A molecular and biochemical reference approach for validation of vision systems that automatically record catching damage in broiler chickens at slaughter

Catching damage, defined as lesions occurring during catching and associated preslaughter handling of broiler chickens, represents a significant challenge for animal welfare and carcass quality. Automated vision systems are increasingly implemented in slaughterhouses to detect carcass lesions; however, their validation is still largely based on macroscopic appearance or inspectors’ subjective visual evaluations. Visual assessment, either human or camera‑based, alone does not allow reliable determination of when a lesion occurred, making it difficult to distinguish between lesions arising during rearing or during catching, crating, transport or processing. Determining the age of lesions is essential both for accurate animal welfare evaluation and for production chain participants. The aim of this study was to develop a molecular and biochemical reference methodology that allows further training of the vision system to correctly recognize the age of lesions detected at slaughter. The approach was based on the established principle that mechanical injury induces a temporally ordered local response (inflammation), including activation of pro‑inflammatory pathways, subsequent recruitment of immune cells, and later extracellular matrix remodelling and tissue repair. In parallel, injured tissue undergo progressive oxidative and enzymatic degradation, generating colour changes that reflect the stage of tissue response. Together, these processes are expected to produce measurable, time‑dependent molecular and biochemical signatures in injured tissue. Sampling was conducted in a commercial slaughterhouse equipped with an automatic vision‑based detection system (ChickenCheck software, CLK GmbH). Tissue was collected from carcasses classified by the system as presenting catching damage lesions. Gene expression profiling is applied to quantify transcripts of early inflammatory cytokines (e.g., L1β, Il6, Tnf‑α), intermediate chemokines (e.g., CXCL8, CCL2), and late remodeling/fibrosis markers (e.g., MmP9, Tgfb1) using RT‑qPCR. In parallel, biochemical analyses are conducted to determine hemoglobin‑related parameters by UV‑Vis spectrophotometry and concentrations of heme degradation products (biliverdin, bilirubin and conjugates) using HPLC or LC‑MS/MS. Integrated statistical modelling, including mixed‑effects and multivariate analyses is used to derive biologically based lesion‑age categories. Analyses are expected to identify distinct molecular and biochemical patterns corresponding to different stages of catching damage lesions. Final laboratory analyses are currently underway and full results are expected prior to the conference presentation. This interdisciplinary approach links poultry welfare science, molecular pathology, and processing technology. It supports standardization of catching damage lesions assessment and contributes to the development of objective tools for welfare monitoring and quality control in the poultry industry.