Effect of rate of induction of carbon dioxide anaesthesia on the time of onset of unconsciousness and convulsions.

The effect of different rates of induction of carbon dioxide anaesthesia on the time to loss of consciousness was investigated in broilers and hens. In experiment 1, 24 and 17 broilers, respectively, were exposed to 45 per cent carbon dioxide within 8 or 18 seconds (accession time). In experiment 2, 18 to 20 broilers and hens were exposed to either 35, 45, 55 or 65 per cent carbon dioxide within 8 seconds. The results indicated that, in general, the rate of accession is more critical than the final concentration of carbon dioxide; however, in 35 per cent carbon dioxide an exposure time of longer than 5 minutes is required to kill the birds. The time to sustained eye closure, time to onset of clonic and tonic convulsions and the duration of convulsive episodes were shorter in broilers than in hens. It is suggested that under commercial situations a final concentration of 55 per cent carbon dioxide would be suitable for killing broilers and hens.