Identifying horses is a necessary part of horse ownership. But whether we should mark horses with a microchip implant or a hot iron brand has become a subject of "heated" debate.

Austrian researcher Christine Aurich, DVM, PhD, professor at the Graf Lehndorff Institute at the University of Veterinary Sciences in Vienna, and a research team set out to find a resolution to this issue. They studied the amount of stress brought on by iron branding and microchip implantation in 14 young foals between 1 and 5 months old–seven were branded and seven were microchipped–and compared the results.

By measuring the foals’ heart rates, physical reactions, salivary levels of cortisol (the "stress" hormone), and skin temperatures, Aurich’s team found no significant difference in stress levels between the horses that received an iron brand on the thigh or a microchip injected into the neck.

"We were a little bit surprised that branding did not result in a stronger stress reaction," Aurich said. "There was a tendency towards a higher cortisol release in the foals after branding, but it did not reach statistical significance