Quantitative electroencephalography as a tool for evaluating pain-related neurophysiologic responses in cattle: a systematic review

Background: Electroencephalographic (EEG) methods have been employed to evaluate pain-related neurophysiologic responses during slaughter of cattle and have contributed to scientific discussions informing slaughterhouse regulations. The interpretation of EEG changes as pain remains controversial. This systematic review critically evaluates the literature on EEG used to infer pain during slaughter and other forms of noxious stimuli. Methods: A systematic review was conducted in accordance with Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines. PubMed/MEDLINE, Web of Science, Scopus, and Google Scholar were searched. Included studies evaluated EEG responses to slaughter or other forms of noxious stimuli in cattle. Risk of bias was assessed using ROBINS-I. Results: 9 studies met inclusion criteria. Electroencephalographic changes following ventral neck incision and other noxious stimuli were characterized by transient increases in high-frequency activity and shifts in spectral indices (F50, F95, Ptot). The risk of bias across studies was judged to be moderate. Clinical Relevance: Current evidence suggests that electrophysiologic changes observed after ventral neck incision may reflect nociception, defined as neural signaling in response to a noxious stimulus, but do not establish conscious pain perception, which requires preserved consciousness and integrated cortical function. In the context of slaughter, the observed EEG changes likely reflect rapid hemodynamic and metabolic deterioration of cortical function. Findings are limited by methodological heterogeneity, reliance on surface EEG recordings, motion artifacts, small sample sizes, and inherent limitations of EEG in localizing deep pain-processing structures and indirect inference of pain from EEG activity.