If you can, I would suggest that the (adorable by the way) filly be given Ulcergard or Gastrogard FOR the trip. Can you get it to the seller and had them give it prior to shipping and then each day during the trip if more than one day? I would keep her on that for awhile once she arrives too, and play it by ear depending on how stressed she seems. For a weanling, probably 3-4 "ticks" on the dosing syringe will be enough for a daily dose (same for both GG and Ulcergard) so one big horse "dose" will last awhile. Alfalfa of some type would be another idea. I always ask for (and get) enough of the current feed so they can be transferred over to any new feed gradually.