Microchipping has been found to be less painful than hot-iron branding, a Danish study has revealed.

Hot-iron branding is more painful than inserting a microchip, a Danish study has found. It concluded hot-iron branding should be abandoned wherever possible.

The study, carried out at the University of Copenhagen, compared the behavioural and physiological responses of seven horses that were subjected to both hot-iron branding and microchip insertion.

Danish and European Union law requires horses to be individually identified.

Hot iron branding has been used for this purpose for many years. Microchip transponders have become available more recently.

In the study, published in the American Journal of Veterinary Research, Dr Casper Lindegaard and others aimed to assess the relative degree of pain caused by hot-iron branding and microchip insertion.

They set out to do this by assessing the horses' behavioural responses to each procedure. They also compared the degree of stress and the local and systemic inflammation that occurred.

Seven horses were observed undergoing microchip insertion and hot-iron branding under standardised conditions. The horses were also subjected to "sham treatments" in which the conditions were similar but no injection or branding occurred.

Each procedure was recorded on video and four observers independently assessed the horses' reactions. In addition, the scientists monitored the clinical condition of each horse for seven days after each treatment.

They found that the horses showed significantly more signs of aversive behaviour after hot-iron branding than they did after microchip injection.

Also, hot-iron branding caused significantly greater skin sensitivity around the treatment site compared with microchip injection. For 48 hours, there was significantly more heat and swelling of the skin where the hot-iron branding was carried out than there was at the site of the microchip injection.

Heart rate increased at the time of branding or injection, but returned to normal quickly after the microchip injection. It remained high for five minutes after hot iron branding.

Neither procedure produced an increase in serum cortisol.

The researchers conclude that hot-iron branding caused more pain than microchip injection. They recommended that hot-iron branding should be abandoned if possible.