Evaluation of pain and inflammation associated with hot iron branding and microchip transponder injection in horses.

The research article compares the pain and inflammatory effects of hot iron branding and microchip transponder injection in horses. The study found that hot iron branding caused significantly greater pain and subsequent inflammation in horses than microchip injection.

Research Methodology

• The study employed a randomized controlled clinical crossover design with seven adult horses.
• Four observers scored the horses’ behavioral reactions to hot iron branding and microchip transponder injections, which were indicators of pain levels.
• Physiological and biochemical responses were used to assess and compare local and systemic inflammation, including a condition of increased pain sensitivity called allodynia.
• Serum cortisol concentration, which indicates stress levels, was measured repeatedly during the first 24-hour period of the study.
• Sham treatments (procedures mimicking the actual treatments but without their therapeutic effect) were conducted one day before and seven days after treatments to evaluate the horses’ memory of the unpleasant experience.

Research Findings

• Hot iron branding elicited a significantly stronger behavioral reaction indicative of pain compared to microchip transponder injection. The odds ratio (OR), which represents the odds that an event will occur in one group compared to the odds of it occurring in another group, was 12.83.
• Allodynia, measured using skin sensitivity testing, was significantly greater after hot iron branding than after microchip transponder injection, with an odds ratio of 2.59.
• However, neither hot iron branding nor microchip injection produced signs of spontaneously occurring pain during the remainder of the study period, nor did they cause an increase in serum cortisol concentrations, indicating that neither procedure stressed the horses significantly.
• Hot iron branding areas showed a significant increase in skin temperature and swelling, with an odds ratio of 14.6.
• No systemic inflammation was detected after any of the treatments based on measurements of serum amyloid A concentration, a common test for inflammation.

Conclusions

• The results showed that microchip transponder injection caused less pain and did not pose a higher long-term risk compared to hot iron branding. It induced fewer signs of pain and inflammation.
• The study concluded that hot iron branding, a traditional method of identifying horses, inflicts more pain and should be eliminated where possible.