Hi Donna,
Sounds like your horse's feet are tender. At that age, I wouldn't try
to push him over hard ground much either. His bones are probably not
going to take the abuse. Bones take a year and sometimes two years to
fully strengthen when they're stressed. A moderate amount of hard going
at that age will do a world of good for his bone development, but use
caution. Listen to what your horse is telling you. You're setting a
foundation for a lifetime of riding here, not a "flash in the pan". A
good, fast walk or slow trot for seven to ten miles three times a week
in the hills is good training for a young horse just starting his
career. Practice obstacles when the urge for speed clouds your
thinking. (That's what I had to do.) Do a couple of moderate limited
distance rides later this year too. You'll meet other riders with the
same goals and maybe find a training partner in the bunch!
His feet will toughen as you continue to ride those surfaces. Just
keep the speed down. I also had a horse with really tender feet and we
pulled his shoes for six weeks or so and rode him at a slower speed to
toughen the soles. Painting the soles with iodine after our rides
probably helped also.
My current horse will always shorten up crossing pavement for traction
reasons. He doesn't slip that way. Good Luck!, Nikki