Evaluation of the anaesthetic depth during piglet castration under an automated isoflurane-anaesthesia at farm level.

Piglet castration under isoflurane-anaesthesia could represent an alternative to the practice of castration without anaesthesia. The objective of this study was to evaluate practicality and effectiveness of an automated isoflurane-anaesthesia for castration. A field study on three different farms in Germany (farm A, B: 200 sows; C: 540 sows) was performed. In total, 1429 (1166 anaesthetised and 263 conventionally castrated) male piglets (age: 1-8 days; bodyweight: 0.7-3.7 kg) were monitored. All piglets were treated with nonsteroidal anti-inflammatory drugs directly before castration. Castration and anaesthesia were performed by the farm-manager in presence of a veterinarian. All farmers used the PIGNAP Pro® (Agrosystems GmbH, CH) anaesthetic device (5 vol.% isoflurane, 30% oxygen; flow rate: 2 l/min). Vocalisation and defensive movements of 1166 anaesthetised piglets was rated using a scoring system. Presence or absence of the palpebral- and flexor-reflex was noted. Approximately every second piglet was weighed and oxygen-saturation and pulse- frequency of 231 animals were measured during treatment. Rectal temperatures before and after castration of 264 anaesthetised and 263 conventionally castrated piglets were compared. Only 77% of the anaesthetised piglets showed a sufficient anaesthetic depth based on the assessment of reflexes as well as vocalisations and defensive movements. It was found that the probability for a sufficient depth of anaesthesia decreases with increasing age and weight. The measurements of the pulse-frequency and oxygen-saturation showed an average oxygen-saturation of 98% and an average heart rate of 270/min during anaesthesia. The conventionally castrated piglets had significantly higher rectal temperatures in comparison to the anaesthetised (p < 0.0001). The result of 77% sufficiently anaesthetised piglets is not adequate for commercial application of this technology.