Canadian Poultry Magazine

Features Welfare
Layers and the welfare trade-off

Assessing the health impacts of housing changes for hens.


April 8, 2020
By Mike Petrik

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If the manure is too dry, the barn becomes dusty like the one depicted here. This also increases disease challenge and impairs immunity.

Canada has recently adopted a new Code of Practice for Laying Hens, developed by the National Farm Animal Care Council. This code was developed with input from the poultry industry, government, veterinarians, animal welfare scientists and the humane societies. It will phase out conventional and require layers to be housed in more extensive systems – either furnished cages or cage-free.

This change is in response to shifting cultural demands for animal care. The general public is uncomfortable with intensive livestock housing and a greater emphasis is being placed on the emotional and mental well being of animals used for food.

Egg producers have always been very responsive to the desires of consumers. For decades, the public demanded abundant, inexpensive, safe eggs, produced efficiently from healthy hens. Conventional cages were ideal for this. The quality, safety and relative price of eggs have all improved greatly over the past 50 years, all while decreasing the industry’s carbon footprint.

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The industry is now facing challenges because of our successes. The public is now demanding more freedom and comfort for the hens, but the improvements we have made are assumed to be established. The improvement in animal welfare is an “and”, not an “or”. The public will not accept a decrease in food safety, a noticeable increase in relative price or an increase in resource usage to offset the welfare gains.

An interesting example came in Europe, where pasture access is widely encouraged or even demanded. When avian influenza was spreading through Europe and the disease was seen as a human threat, one of the first edicts was to require birds to be housed indoors or at least under a roof to protect the public health.

There is no doubt that opportunities to perch, dust bathe, interact socially and perform other natural behaviours is a benefit to bird welfare and can be provided to a much greater extent by the housing systems we are moving to. Unfortunately, it is also true that more extensive housing puts birds at greater risk of developing disease and incurring injuries.

Equipment manufacturers have improved the design of the housing systems to mitigate these problems. That said, management must still play a crucial role in the success of a flock to stay healthy.

Increased disease risk occurs in more extensive housing due to increased exposure to manure, decreased air quality, increased group size and complexity of the environment. Compared to conventional cages, non-cage housing increases the risk of disease the most. Furnished cages are a compromise between the two systems.

Exposure to manure
Increased access to manure results in exposure to pathogens, including bacteria, viruses and parasites that had previously been well controlled in conventional cages. Diseases that had not been seen in decades are beginning to become a threat again. Worms, E. coli, Salmonella, Blackhead and coccidiosis are all of greater concern in flocks that have increased access to litter.

Management of the pullets is an important aspect of disease control in these higher challenge housing systems. Training pullets to use the perches and access the system, and effective vaccination and rearing are necessary for the flock to thrive.

Litter management in the lay house is crucial. If the litter is too wet, the populations of many of the pathogens will explode, increasing disease risk and producing ammonia. If the manure is too dry, the barn becomes dusty, which also increases disease challenge and impairs immunity.

Decreased air quality
Air quality is very closely linked to manure management. High ammonia levels from too much humidity in the barn causes chemical damage to the respiratory system and decreases the ability of cilia to clear out pathogens that get into the system. This increases the risk of airsacculitis from E. coli, respiratory viruses such as infectious laryngotracheitis, infectious bronchitis and mycoplasma. It also chemically irritates the eyes, in extreme situations causing irritation or even blindness.

Dusty conditions resulting from excessively low humidity irritate the respiratory tract and act as a carrier to allow bacteria and viruses to penetrate deep into the bird’s system. There is a delicate balance that farmers must find to maintain healthy air quality while keeping temperatures in a comfortable range.

Increased group size
Increased group size exacerbates the problems that occur when groups of chickens interact. Pecking orders are extremely rigid and inter-bird aggression can be high in big groups. Cannibalism can occur if birds begin competing over any resource. This can be the result of restricted food access, insufficient attractive perches, competition over preferred nests or any other resource they can compete over.

The social nature of birds to mimic each other can result in smothering issues. In European surveys, smothering often results in a significant proportion of the flock mortality, ranging from five to 50 per cent of the mortality in a flock and three to five per cent of the birds placed. Smothering can occur from either hens congregating together in an act of viral curiosity or from panic caused by the flightiness of a neighbor. Farmers can use even lighting, air movement and distractions to help combat these destructive behaviors.

Complex environment
Complexity of the environment required in the code includes the provision of perches, nests and foraging areas. Chickens strongly desire perches, with over 90 per cent perching at night if given the opportunity. However, perches that are poorly designed, poorly maintained or dirty can cause bumblefoot, a serious, painful infection of the foot that is very difficult to treat.

Perches are also linked to keel bone fractures. Perch placement can make it difficult for flying birds to land safely, also increasing the risk of injuries.

Nest areas and scratch areas can allow manure to accumulate in both non-cage and furnished cage systems, increasing the risk of disease as above, and may also be seen as desirable areas to be. This can incite birds to accumulate, pile and smother if management strategies are not able to change the birds’ behavior.

The housing changes that are required in the new NFACC code of practice result in improved bird welfare through behavioural and mental freedom. However, they increase the risk of health problems for the birds. Equipment design and management strategies are able to mitigate and minimize these risks, but farmers need to remain aware of the risks and vigilant.


Mike Petrik is director of technical services at McKinley Hatchery Inc.


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