Anaesthesia of pigs with CO2 : grouping is best

The study consisted in an evaluation of the welfare of pigs before and during anaesthesia with CO2. The results in terms of heart rate suggested that stress was highest when the pigs were being led to anaesthesia and during the first 40 s spent in the cage. Thereafter, weaker heart beats suggested the pigs were unconscious. As regards behaviour, the anaesthesia acted in several phases during which the animals' reactions were fairly characteristic. Recoil movements, and the inhalation and excitation phase suggested a stressful or even painful situation for the pigs.Subsequent postural collapse and convulsions are signs of loss of consciousness. Thus during anaesthesia with CO2, the period of inhalation of gas, together with that of excitation, are problematic for animal welfare.