I tried feeding liquid Valerian to my Tb when I moved her (years ago).
I can't remember the brand, but it was a black and yellow label.
Unfortunately, it didn't seem to have any effect on my horse, but did turn my WPs against me. They refused to add it to her feed, claiming it smelled of rotting cabbage.
S
My friend recently used it on her cob who was a total stress head when travelling, the change was amazing and now she get out and about without any hassle.