I own a young endurance horse who just qualified on 80 kms.
Recently, he suddenly could not stand when i tightened the girth and ground the teeth after work.
My vet told me many endurance horse suffer from stomach discomfort and advised me to give him Twydil® stomacare.
After two weeks of this supplementation, he was in better condition already, did not grind the teeth anymore.
After one month he accepted the girth again and had recovered his weight.