cage-free farms. This problem is greatly aggravated by the ban on traditional treatment options in Europe, North Ameri- ca and many other countries, due to human health concerns. In the absence of treatment, flock mortality can be very high. The frequency with which certain bacterial infections occur, namely colibacillosis, erysipelas and pasteurellosis, is also greater in cage-free systems.
Behaviour and welfare Feather pecking (FP) is a major welfare issue in laying hens. In its severest form, characterised by feather removal, FP can result in denuded body areas, often followed by pecking of the skin, wounding, bleeding and, in extreme cases, mortality due to cannibalism. Pecking around the cloaca (vent pecking), another type of injurious pecking, can also be a critical cause of internal infections, cannibalism and mortality in layer flocks. Injurious pecking is a learned behaviour passed on from one chicken to another and is very difficult to control once an outbreak starts. Although it can occur in any housing system, this behavioural problem can spread more easily and become even more serious in cage-free flocks – given the larger group size, there are more birds to learn the behaviour or to fall victim to it. Accordingly, several surveys have reported that a high percentage of cage-free flocks suffer from FP (40-80%). Similarly, the reported percentage of cage-free flocks affected by cannibalism is also substantial (up to 40%). Apart from the larger group size, other specificities of cage- free housing may contribute to the greater magnitude of in- jurious pecking (severe FP and vent pecking) on these farms. Free-range flocks are exposed to outdoor light which is much more intense than indoor light, even on a cloudy day – higher light intensities increase the risk of injurious pecking. Am- monia levels are usually greater in cage-free sheds; elevated
levels of ammonia have been linked to the onset of FP. Infes- tation by worms has also been associated with the triggering of injurious pecking. Apart from the associated pain and stress, there is another crucial welfare aspect of severe FP: feather loss. Without proper feathering, the skin is at greater risk of injury and birds lose insulation from draughts and cold weather. In addition, damage to the tail and flight feathers of the wings affects flying ability which, in turn, may increase the risk of bone fractures in cage-free layers.
Skeletal health Several authors have reported that bone strength is higher in cage-free than in caged hens. Paradoxically, the prevalence of keel bone fractures (KBF) is greater in cage-free layer flocks. Accordingly, KBF is a particular welfare concern in cage-free farms. It has even been suggested that this might be the most critical welfare issue currently faced by the egg produc- tion industry. Although the exact causes for its development have not been fully identified, it has been proposed that housing and equipment features may contribute to KBF.
Attention to details Although laying hens housed in cage-free systems can move more freely and better express their natural behaviour, some factors can turn their welfare into a challenge. Air quality, foot health, higher mortality rate, feather pecking and keel bone fractures are therefore important welfare concerns in cage-free egg production that need to be addressed by egg producers.
For more information log on to
alltech.com/en-gb/ cage-free-layer-production.
▶ POULTRY WORLD | No. 10, 2021 17
On average, hen mortality rate is greater in cage-free systems, espe- cially free-range, compared to furnished cages.
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