Hi, just saw your issue here…..It’s really pretty simple, as most young horses will do this and some high-energy ones will do even when mature. Just spray rope cross-ties with “Chew Stop” or Cayanne Pepper, or other stop chewing product. You can also get long, hard plastic tubes that cross-ties thread through so horses can’t damage ties. Some horses just have that energy and look for a passifier to entertain themselves when standing for time. Other horses are calmer or low energy and can fall asleep. Usually after a good work-out they are calmer and less likely to indulge in this behavior. Sometimes if cross-ties are high up and not too slack they find it more difficult to reach and quit trying.