Electroencephalographic studies of adult cattle associated with electrical stunning, throat cutting and carcass electro-immobilization

Twelve adult cattle were electrically stunned head-only (400 V, 2.5 A, 50 Hz) behind the ears for four seconds. Within ten seconds of stun initiation, the carotid arteries, jugular veins, trachea and oesophagus were severed. Twenty seconds after the stun initiation, ten animals received an electro-immobilization current (80 V peak, 14.3 Hz, 5 ms square wave, 300 mA) nose to anus for periods ranging from 30-37 seconds. Electroencephalographic (EEG) traces were recorded before and after the stun up until electroimmobilization and at cessation of electro-immobilization by means of implanted electrodes, and animal movement was recorded on videotape. Before the stun, the EEG trace was within a window of sensibility (10-40 microV amplitude). During the stun, the amplitude increased and sometimes exceeded 500 microV. At the end of electro-immobilization, EEG amplitude was less than 10 microV, indicating insensibility. This amplitude was reached in the two non-immobilized animals 57 seconds and 63 seconds after stun initiation. During stunning, the forelegs and hindlegs usually tucked under the animals. Various degrees of foreleg extension then occurred. From about ten seconds post-stun, paddling movements occurred, at which time the EEG trace showed large-amplitude waves characteristic of a stunned animal. During immobilization, the animals stiffened and breathing stopped. After immobilization weak muscle spasms occurred that did not interfere with dressing operations. Non-immobilized animals moved excessively, inhibiting dressing. It is concluded that adult cattle rendered insensible by stunning do not recover sensibility during the stun/throat-cut/immobilization operation and therefore this procedure is humane.