An equine friendship can seem sweet, but if two horses become agitated whenever they're apart—a classic case of equine separation anxiety—it's time to implement a "cooling off" period by separating the pair for a couple of weeks so they regain their independence. Engineering a breakup can be challenging in any case, but it is best done cold turkey rather than gradually. Before you start, however, make sure you've laid the groundwork for a successful split.
1. Make sure the horses are in good health. Separating tightly bonded horses can be physically stressful for them. If either of the horses is ill, injured or otherwise compromised, that is only going to make the transition more difficult.
2. Eliminate other stressors. For example, if the duo has just moved to a new stable or pasture, give them a chance to settle into their new environment before separating them. Or, if your horse finds trailering so stressful that he bonds with his travel partner, take short, frequent trips to reduce his anxiety about it before making the split.
3. Improve your horse's ground manners. Brushing up on groundwork is always helpful and will fine-tune your horse's ability to focus on you---and not his other half---during separations. Take him to an area where he can still hear and see his pal, and work on leading, halting and backing. Later, add in more complicated tasks, such as walking over ground poles, to heighten his concentration. For the food-motivated horse, treats can be used sparingly to help command his attention.
For the separation process, it works best to take one of the horses to a different property for at least two weeks. If that isn't doable, set them up on opposite ends of your farm where they cannot see each other. Keep each in a safe and secure enclosure. Extreme cases require careful monitoring to make sure no one gets hurt---a few of these horses will run through fences without regard for their safety. But be warned: They will raise a racket. Resist the urge to end the drama by reuniting the buddies. As long as you have taken the appropriate steps, and your horses are still eating and drinking, they will eventually settle down and adjust to living more independently.