Pain in the hours following surgical and rubber ring castration in dairy calves: Evidence from conditioned place avoidance

Male cattle reared for beef are typically castrated. Male calves born on dairy farms are increasingly reared for beef, so a better understanding of how to humanely perform this procedure in dairy systems is now required. We studied the short-term affective responses of dairy calves to castration using a conditioned place aversion paradigm. Young Holstein bulls (16 d old, n = 30) were castrated by either rubber ring (n = 15) or surgery (n = 15), and then kept in a visually distinctive recovery pen for 6 h after the procedure. Calves acted as their own control and were sham castrated and allowed to recover for 6 h in another visually distinctive pen. During both castration and sham procedures, calves received a sedative (xylazine, 0.2 mg/kg), local anesthetic (lidocaine, 5 mL), and a nonsteroidal anti-inflammatory (meloxicam, 0.5 mg/kg). After exposure to both treatments (castration and sham), calves were tested for place aversion by providing free access to the 2 pens where they experienced the different treatments. Calves were tested for aversion 48, 72, and 96 h after their last treatment. We recorded how much time they spent in each pen and where they chose to rest. We did not find differences in time spent resting or resting location, suggesting that calves did not form a more negative memory of castration in comparison to the sham procedure. The lack of treatment effects may be due to features of our testing paradigm, including effective multimodal pain control during the 6-h conditioning period and limiting testing to the first days after the procedure.