Nerves, anxiety, excitement at being involved and traveling in a trailer, away from home, etc… all possible reasons. Some horses fret stoically while others just totally collapse mentally, some light up like a Christmas tree at the prospect of travelling/competing. Often, the result is loose poo. Maybe a shortlife calming supp prior to events is in order, or try taking him out more often to some easy trails, fun times.
Some love to compete, others hate to leave home… hard to say what your specific issue is. I have a fab trail buddy (Pheets : ) that is horrified of the trailer because he is so afraid that he will not come back to the same place. Been passed around TOO much and lives in a constant state of insecurity over it that I can’t quite eliminate completely. We are working on it… he gets pretty loose, too.
As for clean sox, I am not a fan of Show Sheen in any way (really dislike how the silicone only covers then dries out the fur SOOO fast!!) but it CAN help reduce/repel staining for show purposes. For daily maintenance, Wisk and water and/or a good stiff brush and elbow grease : ).
Sure there's right and wrong but mostly there's just a whole lotta different.