Cannibalism in poultry

Cannibalism in poultry is the act of one individual of a species consuming all or part of another individual of the same species as food. It commonly occurs in flocks of domestic hens reared for egg production, although it can also occur in domestic turkeys, pheasants and other poultry species. Cannibalism can occur as a consequence of feather pecking which has caused denuded areas and bleeding on a bird's skin. Cannibalism can cause large mortality rates within the flock and large decreases in production due to the stress it causes. Vent pecking, sometimes called 'cloacal cannibalism', is considered to be a separate form of cannibalistic pecking as this occurs in well-feathered birds and only the cloaca is targeted.

Poultry species which exhibit cannibalism are omnivores. For example, hens in the wild often scratch at the soil to search for seeds, insects and even larger animals such as lizards or young mice, although they are mainly herbivorous in adulthood. Feather pecking is often the initial cause of an injury which then attracts the cannibalistic pecking of other birds – perhaps as re-directed foraging or feeding behaviour. In the close confines of modern farming systems, the increased pecking attention is easily observed by multiple birds which join in the attack, and often the escape attempts of the cannibalised bird attract more pecking attention.

Chicks brooded with a hen had lower mortality levels due to feather pecking and cannibalism compared to non-brooded chicks. This may indicate the hen guides the chicks to peck at more rewarding substrates, such as food or litter.

Cannibalism among layer hen flocks is highly variable; when it is not problematic, mortalities among production systems are generally similar. Published data on the prevalence of cannibalism could be misleading due to the inclusion of vent-pecking by some researchers but not others. Mortalities, due mainly to cannibalism, can be up to 15% in egg-laying flocks housed in aviaries, straw yards, and free-range systems. Because egg-laying strains of chickens can be kept in smaller group sizes in cage systems, cannibalism is reduced, leading to a lowered trend in mortality as compared to non-cage systems. In a study which examined 'skin damage' (most of which would have been cause by pecking) on hens at the end of their productive lives, damage was lowest in hens from free range systems, followed by barns, then furnished cages, and highest in conventional or battery cages.

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