An evaluation of different chicken housing systems


ESR blog


Major policy changes in Europe, North America and recently New Zealand to improve animal welfare led to an increased number of chickens kept in alternative housing systems instead of cages. We asked consumers through a social media poll to give their opinion on what is considered most important when choosing a chicken product based on the production system. Based on the results (30 votes), consumers prefer products from chickens that have been raised in a production system where their health is prioritized. The second priority of the consumers is product safety. Some consumers also put emphasis on the chickens’ ability to behave naturally in the production system used.  

In this blog, we evaluate how the housing systems may impact the health, product safety, and behavior of chickens.

The results of the LinkedIn poll


When evaluating free-range poultry systems, increased contact with pathogens should be taken into account. In a free-range system the environment is not controlled or only partially controlled, which makes transmission of diseases more likely. McMullin (2022) reviewed the prevalence and severity of infectious diseases across the different poultry housing systems. While higher risk for viruses like New-Castle and avian influenza can be expected, the range of biosecurity measures will make the difference, not the fact that the chickens have an outdoor area. Endemic bacterial infections with E. coli, Gallibacterium, erysipelas and others were found to be higher in free-range systems and lower in cages. Another notable example would be soil-transmitted helminths which are a re-emerging infection across the countries that have adopted the free-range system (Sherwin et al. 2013). It can be argued that the co-existence of pathogens with chickens is a natural phenomenon and that is how things exist in the wild. For example, chickens in free-range systems do not always show clinical symptoms (Sharma et al. 2018) or a reduction in egg production to infections with Ascarids (Sherwin et al. 2013), leading to the assumption that the birds cope just fine. On the other hand, it is difficult to ascertain if birds infected with pathogens are under any sort of pain especially when there are no clear clinical signs. Shimmura et al. (2010) however showed that birds raised in a free-range system had the lowest score for freedom of pain, diseases and injury compared to cage system, although immune response was higher in birds kept in a free-range production system.  

Furthermore, the type of birds in each production system influences their adaptability as well as the resilience (Castellini et al. 2016). Slow-growing breeds and high producing breeds of birds are different in their anatomy and genetics. Commercial birds have been selected for high productivity over decades, implying that they have become less resilient to infections given the negative correlation between health and productivity. The more energy and resources are used for production, the less is available for fighting pathogens. Conflicting with this, however, lower worm burden and shedding of eggs was found in commercial birds (Lohmann brown) compared to Danish Landrace (Permin and Ranvig 2001), but this study is now over 20 years old, and the genotype has changed a lot. The increased exposure to pathogens is not the only thing that threatens the health of birds in a free-range system. The increased exposure to pathogens is not the only thing that threatens the health of birds in a free-range system. For instance, also cases of increased cannibalism (e.g., feather pecking) and of nutrient deficiency have been reported in free-ranged birds.

Food Safety

Food safety is another important aspect of consideration in the evaluation of poultry housing systems and, as shown in the result of our poll, is important to consumers. Studies have found that the prevalence of certain zoonotic infections is considerably affected by the production system. The most common zoonotic pathogens in poultry are Campylobacter and Salmonella and are known to be transmitted to humans mainly via poultry meat and eggs (Iannette et al. 2020). According to the “European Union One Health 2021 Zoonoses Report in 2021”, a total of 127,840 and 60,050 human cases related to campylobacteriosis and salmonellosis, respectively, were observed in the European Union (EFSA 2022).  These pathogens will also cause antigen stress to the birds, thereby compromising their welfare (Campylobacter: Awad et al., 2017 and Salmonella: Ijas et al., 2021). Therefore, controlling these pathogens is important in terms of product safety and animal welfare in poultry production. However, previous studies reported contrasting results related to the prevalence of Campylobacter contamination of broiler meat from alternative farming systems vs. conventional farming systems. Heuer et al. (2001) and Rosenquist et al. (2013) reported that Campylobacter contamination in broiler meat was higher in organic farms than that of conventional farms while Lücke (2017) reported that although the prevalence was higher in live birds of free-range systems, Campylobacter contamination in meat was similar to that of the conventional farms. Interestingly, much research conducted in Europe indicated that Salmonella incidences in free-range broilers and layers are lower than that of conventional farms as reviewed by Holt (2021). However, this author claims that the free-range farms are relatively new and the accumulation of Salmonella in soil in free-range system can occur over time which can possibly give rise to a change in results in future. As Sosnowski and Osek (2021) reviewed, prevalence of Shiga toxin producing E. coli, Staphylococcus aureus and Listeria monocytogenes pathogens in alternative farming systems also were lower than or equal to that of conventional farms. However, the breeds of the poultry, housing facilities (access to wild birds and animals) and management (deworming, prophylaxis etc.) might be different in the farms used among the above experiments. Therefore, with these contrasting results, it is difficult to conclude about the microbial safety of the products from alternative systems compared to conventional production systems.  

Also in egg production, bacteria like E. coli, Campylobacter sp. and especially Salmonella enterica are a concern. In free range systems, the birds have closer contact to wildlife, which increases the risk of introduction of pathogens (Holt et al. 2021). However, studies did not clearly show a higher prevalence of foodborne pathogens in alternative housing systems compared to cages: a higher prevalence of Salmonella sp. in cage systems was reported by Methner et al. (2006), while De Vylder et al. (2011) found a trend for higher horizontal transmission of Salmonella enterica serovar Enteritidis between hens housed in an aviary system compared to a cage and a floor system. A higher prevalence of Campylobacter sp. was reported for laying hens from alternative housing systems, but the difference was not statistically significant (Rama et al. 2018). Therefore, there is presently no clear evidence for a higher risk of food-borne pathogens in alternative housing systems for laying hens.

However, when the birds have access to the outdoors, it is obvious that they will be exposed to other uncontrolled environmental factors such as ambient temperature fluctuations, predators, contaminants from wild animals as well as contaminants in soil. As reviewed by Holt (2021), many studies have demonstrated that the dioxin (toxic industrial contaminants from soil) content in eggs from free range chickens are higher than that of conventional farms. Therefore, in terms of the safety of products, multiple factors must be considered in alternative farming systems. Strategies like maintaining strict biosecurity even in outdoor environment, proper maintenance of the housing system to avoid unnecessary predation and mortality, prophylaxis and early microbiome reprograming can be identified as strategies to overcome these adverse effects related to food safety from the alternative production systems. Thus, more applied research is necessary in future to ensure the product safety and welfare of the birds in these systems


The freedom to follow the natural and species-specific behavior is an important aspect of animal welfare (Fraser 2008). Key behavior elements for a laying hen include grooming (preening, dust bathing, stretching), perching, foraging, and nesting. Most of these are not possible in a conventional cage system, which is not in use in the EU anymore, and extremely limited in an enriched cage system. The stimuli provided in an enriched cage are few and do not elicit a lot of foraging and exploring activity. An aviary provides more stimuli, while the free-range systems provide the highest amount and diversity of stimuli, enabling the hens to forage and explore. The natural light containing an UV portion allows for natural perception of the surroundings. Often though, the surroundings of the stable are barren and deprived of stimuli due to intensive use by scratching and pecking. To increase the use of the whole outdoor area, enrichment like bushes, trees or artificial covers must be provided, which make the hens feel more secure (Knierim et al. 2006). Roosters can also provide security to the hens. Furthermore, the hens can seek fresh air to escape high dust and ammonia levels in the stable, which is not possible in an aviary, where dust and ammonia levels can be high due to the activity of the hens and the lack of separation from their excretions (Knierim et al. 2006).  More fearful and distressed behavior has been observed in caged housing while hens in outdoor systems showed more comfort behavior and were less fearful (Nenadovic et al. 2022). Furthermore, a better plumage has been observed in hens with outdoor access indicating less injurious behavior and the possibility to escape antagonistic behavior (Rodenburg et al. 2013, Sosnówka-Czajka et al. 2021). 

Perching is possible to a limited degree in enriched cages, but the positioning in a confined environment can lead to injuries due to collision and cloacal pecking (Hartcher and Jones 2017). The multiple levels in an aviary or free-range system provide ample opportunity to perch, which is especially used at night (Fraser et al. 2013, Sosnówka-Czajka et al. 2021). The opportunity to perch increases the hens’ feeling of security and provides exercise (Donaldson and O’Connell 2012, Yan et al. 2014). It is important that pullets are acquainted with the use of multiple levels and perching structures to avoid collisions, falling from perches, and resulting bone fractures (Hartcher and Jones 2017). 

In an enriched cage, the requirement for dust bathing is usually addressed by providing feed on a plastic mat, which is soon exhausted (Hartcher and Jones 2017). Additionally, dominant hens can deny access to more submissive hens. An aviary and free-range systems with provided litter material allow for dust bathing behavior, but management must ensure that the material is kept dry and lose and maintain the outdoor areas accordingly. 

Cage-free aviaries and free-range systems come with new challenges. The large groups of hens in an aviary system can increase antagonistic behavior like feather pecking. This behavior has been shown to originate from individual birds and can spread more easily through larger groups (Hartcher and Jones 2017). The enrichment of the diet by natural foraging can lead to nutrient imbalances which in turn can exacerbate feather pecking. Mortality due to predation is higher in outdoor systems and not all hens use the outdoor facilities (Knierim et al. 2006). Furthermore, a higher prevalence of red mites (Dermanysses gallinae) was found in outdoor housing systems, which can increase stress and lead to more antagonistic behavior (Sosnówka-Czajka et al. 2021). This must be alleviated by proper management.  

Broiler chickens are normally reared indoors on the floor and free-range systems are not so widespread. Additionally, slower-growing breeds are often used for free-range and organic systems, making it more difficult to compare the behavior of the birds in different housing systems. In fast-growing broilers, it was observed that the birds did not make much use of extra space due to the weight-related walking impairment at a certain age (Weeks et al. 1994), though at the beginning, the chickens were more active in free-range systems (Weeks et al. 1994, Zupan et al. 2005). Slower-growing breeds were observed to readily use additional space and enrichment objects like perches up to the end of the production cycle, but similar issues concerning range use as in layers were found (Kanstrup et al. 2021). Another study concluded that slow-growing breeds are more suitable for free-range systems based on better welfare parameters. However, no significant differences for the housing systems were found (Abdourhamane and Petek 2022). 

Finally, alternative housing systems can increase welfare and the opportunity for laying hens to show their natural behavior, but more maintenance and biosecurity measures are needed to achieve this on a long-term basis and minimize losses while maximizing production. In broiler chickens, slow-growing breeds should be used in free-range systems. Fast-growing breeds are restricted in their use of the enriched environment due to their anatomy.


In conclusion, while alternative housing systems has perceived benefit for chicken welfare through expression of natural behaviour one must also not neglect the potential detrimental effects it poses to chickens. Perhaps it would be favourable to utilize breeds (e.g., dual purpose breeds) that are adapted to the outdoor/free-range production system. For broiler production, slow-growing breeds should be used in free-range systems. Fast-growing breeds are restricted in their use of the enriched environment due to their impaired ability to move. Moreover,innovative strategies are needed to achieve better welfare on a long-term basis and minimize losses while maximizing production. Regardless of the housing system, maintaining a strict biosecurity system is the key to address food safety concerns. 


Abdourhamane, İbrahima Mahamane, and Metin Petek. 2022. ‘Health-Based Welfare Indicators and Fear Reaction of Slower Growing Broiler Compared to Faster Growing Broiler Housed in Free Range and Conventional Deep Litter Housing Systems’, Journal of Applied Animal Welfare Science: 1-12. 

Castellini, C., Mugnai, C., Moscati, L., Mattioli, S., Amato, M. G., Mancinelli, A. C., & Dal Bosco, A. (2016). Adaptation to organic rearing system of eight different chicken genotypes: behaviour, welfare and performance. http://Dx.Doi.Org/10.1080/1828051X.2015.1131893, 15(1), 37–46.

De Vylder, J., Dewulf, J., Van Hoorebeke, S., Pasmans, F., Haesebrouck, F., Ducatelle, R., & Van Immerseel, F. (2011). Horizontal transmission of Salmonella Enteritidis in groups of experimentally infected laying hens housed in different housing systems. Poultry Science, 90(7), 1391-1396. 

DONALDSON, C.J. and O’CONNELL, N.E. (2012) The influence of access to aerial perches on fearfulness, social behaviour and production parameters in free-range laying hens. Applied Animal Behaviour Science 142: 51-60.  

European Food Safety Authority, & European Centre for Disease Prevention and Control. (2022). The European Union One Health 2021 Zoonoses Report. EFSA Journal, 20(12), e07666. 

Fraser, D. (2008). “Understanding Animal Welfare.” Acta Veterinaria Scandinavica 50.  doi:10.1186/1751-0147-50-S1-S1. 

HARTCHER, K., & JONES, B. (2017). The welfare of layer hens in cage and cage-free housing systems.

World’s Poultry Science Journal, 73(4), 767-782. doi:10.1017/S0043933917000812  

Heuer, O. E., Pedersen, K., Andersen, J. S., & Madsen, M. (2001). Prevalence and antimicrobial susceptibility of thermophilic Campylobacter in organic and conventional broiler flocks. Letters in Applied Microbiology, 33(4), 269–274. 

Holt, P. S. (2021). Centennial Review: A revisiting of hen welfare and egg safety consequences of mandatory outdoor access for organic egg production. Poultry Science, 100(12), 101436.

Iannetti, L., Neri, D., Santarelli, G. A., Cotturone, G., Vulpiani, M. P., Salini, R., … & Messori, S. (2020).

Animal welfare and microbiological safety of poultry meat: Impact of different at-farm animal welfare levels on at-slaughterhouse Campylobacter and Salmonella contamination. Food Control, 109, 106921.

Ijaz A, Veldhuizen EJA, Broere F, Rutten VPMG, Jansen CA. The Interplay between Salmonella and Intestinal Innate Immune Cells in Chickens. Pathogens. 2021 Nov 19;10(11):1512. doi: 10.3390/pathogens10111512. PMID: 34832668; PMCID: PMC8618210. 

Kanstrup, M., Singh, L., Göransson, K. E., Widoff, J., Taylor, R. S., Gamble, B., … & Holmes, E. A.

(2021). Reducing intrusive memories after trauma via a brief cognitive task intervention in the hospital emergency department: an exploratory pilot randomised controlled trial. Translational psychiatry, 11(1), 30. 

Knierim, U. Animal welfare aspects of outdoor runs for laying hens: a review. NJAS – Wageningen

Journal of Life Sciences, Volume 54, Issue 2, 2006, Pages 133-145. 

Lücke, F. K. (2017). Microbiological safety of organic and conventional foods. In Foodbalt 2017, 11th Baltic Conference on Food Science and Technology “Food science and technology in a changing world”, April 27-28, 2017, Jelgava, Latvia, conference proceedings, ISSN : 2255-9817.

McMullin, P. (2022). Infectious diseases in free-range compared to conventional poultry production. Avian Pathology, 51(5), 424-434. 

Methner, U., R. Diller, R. Reiche, and K. Bohland. 2006. ‘Occurence of salmonellae in laying hens in different housing systems and conclusion for the control’, Berliner Und Munchener Tierarztliche Wochenschrift, 119: 467-73. 

Nenadović, K., Vučinić, M., Turubatović, R., Beckei, Z., Gerić, T., & Ilić, T. (2022). The effect of different housing systems on the welfare and the parasitological conditions of laying hens. Journal of the Hellenic Veterinary Medical Society, 73(3), 4493–4504. 

Novoa Rama, E., Bailey, M., Jones, D. R., Gast, R. K., Anderson, K., Brar, J., Taylor, R., Oliver, H. F., & Singh, M. (2018). Prevalence, Persistence, and Antimicrobial Resistance of Campylobacter spp. from Eggs and Laying Hens Housed in Five Commercial Housing Systems. Foodborne pathogens and disease, 15(8), 506–516. 

Permin, A., & Ranvig, H. (2001). Genetic resistance to Ascaridia galli infections in chickens. Veterinary Parasitology, 102(1-2), 101-111. 

Pettersson, IC, Weeks, CA, Wilson, LRM & Nicol, CJ. (2016). Consumer perceptions of free-range laying hen welfare, British Food Journal, vol. 118, no. 8, pp. 1999-2013. 

Rodenburg, T., Van Krimpen, M., De Jong, I., De Haas, E., Kops, M., Riedstra, B., . . . Nicol, C. (2013).

The prevention and control of feather pecking in laying hens: Identifying the underlying principles. World’s Poultry Science Journal, 69(2), 361-374. doi:10.1017/S0043933913000354 

Rosenquist, H., Boysen, L., Krogh, A. L., Jensen, A. N., & Nauta, M. (2013). Campylobacter contamination and the relative risk of illness from organic broiler meat in comparison with conventional broiler meat. International Journal of Food Microbiology, 162(3), 226–230. 

Sharma, N., Hunt, P. W., Hine, B. C., McNally, J., Sharma, N. K., Iqbal, Z., … & Ruhnke, I. (2018). Effect of an artificial Ascaridia galli infection on egg production, immune response, and liver lipid reserve of free-range laying hens. Poultry science, 97(2), 494-502. 

Sherwin, C. M., Nasr, M. A. F., Gale, E., Petek, M., Stafford, K., Turp, M., & Coles, G. C. (2013).

Prevalence of nematode infection and faecal egg counts in free-range laying hens: relations to housing and husbandry. British Poultry Science, 54(1), 12–23. 

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(1), 31–42. 

Sosnówka-Czajka,E.,Skomorucha,I. & Herbut,E.(2021).The Welfare Status of Hens in Different Housing Systems – A Review. Annals of Animal Science,21(4) 1235-1255. 

Sosnowski, M., & Osek, J. (2021). Microbiological Safety of Food of Animal Origin from Organic Farms. Journal of Veterinary Research, 65(1), 87–92. 

Wageha A. Awad, Claudia Hess & Michael Hess (2018) Re-thinking the chicken–Campylobacter jejuni interaction: a review, Avian Pathology, 47:4, 352-363,

DOI: 10.1080/03079457.2018.1475724 

Weeks, C. A., Nicol, C. J., Sherwin, C. M., & Kestin, S. C. (1994). Comparison of the behaviour of broiler chickens in indoor and free-range environments. Animal Welfare, 3(3), 179-192. 

Widowski, T., Classen, H., Newberry, r., Petrik, m., Schwean-Lardner, K., Cottee, Yan, F.F., Hester, P.Y. and Cheng, h.w. (2014) The effect of perch access during pullet rearing and egg laying on physiological measures of stress in White Leghorns at 71 weeks of age. Poultry Science 93: 1318-1326. 

Zupan, M., Berk, J., Wolf-Reuter, M., & Stuhec, I. (2005). Broiler behaviour in three different housing systems. Landbauforschung Volkenrode, 55(2), 91-9