Body temperature changes in piglets anesthetized for castration during the recovery phase

Abstract In several countries, an application of general anesthesia for pain prevention during castration is discussed. A disadvantage is the prolonged recovery phase, accompanied by severe body temperature drops in piglets. Aim of this study was to investigate effects on body temperature during recovery after anesthesia. Piglets were anesthetized, castrated and placed in boxes (0.24m2) for 4h. Before, 2 and 4h after the application (0.3ml ketamine+azaperone/kg BW), rectal temperatures (RT) and skin temperatures behind the ear (ST) were measured. In a first trial, impacts of infrared lamp (250W, 50-55cm height) and number of animals per box (3 vs 6) were analyzed (n = 30). In a complementary trial, infrared lamps’ height (60 vs 70cm) and piglet age were varied (n = 27) and temperatures measured half-hourly. Differences were estimated in linear models (SAS® 9.4). Mean RT before anesthesia was 39.1±0.4°C with ranges of less than 1.9°C. After 2h, mean RT in lamp-warmed piglets increased to 40.8°C (P < 0.01), whereas in absence of lamps RT dropped to 37.3 (P < 0.001), with significant differences between groups (P < 0.001). To prevent life-threatening cooling, piglets with RT as minimal as 33.5°C were warmed immediately, so that their mean RT after 4h was not different from initial temperatures. Animal number per box caused no differences. Variation between individual RT was up to 8.2°C at 2h (first trial). Means in the second trial did not differ, but variation pattern of individual temperatures was highest after 1h (6.1°C), indicating that individual differences regarding anesthetics or external factors might occur. When lamps hung lower ST were higher after 3h (P < 0.05) and 4h (P < 0.01). RT and ST were dependent on age after 0.5h (P < 0,05, respectively) and tendentious at 1h and 2h, indicating that older piglets can rely on more distinct temperature regulation abilities and use endogenous energy resources to regain homeostasis.