Evaluation of the inhalation anaesthesia for the surgical castration of piglets

n order to evaluate the acceptability of inhalation anaesthesia with Isoflurane as anaesthetic in Switzerland, anaesthetic machines for inhalation anaesthesia produced by two companies were tested according to a procedure elaborated previously. The evaluation of the quality of anaesthesia was based on field studies on 6 farms. A total of 338 piglets were castrated under anaesthesia. During the study, the behaviour of the piglets was observed in order to evaluate animal welfare and assessed according to a scoring. For assessing the requirements for of occupational health and safety, measures of isoflurane in the ambient air of the housing were carried out on four farms.
During positioning in the tray and at the beginning of the anaesthesia induction with the appliance of company 1 which lasted for 84 seconds, most of the animals exhibited strong defence movements. This was less pronounced for the appliance of company 2. During castration both appliances reached a good quality of anaesthesia for more 90% of the animals (i.e. scoring level of 1 or 2). On the average, 74 % of all piglets were classified as scoring level 1 (optimal anaesthesia), 18 % as scoring level >1 to 2, 4 % as scoring level >2 to <3, 3 % as scoring level >3 to <4 and 1 % as scoring level 4 (anaesthesia clearly insufficient), respectively, for the appliance of company 1. The appliance of company 2 showed similar values. The recovery phase was gentle and exempt from excitations in most cases. The animals were able to walk after 3.5 minutes on average. Since the used anaesthetic isoflurane does not have an effect on postoperative pain an additional application of an analgesic is necessary. The machines complied with the requirements of occupational health and safety.
In Switzerland, a practicable anaesthetic machine for inhalation anaesthesia during castration of piglets is available. The evaluation of this machine under conditions of practice showed that the inhalation anaesthesia if performed cautiously and combined with an injection against postoperative pain results in a sufficient pain relief for this purpose.