Electrophysiologic evidence of loss of consciousness in cattle during slaughter with and without stunning: a systematic review and methodological overview

Background: Slaughter without prior stunning as practiced under Jewish and Islamic religious law raises certain particular animal welfare issues, notably the time between the incision and loss of consciousness (LOC). LOC marks the point at which cortical processing required for perception, including pain, is no longer possible. Quantifying time to LOC in animals is challenging. To date, the most direct and potentially objective means of doing so is the use of electrophysiologic methods. These are the focus of this paper. Methods: This paper includes a concise discussion of electrophysiology as applied to slaughter, addressing a critical gap in foundational electrophysiologic knowledge required to interpret LOC and insensibility in the veterinary literature. Then, using a PRISMA-guided systematic approach, this review synthesizes neurophysiologic evidence on time to LOC in cattle. A review was conducted using PubMed/MEDLINE, Web of Science, Cochrane Library, and Google Scholar (through December 2025). Experimental cattle studies using EEG, ECoG, or evoked potentials were included, while non-bovine, behavioral-only, or methodologically insufficient studies were excluded. Nine studies were included, and risk of bias was assessed using ROBINS-I. Results: Overall risk of bias across included studies was judged to be moderate. Studies using electrocorticography (ECoG) reported electrophysiologic markers consistent with LOC occurring between 4.4 and 13 seconds after incision, with mean values ranging from 7.5 to 10.8 seconds. Reported times vary across studies, particularly those using scalp EEG, likely due to methodological differences and limitations. Conclusions: The highest-quality available electrophysiologic data, suggests that LOC occurs rapidly following slaughter without stunning.