Inhalation anaesthesia for the castration of piglets: CO2 compared to halothane

General anaesthesia with 80 % CO2/20 % O-2 and 5 % halothane in O-2 (mask i nduction) was compared for castration of 3-week-old piglets. One group was castrated without anaesthesia. Of the noncastrated control groups one had C O2- and one halothane anaesthesia, one breathed room air through the induct ion system, and one was held in castration position. The behaviour to induc tion and castration was assessed, and the cortisol-, ACTH- and beta-endorph in plasma concentrations were determined to quantify the stress elicited by anaesthesia, castration and handling. Violent struggling and vocalization were elicited by CO2 and positioning into the mask induction system while b reathing room air; halothane induction was quiet. CO2 induced profound surg ical anaesthesia; whereas under halothane anaesthesia some animals exhibite d still a slight reaction to castration. Recovery was fast, smooth and quie t. Permanent violent struggling and vocalization were elicited by castratio n without anaesthesia. Plasma cortisol was not a sensitive tool to judge ca stration stress. The high ACTH and beta-endorphin plasma concentrations eli cited by CO2 anaesthesia confirm our clinical experience. General anaesthes ia is fast and safely induced with CO2 in piglets and castration can bit pe rformed without any reaction, but with CO2 anaesthesia the stress is not re duced.