For centuries, animal owners have sought ways to identify their foals, horses and other animals and differentiate them from those of neighbors. Identifying marks also helped in regaining animals that became lost or were stolen. Branding with a hot iron was often the method of marking an animal in a distinctive way.
Currently, for animal welfare reasons, many veterinarians promote implanting a microchip over the traditional practice of branding foals or young horses based on the thinking that implanting a microchip causes less pain and stress than using a branding iron.
Some officials of major sport horse breed registries deny that branding really causes pain or stress to foals.
A team of researchers lead by Christine Aurich at the University of Veterinary Medicine, Vienna has addressed the question of which is best for foals by examining the effects on foals of branding compared to use of microchips.
Previous work had suggested that branding was significantly more stressful than implanting a microchip but the studies were carried out in adult horses and no investigations had been undertaken in foals, although horses are generally marked as foals.
In collaboration with other scientists at the Vetmeduni Vienna, Regina Erber in Aurich's group therefore examined the levels of stress hormones in the saliva of foals when they were branded or when a microchip was implanted in their necks. She also monitored the behaviour, the body temperature and the heart rates of the foals while they were marked and afterwards (changes in heart beat are associated with stress).
The results showed that both methods were associated with similar acute levels of stress to the animals: cortisol concentrations in the saliva increased similarly and in each case there was a similar transient increase in heart rate and in aversive behaviour.
It appears that the immediate behavioural and physiological changes caused by both methods are extremely similar. Furthermore, they appear at least in part to be caused by handling and fixation of the foals and not by the actual marking procedures.
Not surprisingly, branding caused a skin burn that lasted for about a week. However, branding was also found to be accompanied by a generalized increase in skin temperature that lasted for several days. This is comparable to the response of humans to severe burn injuries. These changes were not found in foals that were not branded but instead marked by means of a microchip. The new results thus show that tissue damage caused by branding in foals is far more pronounced than expected.
Unlike adult horses, then, foals suffer very similar levels of stress immediately after they are branded or have a microchip implanted. However, branding induces more prolonged alterations in foals than implantation of a microchip.
As Aurich points out, "branding but not microchip implantation causes a necrotizing burn wound and a generalized increase in superficial body temperature, which together are indicative of significant tissue damage." Studies that focus solely on the acute stress response thus underestimate the effect of branding on the welfare of the animals.
The paper Physiological and behavioural responses of young horses to hot iron branding and microchip implantation by Regina Erber, Manuela Wulf, Mareike Becker-Birck, Susanne Kaps, Jörg Aurich, Erich Möstl and Christine Aurich has just been published online in The Veterinary Journal.
The work was carried out at the Graf Lehndorff Institute for Equine Science, a joint research unit of the University of Veterinary Medicine, Vienna, Austria, and the Brandenburg State Stud at Neustadt (Dosse), Germany.