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Do better cages or cage-free environments really improve the lives of hens?

Research suggests that moving hens from battery cages to cage-free environments reduces the time animals spend in pain substantially.

There are around 8.3 billion egg-laying hens worldwide, around the same number as humans.

Most of these hens live in cages that give them less space than an A4 sheet of paper.

It often has no nest to lay its eggs in; no room to rest; and its movement is almost entirely restricted. It can’t carry out its normal behaviors of foraging, pecking, or dustbathing, so hens will often peck themselves or one another, leading to skin wounds and their feathers being plucked out. In many countries, chickens are ‘de-beaked’ – where their beak is partially removed – to stop this.

Hens are bred to be highly productive. Hens will often lay around 300 eggs per year. That’s very different from the wild ancestor of modern chickens – the red junglefowl – which lays around a dozen per year. And much higher than in 1900, when commercial hens would lay around 80 eggs yearly. The productive period of hens only lasts 12 to 18 months; they’re then killed to make space for younger hens that can produce eggs at a higher rate. Male chicks – of no use to the intensive egg industry – are often culled in macerators shortly after birth.

This is the harsh reality for billions of hens living in factory farms today. Objections to this practice are growing, and in some parts of the world, policies are changing.

In the graphic below, I’ve shown the size of a standard battery cage per hen and compared the amount of space needed to do basic behaviors such as standing, turning, preening, and wing-flapping. As you can see, battery cages are too small for hens to perform any of these behaviors.

Series of boxes showing the size of a battery cage, compared to the area needed for hens to do basic behaviours.

In response to animal welfare concerns, some countries have banned battery cages. The European Union banned them in 2012.1

Producers have since moved to ‘enriched cages’. These require laying hens to have at least 750 cm² of space each. That’s not much bigger than an A4 sheet of paper, which is 624 cm². And as you can see in the chart above, the space is largely insufficient to perform basic behaviors such as tidying feathers and wing flapping. These regulations mandate that all hens “have a nest, perching space, litter to allow pecking and scratching, and unrestricted access to a feed trough and drinking device”.

The EU now plans to ban the use of any cage by 2027. Many hens would therefore move to ‘cage-free aviary’ or free-range systems. These systems are not necessarily the same: most free-range certifications require hens to access outdoor areas. This is often not the case in cage-free aviaries; they are mostly indoors.

How much difference will this make to the welfare of chickens? Are enriched cages much better than battery cages, and will ‘cage-free aviaries’ provide them with a pain-free life?

In this article, I look at the research and data on the estimated pain levels of hens in different production systems.

Hens in cages spend most of their life in pain; cage-free systems reduce this significantly

It’s extremely hard to quantify pain levels in other animals. Doing this among humans is difficult enough since pain is subjective and can be experienced differently among individuals.

To quantify pain in other animals, researchers can draw on various disciplines, including evolutionary biology, neuroscience, and pharmacology. Researchers Wladimir J. Alonso and Cynthia Schuck-Paim have written a detailed book on the analytical framework that is used to assess pain and discomfort felt by egg-laying hens [it’s available for free].2

The research organization Welfare Footprint built on this work to present the number of hours of pain endured by hens in three production systems:

It evaluated the amount of time that the average hen spent in various levels of pain across its laying life.3 Here, the lifespan of hens in the different systems was assumed to be the same: 60 to 80 weeks before being slaughtered (with the first 20 weeks being a pre-laying phase, followed by 40 to 60 weeks of laying).4

It’s not just the total hours of pain that matters. The intensity is just as – if not more – important. Many of us would rather spend 5 hours in mild pain than 1 hour in intense pain.

This pain can be physical or psychological and is broken down into four levels of pain (from most to least intense):

In the chart, we can see the number of days spent at different intensities across the systems, as estimated by Schuck-Palm and Alonso. Estimates represent the total time in pain endured by the average hen due to each of the different harms and deprivations experienced. The researchers only considered the 16 hours per day that hens were awake. So when converting hours to days, I have divided by 16 rather than 24. That means the number of waking days in pain is shown.

There is almost no difference in the time spent in excruciating pain between the systems. Hens endured this on average for around 3 minutes in all of them. As we’ll see in the next section, the cause of this extreme pain was either fractures during transport or diseases that evolved into sepsis (generalized infection), such as acute peritonitis or a vent wound.5

But there is a large reduction in the amount of disabling, hurtful, and annoying pain within cage-free hens compared to caged ones. Disabling pain was reduced by 63%, hurtful by 57%, and annoying pain by 70%.

So, it’s not just that cage-free hens spend less time experiencing minor annoyances. They see significant reductions in disabling and pervasive levels of pain.

Moving a battery-caged hen to a furnished one will also make a significant difference in the time spent in disabling pain. But the reduction in hurtful and annoying pain is much less.

What causes pain in egg-laying hens?

In the chart below, we see the contributors to each level of pain for each production system.

Some of the largest contributors to pain in caged – particularly battery cage – systems is the lack of basic necessities such as a nest, roosting spot (where they rest and sleep), or space to forage. This is one of the biggest differences between caged and cage-free environments.

Keel bone fractures are another key source of pain. The bones of industrial egg-laying hens are much weaker and more brittle. One of the main explanations for this is that the intensity of egg-laying – where hens lay one almost daily for over a year – requires calcium. This calcium is thought to be partly taken from the hen’s skeleton, which makes it more fragile.6 This makes them very susceptible to fractures.

Surprisingly, it has been suggested that it’s hens in cage-free environments that are at the greatest risk of keel bone fractures, although there are recent studies that contest this.7 If fracture risk is higher in cage-free hens, it may be because they have more space to move and fly, making them more likely to collide with obstacles, leading to injuries. In caged environments, hens have much less space to move, and the likelihood of high-speed collisions is much lower.

That is a key point from this analysis: while the conditions for hens in cage-free settings are better than in caged ones, they still experience significant pain and discomfort because they are still bred and raised to be highly productive. This rate of egg production has significant costs for their health and welfare.

Breakdown of the causes of pain in egg-laying hens between different production systems. Source: Welfare Footprint.
Stacked bar chart of the causes of pain in different egg-laying systems.

Going cage-free has massive welfare benefits, but going egg-free is obviously the best way to reduce suffering

It is a good thing for animal welfare for the EU to ban all caged environments over the next five years.

As we’ve seen, moving to cage-free aviaries reduces suffering significantly. Multiply this by the number of hens in the world – 8.3 billion – and we can see how large the welfare benefits would be if all countries did the same.

But going cage-free does not put an end to this suffering. These hens will still spend more than a third of the year in pain or discomfort, often because of the pressures of producing eggs so intensively.

This is clear from the research.8 Few studies attempt to quantify pain in the way that Schuck-Paim and Alonso do, but there are others that evaluate the advantages and disadvantages of different production systems. Cage-free systems improve welfare by allowing hens to perform natural and basic behaviors that they wouldn’t be able to – such as perching, flapping, and moving freely. But they may be at higher risk of fractures.9 The welfare of hens in these systems can also be more variable and depends on the experience of the farmer to set up their environments appropriately.

Finally, there have been a number of studies that suggest that mortality rates are higher in cage-free settings. Now, mortality rates are not necessarily the most direct measure of levels of pain – since most of a hen’s suffering will occur during its laying life – but it’s still an important metric to consider. Hens might have higher mortality rates in cage-free settings due to collisions with objects; more aggressive pecking or social behavior; or exposure to manure or infections. A large meta-analysis on this question found that the experience or maturity of the cage-free setting was important: mortality rates can be higher for inexperienced producers.10 But mortality rates fall over time as producers build knowledge. And in experienced systems, mortality rates are not higher than in cages.

Overall, the research suggests strong welfare benefits in moving from caged to cage-free environments. As a consumer, you can reduce animal suffering by opting for cage-free eggs. But better still, you can reduce or eliminate them from your diet entirely.


I would like to thank Cynthia Schuck-Paim, Max Roser, and Pablo Rosado for their valuable comments and suggestions on this article.


  1. The Directive to ban battery cages was agreed in 1999 but did not outlaw them until 2012.

  2. The authors stress that this is an evolving area of research with existing knowledge gaps and uncertainty around various input parameters.

  3. It’s extremely difficult to quantify this individually since specific hens could have different experiences, injuries, and pain tolerances. So this metric is typically employed at the population level and then given as the average for an individual. As an example, if a hen that has a keel fracture experiences 10 hours of pain, and 70% of the population experiences a keel fracture, then the average pain noted is 7 hours per hen. That doesn’t mean every hen will experience 7 hours of pain; some will experience more, and some not at all.

  4. In reality, the lifespan of caged hens might be higher. In some countries (outside Europe, where the practice is banned), producers try to extend the productive life of hens using a practice called ‘induced molting’, where feed is typically withdrawn for several days. This practice is much more common in caged than cage-free settings. This might mean the total hours of suffering for a caged hen are even greater than the results below show. Schuck-Paim, C., Negro-Calduch, E., & Alonso, W. J. (2021). Laying hen mortality in different indoor housing systems: a meta-analysis of data from commercial farms in 16 countries. Scientific Reports, 11(1), 3052.

  5. Egg yolk peritonitis is where a yolk is formed, but the full egg is not. This means the yolk is ‘laid’ internally within the hen’s abdomen. It forms a swollen and painful abdomen, often leading to breathing problems. This can develop into sepsis, a likely painful condition, and ultimately prove fatal.

  6. There are various other potential explanations for why hens are so susceptible to fractures. One is that their bone density is highly correlated with the age at which they first lay eggs (i.e., their ‘puberty age’). If hens lay eggs too early – which is often the case for industrial ones – then their bones are unlikely to have formed properly.

    This paper by Toscano et al. (2020) discussed these explanations in detail.

    Toscano, M. J., Dunn, I. C., Christensen, J. P., Petow, S., Kittelsen, K., & Ulrich, R. (2020). Explanations for keel bone fractures in laying hens: are there explanations in addition to elevated egg production? Poultry science, 99(9), 4183-4194.

  7. Rufener, C., & Makagon, M. M. (2020). Keel bone fractures in laying hens: a systematic review of prevalence across age, housing systems, and strains. Journal of Animal Science, 98(Supplement_1), S36-S51.

  8. Appleby, M. C., & Hughes, B. O. (1991). Welfare of laying hens in cages and alternative systems: environmental, physical and behavioural aspects. World's Poultry Science Journal, 47(2), 109-128.

  9. Hartcher, K. M., & Jones, B. (2017). The welfare of layer hens in cage and cage-free housing systems. World's Poultry Science Journal, 73(4), 767-782.

  10. Schuck-Paim, C., Negro-Calduch, E. & Alonso, W.J. Laying hen mortality in different indoor housing systems: a meta-analysis of data from commercial farms in 16 countries. Sci Rep 11, 3052 (2021).

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    author = {Hannah Ritchie},
    title = {Do better cages or cage-free environments really improve the lives of hens?},
    journal = {Our World in Data},
    year = {2023},
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