Behavior and body temperature alterations in piglets anesthetized for castration during a four-hour recovery phase

Abstract

One way to eliminate pain during surgical castration is to provide general anesthesia by intramuscular injection. However, its disadvantage is the long recovery phase, during which anesthetized piglets have to be separated from the sow and managed appropriately. In this study, rectal temperatures, respiration rate, soiling and behavior changes were monitored in 119 piglets for 4 h after the intramuscularly administration of a ketamine-azaperone-mixture for general anesthesia and castration. The study aimed to identify the least distressing form of separation. For this, different types of separation containers, farm equipment and heat sources were used in 3 individual trials during separation of piglets. Over the course of the recovery period, body temperatures and behaviors of piglets underwent significant alterations. The temperature span was largest after 2 h in all trials (35.0–42.6 °C). Rectal temperatures were influenced by the kind of separation, heat provision, and age: Piglets separated in boxes were warmer than piglets separated in crate corners (P = 0.0016). Non-warmed piglets had lower temperatures than fully (P < 0.0001) warmed piglets. Additionally, rectal temperatures of 4-days old piglets were lower than those of 5-days old ones after 2 h (P < 0.0001). Piglets were more soiled after 4 h when they were not warmed compared to piglets in containers fully warmed (P < 0.0001). The kind of container also had an effect on soiling, as scores were higher after 2 h for piglets kept in buckets than those in perforated boxes (P = 0.0522). Warmed piglets breathed more frequently than non-warmed piglets (P = 0.0039). The behaviors pedaling and lying were more prominent in the first 2 h of the recovery period, while moving forward and head bumping occurred more often in the later half. The behavior slipping was only observed in buckets. It was concluded that the recovery phase is a stressful experience, especially for very young piglets. This means that piglets need to be taken care of appropriately to ensure that animal welfare is not reduced past a general anesthesia, which was originally applied to increase welfare during a painful intervention. Anesthetized piglets need to be warmed and possibly dried during the recovery phase to avoid life-threatening cooling.