Debeaking, also called beak trimming is the partial removal of the beak of poultry, especially chickens and turkeys. Most commonly, the beak is shortened permanently, although regrowth can occur. The trimmed lower beak is somewhat longer than the upper beak. USA's UEP guidelines suggest that in egg laying strains of chickens, the length of the upper beak distal from the nostrils which remains following trimming, should be 2 to 3 mm. The term “debeaking” implies that the entire beak is removed during the trimming process, though in reality only half or less of the beak is removed.

In some countries, such as the United States, beak trimming is common in egg-laying strains of chickens and turkeys as a preventive measure to reduce the incidence of cannibalism and improve livability. However, commercial broiler chickens are not routinely beak trimmed due to their docile nature. In some countries, beak trimming is done as a last resort where alternatives are considered not to be possible or appropriate.

In close confinement, cannibalism and aggression is common among turkeys, ducks, pheasants, quail, and egg laying strains of chickens of many breeds (including both heritage breeds and modern hybrids). The tendency to cannibalism varies among different strains of chickens, but does not manifest itself consistently. Some flocks of the same breed may be entirely free from cannibalism, while others, under the same management, may have a serious outbreak.

Mortalities mainly due 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 caged systems, cannibalism is reduced leading to a lowered trend in mortality as compared to non-cage systems. Cannibalism among flocks is highly variable and when it is not problematic, then mortalities among production systems are similar.