, Choct M, Hinch G, Kocher A, Nolan JV (2002) Effects of light intensity during rearing and beak trimming and dietary fiber sources on mortality, egg production, and performance of ISA brown laying hens. Journal of Applied Poultry Research 11, 104–110.
Effects of light intensity during rearing and beak trimming and dietary fiber sources on mortality, egg production, and performance of ISA brown laying hens.Crossref | GoogleScholarGoogle Scholar |

Hemsworth PH (2018) Key determinants of pig welfare: implications of animal management and housing design on livestock welfare. Animal Production Science 58, 1375–1386.
Key determinants of pig welfare: implications of animal management and housing design on livestock welfare.Crossref | GoogleScholarGoogle Scholar |

Hemsworth PH, Edwards LE (2020) Natural behaviours, their drivers and their implications for laying hen welfare. Animal Production Science.
Natural behaviours, their drivers and their implications for laying hen welfare.Crossref | GoogleScholarGoogle Scholar |

Hemsworth PH, Mellor DJ, Cronin GM, Tilbrook AJ (2015) Scientific assessment of animal welfare. New Zealand Veterinary Journal 63, 24–30.
Scientific assessment of animal welfare.Crossref | GoogleScholarGoogle Scholar | 25263963PubMed |

Hetland H, Moe RO, Tauson R, Lervik S, Svihus B (2004) Effect of including whole oats into pellets on performance and plumage condition in laying hens housed in conventional and furnished cages. Acta Agriculturae Scandinavica Section a. Animal Science 54, 206–212.

Huber-Eicher B, Wechsler B (1997) Feather pecking in domestic chicks: its relation to dustbathing and foraging. Animal Behaviour 54, 757–768.
Feather pecking in domestic chicks: its relation to dustbathing and foraging.Crossref | GoogleScholarGoogle Scholar | 9344430PubMed |

Huber-Eicher B, Wechsler B (1998) The effect of quality and availability of foraging materials on feather pecking in laying hen chicks. Animal Behaviour 55, 861–873.
The effect of quality and availability of foraging materials on feather pecking in laying hen chicks.Crossref | GoogleScholarGoogle Scholar | 9632473PubMed |

Hughes BO (1983) Space requirements in poultry. In ‘Farm animal housing and welfare’. (Eds SH Baxter, MR Baxter, JAC MacCormack) pp. 121–128. (Martinus Nijhoff: The Hague, The Netherlands)

Hughes AL, Buitenhuis AJ (2010) Reduced variance of gene expression at numerous loci in a population of chickens selected for high feather pecking. Poultry Science 89, 1858–1869.
Reduced variance of gene expression at numerous loci in a population of chickens selected for high feather pecking.Crossref | GoogleScholarGoogle Scholar | 20709970PubMed |

Huneau-Salaün A, Guinebretière M, Taktak A, Huonnic D, Michel V (2011) Furnished cages for laying hens: study of the effects of group size and litter provision on laying location, zootechnical performance and egg quality. Animal 5, 911–917.
Furnished cages for laying hens: study of the effects of group size and litter provision on laying location, zootechnical performance and egg quality.Crossref | GoogleScholarGoogle Scholar | 22440030PubMed |

Jalal MA, Scheideler SE, Marx D (2006) Effect of bird cage space and dietary metabolizable energy level on production parameters in laying hens1. Poultry Science 85, 306–311.
Effect of bird cage space and dietary metabolizable energy level on production parameters in laying hens1.Crossref | GoogleScholarGoogle Scholar | 16523631PubMed |

Jones DR, Cox NA, Guard J, Fedorka-Cray PJ, Buhr RJ, Gast RK, Abdo Z, Rigsby LL, Plumblee JR, Karcher DM, Robison CI, Blatchford RA, Makagon MM (2015) Microbiological impact of three commercial laying hen housing systems. Poultry Science 94, 544–551.
Microbiological impact of three commercial laying hen housing systems.Crossref | GoogleScholarGoogle Scholar | 25480737PubMed |

Jongman EC (2021) Rearing conditions of laying hens and welfare during the laying phase. Animal Production Science
Rearing conditions of laying hens and welfare during the laying phase.Crossref | GoogleScholarGoogle Scholar |

Kang HK, Park SB, Kim SH, Kim CH (2016) Effects of stock density on the laying performance, blood parameter, corticosterone, litter quality, gas emission and bone mineral density of laying hens in floor pens. Poultry Science 95, 2764–2770.
Effects of stock density on the laying performance, blood parameter, corticosterone, litter quality, gas emission and bone mineral density of laying hens in floor pens.Crossref | GoogleScholarGoogle Scholar | 27578881PubMed |

Koelkebeck KW, Cain JR (1984) Performance, behavior, plasma corticosterone, and economic returns of laying hens in several management alternatives. Poultry Science 63, 2123–2131.
Performance, behavior, plasma corticosterone, and economic returns of laying hens in several management alternatives.Crossref | GoogleScholarGoogle Scholar | 6514660PubMed |

Koelkebeck KW, Cain JR, Amoss MS (1986) Corticosterone sampling of laying hens in different management systems. Poultry Science 65, 183–185.
Corticosterone sampling of laying hens in different management systems.Crossref | GoogleScholarGoogle Scholar | 3754334PubMed |

Koelkebeck KW, Amoss MS, Cain JR (1987) Production, physiological, and behavioral responses of laying hens in different management environments. Poultry Science 66, 397–407.
Production, physiological, and behavioral responses of laying hens in different management environments.Crossref | GoogleScholarGoogle Scholar | 3601849PubMed |

Lambton SL, Knowles TG, Yorke C, Nicol CJ (2010) The risk factors affecting the development of gentle and severe feather pecking in loose housed laying hens. Applied Animal Behaviour Science 123, 32–42.
The risk factors affecting the development of gentle and severe feather pecking in loose housed laying hens.Crossref | GoogleScholarGoogle Scholar |

Lambton SL, Knowles TG, Yorke C, Nicol CJ (2015) The risk factors affecting the development of vent pecking and cannibalism in free-range and organic laying hens. Animal Welfare 24, 101–111.
The risk factors affecting the development of vent pecking and cannibalism in free-range and organic laying hens.Crossref | GoogleScholarGoogle Scholar |

Lay DC, Fulton RM, Hester PJ, Karcher DM, Kjaer JB, Mench JA, Mullens BA, Newberry RC, Nicol CJ, O’Sullivan NP (2011) Hen welfare in different housing systems. Poultry Science 90, 278–294.
Hen welfare in different housing systems.Crossref | GoogleScholarGoogle Scholar | 21177469PubMed |

LayWel (2006) ‘Results of the European project SSPE-CT-2004-502315: welfare implications of changes in production systems for laying hens.’ (European Union). Available at http://www.laywel.eu/ [Verified 8 October 2019]

Lee K, Moss CW (1995) Effects of population density on layer performance. Poultry Science 74, 1754–1760.
Effects of population density on layer performance.Crossref | GoogleScholarGoogle Scholar | 8614684PubMed |

Manteuffel G, Langbein J, Puppe B (2009) From operant learning to cognitive enrichment in farm animal housing: bases and applicability. Animal Welfare Science 18, 87–95.

Marino L (2017) Thinking chickens: a review of cognition, emotion, and behaviour in the domestic chicken. Animal Cognition 20, 127–147.
Thinking chickens: a review of cognition, emotion, and behaviour in the domestic chicken.Crossref | GoogleScholarGoogle Scholar | 28044197PubMed |

Mashaly MM, Webb MM, Youtz SL, Roush WB, Graves HB (1984) Changes in serum corticosterone concentration of laying hens as a response to increased population density. Poultry Science 63, 2271–2274.
Changes in serum corticosterone concentration of laying hens as a response to increased population density.Crossref | GoogleScholarGoogle Scholar | 6514670PubMed |

Mason GJ (2006) Stereotypic behaviour in captive animals: fundamentals and implications for welfare and beyond. In ‘Stereotypic animal behaviour: fundamentals and applications to welfare’. (Eds G Mason, J Rushen) pp. 325–357. (CABI Publishing: Wallingford, UK)

Mason GJ, Burn CC (2018) Frustration and boredom in impoverished environments. In ‘Animal welfare’. 3rd edn. (Eds MC Appleby, IAS Olsson, F Galindo) pp. 114–138. (CABI Publishing: Wallingford, UK)

Mason GJ, Latham N (2004) Can’t stop, won’t stop: is stereotypy a reliable animal welfare indicator? Animal Welfare 13, S57–S69.

Matthews LR, Hemsworth PH (2012) Drivers of change: law, international markets, and policy. Animal Frontiers 2, 40–45.
Drivers of change: law, international markets, and policy.Crossref | GoogleScholarGoogle Scholar |

Mellor DJ, Stafford K (2004) Animal welfare implications of neonatal mortality and morbidity in farm animals. Veterinary Journal 168, 118–133.
Animal welfare implications of neonatal mortality and morbidity in farm animals.Crossref | GoogleScholarGoogle Scholar |

Mellor DJ, Patterson-Kane E, Stafford KJ (2009) ‘The sciences of animal welfare.’ (John Wiley & Sons: Oxford, UK)

Mench J, Van Tienhoven A, Marsh J, McCormick C, Cunningham D, Baker R (1986) Effects of cage and floor pen management on behavior, production, and physiological stress responses of laying hens. Poultry Science 65, 1058–1069.

Meng F, Chen D, Li X, Li J, Bao J (2015) Effects of large or small furnished cages on performance, welfare and egg quality of laying hens. Animal Production Science 55, 793–798.
Effects of large or small furnished cages on performance, welfare and egg quality of laying hens.Crossref | GoogleScholarGoogle Scholar |

Moberg GP (2000) Biological response to stress: implications for animal welfare. In ‘The biology of animal stress; basic principles and applications for animal welfare’. (Eds GP Moberg, GA Mench) pp. 1–21. (CABI Publishing: Wallingford, UK)

Moe RO, Guemene D, Bakken M, Larsen HJS, Shini S, Lervik S, Skjerve E, Michel V, Tauson R (2010) Effects of housing conditions during the rearing and laying period on adrenal reactivity, immune response and heterophil to lymphocyte (H/L) ratios in laying hens. Animal 4, 1709–1715.
Effects of housing conditions during the rearing and laying period on adrenal reactivity, immune response and heterophil to lymphocyte (H/L) ratios in laying hens.Crossref | GoogleScholarGoogle Scholar | 22445125PubMed |

Moinard C, Morisse JP, Faure JM (1998) Effect of cage area, cage height and perches on feather condition, bone breakage and mortality of laying hens. British Poultry Science 39, 198–202.
Effect of cage area, cage height and perches on feather condition, bone breakage and mortality of laying hens.Crossref | GoogleScholarGoogle Scholar | 9649871PubMed |

Newberry RC (2004) Cannibalism. In ‘Welfare of the laying hen’. (Ed. GC Perry) pp. 239–258. (CABI Publishing: Wallingford, UK)

Newberry RC, Estevez I, Keeling LJ (2001) Group size and perching behaviour in young domestic fowl. Applied Animal Behaviour Science 73, 117–129.
Group size and perching behaviour in young domestic fowl.Crossref | GoogleScholarGoogle Scholar | 11358609PubMed |

Newberry RC, Keeling LJ, Estevez I, Bilčík B (2007) Behaviour when young as a predictor of severe feather pecking in adult laying hens: the redirected foraging hypothesis revisited. Applied Animal Behaviour Science 107, 262–274.
Behaviour when young as a predictor of severe feather pecking in adult laying hens: the redirected foraging hypothesis revisited.Crossref | GoogleScholarGoogle Scholar |

Nicol C, Lindberg AC, Phillips AJ, Pope SJ, Wilkins LJ, Green LE (2001) Influence of prior exposure to wood shavings on feather pecking, dustbathing and foraging in adult laying hens. Applied Animal Behaviour Science 73, 141–155.
Influence of prior exposure to wood shavings on feather pecking, dustbathing and foraging in adult laying hens.Crossref | GoogleScholarGoogle Scholar | 11358611PubMed |

Nicol CJ, Brown SN, Glen E, Pope SJ, Short FJ, Warriss PD, Zimmerman PH, Wilkins LJ (2006) Effects of stocking density, flock size and management on the welfare of laying hens in single-tier aviaries. British Poultry Science 47, 135–146.
Effects of stocking density, flock size and management on the welfare of laying hens in single-tier aviaries.Crossref | GoogleScholarGoogle Scholar | 16641024PubMed |

Nicol CJ, Bouwsema J, Caplen G, Davies AC, Hockenhull J, Lambton SL, Lines JA, Mullan S, Weeks CA (2017) ‘Farmed bird welfare science review.’ (Department of Economic Development, Jobs, Transport and Resources Victoria: Melbourne, Vic., Australia)

Olsson IAS, Keeling LJ (2000) Night-time roosting in laying hens and the effect of thwarting access to perches. Applied Animal Behaviour Science 68, 243–256.
Night-time roosting in laying hens and the effect of thwarting access to perches.Crossref | GoogleScholarGoogle Scholar |

Olsson IAS, Keeling LJ (2002) The push-door for measuring motivation in hens: laying hens are motivated to perch at night. Animal Welfare 11, 11–19.

Onbaşılar EE, Aksoy FT (2005) Stress parameters and immune response of layers under different cage floor and density conditions. Livestock Production Science 95, 255–263.
Stress parameters and immune response of layers under different cage floor and density conditions.Crossref | GoogleScholarGoogle Scholar |

Pedersen AF, Zachariae R, Bovbjerg DH (2009) Psychological stress and antibody response to influenza vaccination: a meta-analysis. Brain, Behavior, and Immunity 23, 427–433.
Psychological stress and antibody response to influenza vaccination: a meta-analysis.Crossref | GoogleScholarGoogle Scholar | 19486657PubMed |

Petek M, McKinstry JL (2010) Reducing the prevalence and severity of injurious pecking in laying hens without beak trimming. Uludag University Journal of the Faculty of Veterinary Medicine 29, 61–68.

Pohle K, Cheng H-W (2009) Comparative effects of furnished and battery cages on egg production and physiological parameters in White Leghorn hens. Poultry Science 88, 2042–2051.
Comparative effects of furnished and battery cages on egg production and physiological parameters in White Leghorn hens.Crossref | GoogleScholarGoogle Scholar | 19762855PubMed |

Post JJ, Rebel JM, Ter Huurne AA (2003) Physiological effects of elevated plasma corticosterone concentrations in broiler chickens. An alternative means by which to assess the physiological effects of stress. Poultry Science 82, 1313–1318.
Physiological effects of elevated plasma corticosterone concentrations in broiler chickens. An alternative means by which to assess the physiological effects of stress.Crossref | GoogleScholarGoogle Scholar |

Pötzsch CJ, Lewis K, Nicol CJ, Green LE (2001) A cross-sectional study of the prevalence of vent pecking in laying hens in alternative systems and its associations with feather pecking, management and disease. Applied Animal Behaviour Science 74, 259–272.
A cross-sectional study of the prevalence of vent pecking in laying hens in alternative systems and its associations with feather pecking, management and disease.Crossref | GoogleScholarGoogle Scholar |

Ralph CR, Hemsworth PH, Leury BJ, Tilbrook AJ (2015) Relationship between plasma and tissue corticosterone in laying hens (Gallus gallus domesticus): implications for stress physiology and animal welfare. Domestic Animal Endocrinology 50, 72–82.
Relationship between plasma and tissue corticosterone in laying hens (Gallus gallus domesticus): implications for stress physiology and animal welfare.Crossref | GoogleScholarGoogle Scholar | 25447882PubMed |

Rayner AC, Gill R, Brass D, Willings TH, Bright A (2016) Smothering in UK free-range flocks. Part 2: investigating correlations between disease, housing and management practices. The Veterinary Record 179, 252
Smothering in UK free-range flocks. Part 2: investigating correlations between disease, housing and management practices.Crossref | GoogleScholarGoogle Scholar | 27353872PubMed |

Rodenburg TB, Tuyttens FA, Sonck B, De Reu K, Herman L, Zoons J (2005) Welfare, health, and hygiene of laying hens housed in furnished cages and in alternative housing systems. Journal of Applied Animal Welfare Science 8, 211–226.
Welfare, health, and hygiene of laying hens housed in furnished cages and in alternative housing systems.Crossref | GoogleScholarGoogle Scholar | 16468949PubMed |

Rodenburg TB, Tuyttens FAM, De Reu K, Herman L, Zoons J, Sonck B (2008) Welfare assessment of laying hens in furnished cages and non-cage systems: an on-farm comparison. Animal Welfare 17, 363–373.

Rodenburg TB, Van Krimpen MM, De Jong IC, De Haas EN, Kops MS, Riedstra BJ, Nordquist RE, Wagenaar JP, Bestman M, Nicol CJ (2013) The prevention and control of feather pecking in laying hens: identifying the underlying principles. World’s Poultry Science Journal 69, 361–374.
The prevention and control of feather pecking in laying hens: identifying the underlying principles.Crossref | GoogleScholarGoogle Scholar |

Roush WB, Mashaly MM, Graves HB (1984) Effect of increased bird population in a fixed cage area on production and economic responses of single comb White Leghorn laying hens. Poultry Science 63, 45–48.
Effect of increased bird population in a fixed cage area on production and economic responses of single comb White Leghorn laying hens.Crossref | GoogleScholarGoogle Scholar | 6701142PubMed |

Rushen J (2017) Housing and the welfare of dairy cattle. In ‘Achieving sustainable milk production’. Vol. 3. (Eds J Webster, D Burleigh) pp. 53–79. (Burleigh Dodds Science Publishing: Cambridge, UK)

Rushen J, Passillé AMB (1992) The scientific assessment of the impact of housing on animal welfare: a critical review. Canadian Journal of Animal Science 72, 721–743.
The scientific assessment of the impact of housing on animal welfare: a critical review.Crossref | GoogleScholarGoogle Scholar |

Savory CJ, Jack MC, Sandilands V (2006) Behavioural responses to different floor space allowances in small groups of laying hens. British Poultry Science 47, 120–124.
Behavioural responses to different floor space allowances in small groups of laying hens.Crossref | GoogleScholarGoogle Scholar | 16641021PubMed |

Scholz B, Ronchen S, Hamann H, Pendl H, Distl O (2008) Effect of housing system, group size and perch position on H/L ratio in laying hens Archiv für Geflügelkunde 72, 174–180.

Scholz B, Rönchen S, Hamann H (2009) Bone strength and keel bone status of two layer strains kept in small group housing systems with different perch configurations and group sizes. Berliner und Munchener Tierarztliche Wochenschrift 122, 249–256.

Sherwin CM, Richards GJ, Nicol CJ (2010) Comparison of the welfare of layer hens in 4 housing systems in the UK. British Poultry Science 51, 488–499.
Comparison of the welfare of layer hens in 4 housing systems in the UK.Crossref | GoogleScholarGoogle Scholar | 20924842PubMed |

Shimmura T, Eguchi Y, Uetake K, Tanaka T (2007) Behavior, performance and physical condition of laying hens in conventional and small furnished cages. Animal Science Journal 78, 323–329.
Behavior, performance and physical condition of laying hens in conventional and small furnished cages.Crossref | GoogleScholarGoogle Scholar |

Shimmura T, Hirahara S, Azuma T, Suzuki T, Eguchi Y, Uetake K, Tanaka T (2010) Multi-factorial investigation of various housing systems for laying hens. British Poultry Science 51, 31–42.
Multi-factorial investigation of various housing systems for laying hens.Crossref | GoogleScholarGoogle Scholar | 20390567PubMed |

Shini S (2003) Physiological responses of laying hens to the alternative housing systems. International Journal of Poultry Science 2, 357–360.
Physiological responses of laying hens to the alternative housing systems.Crossref | GoogleScholarGoogle Scholar |

Singh M, Ruhnke I, de Koning C, Drake K, Skerman AG, Hinch GN, Glatz PC (2017) Demographics and practices of semi-intensive free-range farming systems in Australia with an outdoor stocking density of ≤ 1500 hens/hectare. PLoS One 12, e0187057
Demographics and practices of semi-intensive free-range farming systems in Australia with an outdoor stocking density of ≤ 1500 hens/hectare.Crossref | GoogleScholarGoogle Scholar | 29206228PubMed |

Sohail SS, Bryant MM, Roland DA (2004) Effect of reducing cage density on performance and economics of second-cycle (force rested) commercial Leghorns. Journal of Applied Poultry Research 13, 401–405.
Effect of reducing cage density on performance and economics of second-cycle (force rested) commercial Leghorns.Crossref | GoogleScholarGoogle Scholar |

Sutton JR, Casey JH (1975) The adrenocortical response to competitive athletics in veteran athletes. The Journal of Clinical Endocrinology and Metabolism 40, 135–138.
The adrenocortical response to competitive athletics in veteran athletes.Crossref | GoogleScholarGoogle Scholar | 1112872PubMed |

Szechtman H, Lambrou PJ, Caggiula AR, Redgate ES (1974) Plasma corticosterone levels during sexual behavior in male rats. Hormones and Behavior 5, 191–200.
Plasma corticosterone levels during sexual behavior in male rats.Crossref | GoogleScholarGoogle Scholar | 4847187PubMed |

Tauson R, Holm KE (2002) Evaluation of Victorsson furnished cage for 8 laying hens according to the #7 Swedish Animal Welfare Ordinance and according to the New-Technique Evaluation Program at the Swedish Board of Agriculture. Report 251. Swedish University of Agricultural Sciences, Department of Animal Nutrition and Management, Uppsala, Sweden.

Tilbrook AJ, Fisher AD (2020) Stress, health and the welfare of laying hens. Animal Production Science.
Stress, health and the welfare of laying hens.Crossref | GoogleScholarGoogle Scholar |

Tilbrook AJ, Ralph CR (2018) Hormones, stress and the welfare of animals. Animal Production Science 58, 408–415.
Hormones, stress and the welfare of animals.Crossref | GoogleScholarGoogle Scholar |

Turner AI, Keating CL, Tilbrook AJ (2012) Sex differences and the role of sex steroids in sympatho-adrenal medullary system and hypothalamo–pituitary adrenal axis responses to stress. In ‘Sex steroids’. (Ed. SM Kahn) pp. 115–136. (Tech Publishing: Rijeka, Croatia)

Underwood G, Andrews D, Phung T (2021) Advances in genetic selection and breeder practice improve commercial layer hen welfare. Animal Production Science
Advances in genetic selection and breeder practice improve commercial layer hen welfare.Crossref | GoogleScholarGoogle Scholar | (In press).

Wall H (2011) Production performance and proportion of nest eggs in layer hybrids housed in different designs of furnished cages. Poultry Science 90, 2153–2161.
Production performance and proportion of nest eggs in layer hybrids housed in different designs of furnished cages.Crossref | GoogleScholarGoogle Scholar | 21933995PubMed |

Weeks CA, Nicol CJ (2006) Behavioural needs, priorities and preferences of laying hens. World’s Poultry Science Journal 62, 296–307.
Behavioural needs, priorities and preferences of laying hens.Crossref | GoogleScholarGoogle Scholar |

Weeks CA, Lambton SL, Williams AG (2016) Implications for welfare, productivity and sustainability of the variation in reported levels of mortality for laying hen flocks kept in different housing systems: a meta-analysis of ten studies. PLoS One 11, e0146394
Implications for welfare, productivity and sustainability of the variation in reported levels of mortality for laying hen flocks kept in different housing systems: a meta-analysis of ten studies.Crossref | GoogleScholarGoogle Scholar | 26734933PubMed |

Weimer SL, Robison CI, Tempelman RJ, Jones DR, Karcher DM (2019) Laying hen production and welfare in enriched colony cages at different stocking densities. Poultry Science 98, 3578–3586.
Laying hen production and welfare in enriched colony cages at different stocking densities.Crossref | GoogleScholarGoogle Scholar | 30938804PubMed |

Weitzenbürger D, Vits A, Hamann H, Distl O (2005) Effect of furnished small group housing systems and furnished cages on mortality and causes of death in two layer strains. British Poultry Science 46, 553–559.
Effect of furnished small group housing systems and furnished cages on mortality and causes of death in two layer strains.Crossref | GoogleScholarGoogle Scholar | 16359107PubMed |

Wichman A, Keeling LJ (2009) The influence of losing or gaining access to peat on the dustbathing behaviour of laying hens. Animal Welfare 18, 149–157.

Widowski TM, Hemsworth PH (2008) Housing hens to suit their needs. In ‘Proceedings of the XXIII world poultry congress’, 30 June–4 July 2008, Brisbane, Qld, Australia. p. 241.

Widowski TM, Hemsworth PH, Barnett JL, Rault J-L (2016) Laying hen welfare I. Social environment and space. World’s Poultry Science Journal 72, 333–342.
Laying hen welfare I. Social environment and space.Crossref | GoogleScholarGoogle Scholar |

Widowski TM, Caston LJ, Hunniford ME, Cooley L, Torrey S (2017a) Effect of space allowance and cage size on laying hens housed in furnished cages. Part I: performance and well-being. Poultry Science 96, 3805–3815.
Effect of space allowance and cage size on laying hens housed in furnished cages. Part I: performance and well-being.Crossref | GoogleScholarGoogle Scholar | 29050408PubMed |

Widowski TM, Caston LJ, Casey-Trott TM, Hunniford M (2017b) The effect of space allowance and cage size on laying hens housed in furnished cages. Part II: behavior at the feeder. Poultry Science 96, 3816–3823.
The effect of space allowance and cage size on laying hens housed in furnished cages. Part II: behavior at the feeder.Crossref | GoogleScholarGoogle Scholar | 29050409PubMed |

Wilkins LJ, McKinstry JL, Avery NC, Knowles TG, Brown SN, Tarlton J, Nicol CJ (2011) Influence of housing system and design on bone strength and keel bone fractures in laying hens. The Veterinary Record 169, 414
Influence of housing system and design on bone strength and keel bone fractures in laying hens.Crossref | GoogleScholarGoogle Scholar | 21862469PubMed |

Yilmaz Dikmen B, İpek A, Şahan Ü, Petek M, Sözcü A (2016) Egg production and welfare of laying hens kept in different housing systems (conventional, enriched cage, and free-range). Poultry Science 95, 1564–1572.
Egg production and welfare of laying hens kept in different housing systems (conventional, enriched cage, and free-range).Crossref | GoogleScholarGoogle Scholar | 26994200PubMed |

Yue S, Duncan IJH (2003) Frustrated nesting behaviour: relation to extra-cuticular shell calcium and bone strength in White Leghorn hens. British Poultry Science 44, 175–181.
Frustrated nesting behaviour: relation to extra-cuticular shell calcium and bone strength in White Leghorn hens.Crossref | GoogleScholarGoogle Scholar | 12828201PubMed |