Investigating the short- and long-term impacts of pain from surgical castration on affective states in piglets

Abstract

Abstract Surgical castration of male piglets is a routine procedure performed to improve meat quality. Pain due to castration can last for up to 4 days, negatively impacting animal welfare. The objective of this study was to assess the impact of surgical castration and practical pain alleviation methods during and after castration on piglets’ short and long-term affective states and activity. Piglets were surgically castrated (n = 22), castrated with analgesics (n = 21), or sham-handled (n = 22) at 3 days of age. Data on piglets’ activity, tails, and grimaces were collected for 1, 6, and 24 hours after castration treatments. An attention bias test was performed in week 1 (n = 31) and 12 (n = 33) to assess anxiety (an affective state), with feed (positive stimulus) and loud bangs and flashing lights (negative stimuli) presented simultaneously. Latency to eat, behavioral responses, and activity were recorded during the test. Castration treatment and sampling timepoint impacted activity levels hours after treatments. Piglets’ behavior and activity at week 1 suggest a negative impact of surgical castration on anxiety. Impacts of castration treatments observed in week 1 were no longer detected in week 12. Results confirm that surgical castration negatively impacts affective states of 1-week-old piglets, but results did not support a long-term impact detectable at 12 weeks of age. As this is the first study assessing the relationship between painful procedures and piglet affective state, more research is needed to better understand the impacts on these and other measures of pig affect.