"Aggressive behavior in horses is expensive," said Michelle A. Kennedy, DVM, a private practitioner in Delta, Colo. Veterinary expense, property damage, loss of use of affected horses, and the emotional cost associated with the death of an animal if injured severely during an aggressive act all demand a reliable way to change this behavior in the horse. Kennedy has experienced success in using an equine electronic collar with a number of horses.

"Aggressive behavior in horses results in a range of injuries that often must be attended to by a veterinarian, from minor cuts and bruises to career-ending or life-threatening injuries," she added. "These injuries are a direct result of being bitten or kicked, or chased through or over a fence."

She noted that every equine practitioner is going to see horses that have experienced these injuries, and all too often, the veterinarian will be asked how it can be prevented in the future. If no possible medical cause is detected (for example, a gelding with undetected retained testicular tissue that causes stallion-like behavior or a mare with a hormone imbalance), the next step is determining how to stop the undesirable behavior.

Isolating the horse can work in some cases if the owner has the space to do this, said Kennedy. However, some horses are emboldened by a barrier since they know the target horse will be less likely to show retribution since a fence is in the way. Not every horse owner is blessed with dead space between fence lines, and many boarding stables aren't able to accommodate a horse requiring isolation