When trailer training a horse the ideal situation would be to start them at a very young age so when they see a trailer it’s just a normal everyday event. Unfortunately not everyone has that luxury and usually gets a horse that has already had a bad experience with a trailer.
It usually means they have been forced into a trailer with an impatient owner or maybe tossed around during the drive and had to scramble to keep standing which made them fearful. There are some horses that just simply refuse to get in because they can. Whatever their past experience is, it doesn’t change the fact that they won’t get in.
