Catch damage in broiler chickens: a systematic review of injury assessment methods and their limitations.

Catch damage in broiler chickens is widely used as an indicator of preslaughter welfare and carcass quality, yet its assessment methods vary considerably across the scientific literature. The objective of this review was to systematically evaluate how catch damage is defined, measured, and attributed in studies involving broiler chickens, with particular attention to methodological consistency and interpretational limitations. A structured literature search identified peer -reviewed studies addressing physical injuries associated with catching and preslaughter handling. Extracted information included injury definitions, assessment stage, scoring systems, sampling strategies, and approaches used to determine injury origin. The review revealed that catch damage is assessed using diverse and often non-comparable frameworks, including on-farm examinations, lairage inspections, postmortem slaughter line scoring, processing record analysis, automated image-based detection, and physiological or biochemical indicators. Catch damage definitions differed in anatomical scope, lesion size thresholds, counting rules, and aggregation level, while many studies relied on postmortem proxy measures such as bruising prevalence, fractures, condemnations, or dead-on-arrival (DOA) rates. These outcomes frequently represent cumulative trauma from multiple preslaughter stages rather than catching specific injury. Limited differentiation between recent and old injuries further constrains stage-specific attribution. Inconsistent reporting of observer training, reliability, and sampling design was also common. Collectively, these methodological differences contribute to measurement bias and restrict cross-study comparability, causal inference, and the development of evidence-based welfare interventions. Catch damage therefore not only represents a biological outcome, but also a measurement construct influenced by assessment context and protocol design. Greater harmonization of injury definitions, injury age classification, and standardized scoring procedures is needed to improve the reliability and practical applicability of catch damage severity as a welfare and quality indicator in broiler production.