This study explores the welfare implications of different castration methods in dogs, with particular attention to pain and stress. Although castration is widely performed, understanding how different techniques influence welfare outcomes remains important, particularly in relation to the pain experienced by the animal. The research compares surgical and chemical castration, using facial grimace scoring to evaluate pain associated with each approach.
Focus of the Study
Twelve adult male dogs were randomly allocated into two equal groups (n = 6 per group). One group underwent surgical castration (orchiectomy), while the second group received chemical castration through intratesticular injection of 70% glycerol.
Pain was assessed using a facial grimace scale adapted for dogs, which scoring specific facial action units including orbital tightening, ear tension, mouth tension, and head position. Assessments were conducted at baseline, in the hours immediately following the procedure, daily during early recovery and then weekly.
Statistical analysis was used to evaluate changes over time and differences between the two groups.
Key Findings
The study revealed clear differences in both the intensity and duration of pain between the two methods:
Surgical castration was associated with more intense short-term pain. indicators appeared rapidly within the first few hours, with facial expressions such as eye tightening and ear tension peaking early. however, these signs largely resolved within one to three weeks.
In contrast, chemical castration resulted in milder but more prolonged discomfort. Pain developed more gradually, typically peaking between 48 hours and one week, with signs persisting for up to six weeks.
Overall, the findings suggest distinct pain profiles: surgical castration produced sharper, short-lived pain, whereas chemical castration led to lower-level but longer-lasting discomfort. Facial expressions proved to be consistent and effective indicators of pain across both methods.
What this means?
These findings highlight that the welfare impact of castration is not straightforward, but instead reflects a trade-off between the intensity and duration of pain. While surgical castration resulted in more acute discomfort, chemical castration was associated with prolonged, albeit milder, pain.
This reinforces the importance of considering not only how severe pain is, but also how long it persists when evaluating animal welfare. A procedure that appears less invasive may still result in extended discomfort, with potential implications for recovery, behaviour, and overall wellbeing.
From a practical perspective, the results emphasise the need for effective pain management strategies for both methods, as well as continued monitoring beyond the immediate post-procedural period.
Limitations
Several limitations should be considered when interpreting these findings. The sample size was small (n = 12), which may limit generalisability.
Pain assessment relied primarily on facial grimace scoring. While this is a validated and widely used method, it may not fully capture the complexity of pain when used in isolation. Incorporating additional behavioural or physiological measures could provide a more comprehensive assessment.
The study also focused on short- to medium-term outcomes and did not explore longer-term effects or individual variability. Further research is therefore needed across larger populations and varied clinical settings.
Conclusion
Overall, this study highlights important differences in how pain is experienced following surgical and chemical castration in dogs. Surgical castration was associated with more intense but short-lived discomfort, whereas chemical castration resulted in milder yet more prolonged pain responses.
Rather than identifying a single superior method, the findings suggest that each approach presents distinct welfare considerations that must be carefully balanced. As interest in less invasive procedures continues to grow, this research underscores the importance of comprehensive pain assessment and management, regardless of the method used.
Take-Home Message
Different castration methods may not eliminate pain, but instead change how it is experienced, short and intense, or milder but prolonged. In either case, effective pain management remains essential to safeguarding animal welfare.
