Document type: scientific synthesis published in Animal Welfare
Authors: Kliphuis S, Tiemann I, Wever KE, Fijn L, Goerlich VC.
Abstract in French (translation): The effects of beak trimming on the behavior, morphology, and physiology of poultry: a systematic review
Despite scientific and ethical concerns, beak trimming(beak treatment or filing) remains a common practice in the poultry industry. Its purported effectiveness in reducing injuries and mortality related to pecking is the main reason for its widespread use. The objective of this systematic review was to identify the effects of beak trimming on the welfare of several species of poultry raised for commercial purposes (chickens [Gallus domesticus], turkeys [Meleagris gallopavo domesticus], ducks [Cairina moschata; Anas platyrhynchos], quail [Coturnix coturnix], guinea fowl [Numida meleagris], and pheasants [Phasanius cholchicus]). In accordance with strict inclusion and exclusion criteria defined a priori, 1,242 publications were screened for eligibility, resulting in the inclusion of 175 studies for data extraction. The risk of bias was assessed based on the information provided regarding key quality indicators. Due to the high heterogeneity of the 175 studies, a subset of 120 studies was analyzed based on welfare-related outcomes in the areas of behavior, morphology, physiology, and mortality, and presented as effect direction graphs showing the beneficial, harmful, or absent effects of beak size. Twenty-four studies focused on beak abnormalities; 71% of these reported morphological abnormalities, and 25% reported alterations in sensory abilities. Of 49 studies, mortality decreased in birds whose beaks had been trimmed in 51% of cases and increased in 8%, while 41% reported no measurable impact. Physiological indicators of stress did not show clear trends, but the procedure led to behavioral changes, such as a decrease in environmental pecking. The effects on feather preening and harmful pecking remain ambiguous. These results corroborate the inconsistent nature of the potential benefits of beak trimming and underscore the need to investigate the underlying causes of severe feather pecking and to refine techniques—not only in chickens.
Preview: Despite scientific and ethical concerns, beak trimming (beak treatment, or beak tipping) remains a routine procedure in the poultry sector. The perceived efficacy to reduce pecking-related injuries and mortality is the main reason for the common application of beak trimming. The aim of this systematic review was to identify the effects of beak trimming on the welfare of several commercially kept poultry species (chickens [Gallus domesticus], turkeys [Meleagris gallopavo domesticus], ducks [Cairina moschata; Anas platyrhynchos], quail [Coturnix coturnix], Guinea fowl [Numida meleagris] and pheasants [Phasanius cholchicus]). Following strict a priori in- and exclusion criteria, a total of 1,242 records were screened for eligibility, resulting in 175 studies included for data extraction. Risk of Bias was assessed based on the reporting of key quality indicators. Due to high heterogeneity of the 175 studies, a subset of 120 studies was analysed based on welfare-related outcomes in the domains of behaviour, morphology, physiology, and mortality and presented in effect-direction plots, showing beneficial, harmful or absent effects of beak trimming. Twenty-four studies investigated beak abnormalities, with 71% of those reporting morphological abnormalities and 25% altered sensory abilities. Of 49 studies, mortality decreased in trimmed birds in 51% and increased in 8%, while 41% reported no measurable impact. Physiological indicators of stress did not show clear patterns, but the procedure caused alterations in behaviour, such as a decrease in environmental pecking. The effects on preening and injurious pecking remain ambiguous. These results corroborate the inconsistent potential benefits of beak trimming and highlight the need for investigating underlying causes of severe feather pecking and refinement of techniques, not only in chickens.
