Vertebral artery contribution to cerebral cortex perfusion in cattle after slaughter by ventral neck incision: a systematic review.

Abstract

BACKGROUND: Jewish shechita and Islamic halal are distinct yet similar forms of slaughter by exsanguination via ventral neck incision (SEVNI); neither permits preslaughter stunning. SEVNI has been criticized on the grounds that the vertebral arteries in cattle, which remain intact after SEVNI, may continue to supply blood to the brain, potentially delaying loss of consciousness (LOC) and causing unnecessary pain and distress to the animal. In this context, LOC is the loss of cortical awareness, which by definition abolishes sensibility and pain perception. The objective of this review is to evaluate the literature that specifically addresses the role of the vertebral artery in brain perfusion following SEVNI. METHODS: This study was not funded. A non-registered systematic search of PubMed, Google Scholar, the Cochrane Library, Medline, and Web of Science (last searched 02/10/2026) identified experimental, observational and physiological studies that assessed vertebral artery hemodynamics and/or evaluated the functional significance of the vertebral artery in cattle. Non-cattle studies, studies lacking relevant measures, reviews, commentaries, and abstracts without full text were excluded. Quantitative pooling (meta-analysis) was not performed due to methodological and outcome variability therefore results were synthesized narratively. RESULTS: Thirteen studies were included, with all articles independently reviewed by co-authors to minimize risk of bias. Using the ROBINS-I framework, the overall risk of bias across included studies was assessed as moderate. Across the reviewed studies, evidence consistently demonstrated that immediately following SEVNI, vertebral blood flow and pressure decrease to negligible levels, with most residual flow diverted away from the cerebral cortex. LIMITATIONS: Study limitations include heterogeneous study designs, variable outcomes and methods. CONCLUSION: The available evidence indicates that vertebral artery flow following SEVNI is unlikely to be sufficient to sustain cortical perfusion, support integrated cortical function or delay LOC.