title: Avian reflex and electroencephalogram responses in different states of consciousness.
abstract: Defining states of clinical consciousness in animals is important in veterinary anaesthesia and in studies of euthanasia and welfare assessment at slaughter. The aim of this study was to validate readily observable reflex responses in relation to different conscious states, as confirmed by EEG analysis, in two species of birds under laboratory conditions (35-week-old layer hens (n=12) and 11-week-old turkeys (n=10)). We evaluated clinical reflexes and characterised electroencephalograph (EEG) activity (as a measure of brain function) using spectral analyses in four different clinical states of consciousness: conscious (fully awake), semi-conscious (sedated), unconscious-optimal (general anaesthesia), unconscious-sub optimal (deep hypnotic state), as well as assessment immediately following euthanasia. Jaw or neck muscle tone was the most reliable reflex measure distinguishing between conscious and unconscious states. Pupillary reflex was consistently observed until respiratory arrest. Nictitating membrane reflex persisted for a short time (<1 min) after respiratory arrest and brain death (isoelectric EEG). The results confirm that the nictitating membrane reflex is a conservative measure of death in poultry. Using spectral analyses of the EEG waveforms it was possible to readily distinguish between the different states of clinical consciousness. In all cases, when birds progressed from a conscious to unconscious state; total spectral power (PTOT) significantly increased, whereas median (F50) and spectral edge (F95) frequencies significantly decreased. This study demonstrates that EEG analysis can differentiate between clinical states (and loss of brain function at death) in birds and provides a unique integration of reflex responses and EEG activity.
authors.affiliation: Animal and Veterinary Science Research Group, Scotland's Rural College (SRUC), West Mains Road, Edinburgh EH16 4SA, UK.
authors.forename: Dale A
authors.initials: DA
authors.lastname: Sandercock
authors.affiliation: School of Veterinary Medicine, University of Glasgow, UK.
authors.forename: Adam
authors.initials: A
authors.lastname: Auckburally
authors.affiliation: School of Veterinary Medicine, University of Glasgow, UK.
authors.forename: Derek
authors.initials: D
authors.lastname: Flaherty
authors.affiliation: Avian Science Research Centre, Scotland's Rural College, Auchincruive Ayr KA6 5HW, UK.
authors.forename: Victoria
authors.initials: V
authors.lastname: Sandilands
authors.affiliation: Institute for Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary & Life Sciences, University of Glasgow, UK. Electronic address: Dorothy.McKeegan@glasgow.ac.uk.
authors.forename: Dorothy E F
authors.initials: DE
authors.lastname: McKeegan
mesh_terms: D000818:Animals; D001921:Brain / Q000187:drug effects; D058256:Brain Waves / Q000187:drug effects / Q000502:physiology*; D002227:Carbazoles / Q000494:pharmacology; D002645:Chickens / Q000502:physiology*; D003243:Consciousness / Q000187:drug effects / Q000502:physiology*; D004562:Electrocardiography; D004569:Electroencephalography; D005260:Female; D005583:Fourier Analysis; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006993:Hypnotics and Sedatives / Q000494:pharmacology; D010812:Physical Stimulation; D012018:Reflex / Q000502:physiology*; D013045:Species Specificity; D014422:Turkeys / Q000502:physiology*; D014473:Unconscious, Psychology
chemical_list: D002227:Carbazoles; D006993:Hypnotics and Sedatives; C007005:carprofen
keywords: Anaesthesia; Avian; Consciousness; Cranial reflexes; EEG; FFT power analysis