went out and feed this afternoon as usual. had put feed in one trough and turned to put feed in another one. noticed one mare at the first trough start to cough and act strange. i started toward her and she trotted away so i thought she was ok. but kept watching her for a while and realized she was sort of foaming at the mouth and heaving or trying to. caught her and tried to rub her throat to maybe help. nothing seemed to help so we called vet and he had us bring her in. he had to tube her and flush it out. we feed pellet feed which i thought was ok. vet said it was not uncommon for horses to choke on pellet feed. this was news to me. he suggested we mix something with the pellets. what would anyone advise? lucky mare seems to be ok. anyone else ever had this problem?