A non-invasive technique for measuring the electroencephalogram of broiler chickens in a fast way: the 'chicken EEG clamp' (CHEC)

A device was developed to measure in a fast way the electroencephalogram (EEG) of broiler chickens in a non-invasive way. The 'chicken EEG clamp' (CHEC) consists of a framework with two pointed electrodes, fitting as a clamp around the chicken's head. The EEG is recorded by the two active electrodes firmly contacting the skin overlying over the midst of the brain. The device is equipped with a pre-amplifier and is grounded. Validation of the CHEC was done in three groups of broilers: 1. chickens anaesthetised with ketamine-xylazine, 2. chickens anaesthetised with carbon dioxide in oxygen and 3. chickens locally anaesthetised with lidocaine applied under the skin of the brain. It appeared that the EEG can be obtained almost immediately, after 5 to 10 seconds recordings are available. The EEG traces obtained with the CHEC device were considered as reliable for two reasons: EEG patterns of the three groups are different from each other, while the EEG characteristics of the groups are representative for the anaesthetic used. Even clear EEG spindling, a typical EEG pattern in wake chickens, could be seen in the locally anaesthetised animals. The experiment proved that reliable, external, non-invasive EEG recordings of broilers can be obtained in a fast way, allowing quick assessment of the EEG in large numbers of animals.