One of my mares refused to eat mud guard at all. She would leave the supplement at the bottom of the food bowl.
We give her the feelgood 30 skin supplement for her mud rash, which I've found works much better anyway, and she eats it all up.
I've never used mud-x so can't comment on that one!
i feed mine the mud gard powder. Shes as picky as they come and she eats it - even at the max dose.
never tried the mudx so cant comment on that.
have to say her mud fever isnt half as bad as it was before I started to feed the mud gard.