Productive and welfare parameters in trimmed laying hens: A systematic review-meta-analysis

The objective of this study was to evaluate the effects of beak trimming-using a hot blade or infrared radiation-on mortality, egg production, feather pecking, and corticosterone levels in laying hens, using systematic review-meta-analysis (SR-MA) methodology. A total of 1775 citations were identified. The number of birds evaluated was 76 for corticosterone, 6172 for mortality, and 5460 for egg production. Twenty-three articles were assessed, with 13 included in the quantitative synthesis. Birds subjected to hot blade trimming showed a lower probability of mortality (Relative Risk - RR = 0.47; p = 0.087) compared to untrimmed birds, with high heterogeneity (I² = 94.64 %). Both shallow (≤ 5 mm; RR = 0.64; p < 0.0001) and deep (> 5 mm; RR = 0.02; p < 0.0001) beak trimming reduced mortality compared to untrimmed birds. No consistent evidence was found linking beak trimming to changes in egg production or corticosterone levels; however, due to the low number of studies and methodological variability, these findings should be interpreted with caution. Infrared beak trimming appears to be a promising, less invasive alternative, showing potential welfare benefits without compromising performance. Further standardized research is needed to strengthen conclusions, especially on stress-related physiological responses.