Okay you are going to think I’m nuts but vics vapor rub. Put a tiny bit in his nostril the day before you leave home and a tiny bit each morning and he should have no problem. Learned this from an old timer, also helps when riding a stallion with mares he doesn know. Everything smells/tastes the same its all linked to smell. Works when putting medicated feed in their food also. Try it , its an easy solution and not harmful in any way.