nutrition for young horses

[David & Vicki Wheeler <dwheeler@icx.net>]

Tom, do you have any specific nutritional recommendations for young horses?
 I have a 3 year old that I've started ponying 2-3 days per week.  We are
only up to 2-5 miles at a time, but added some hill work this weekend.
Does he need anything special?

I'm working under the presumption that adding only speed or distance, but
not both applies to ponying as well.

TIA
Vicki Wheeler
E TN