I show an A. M. D. Howard as a private in Co. "H" of this unit. The initials would appear to match. Where did you find information about his service? (That might help determine if this is your ancestor, or not.)

However, I also show the same name as follows:

Howard, A.M.D., AL 25th Infantry, Co. "G"
Howard, A.M.D., AL 7th Cavalry, Co. "H"
Howard, A.M.D., AL 8th (Livingston's) Cavalry, Co. "B"
Howard, A.M.D., AL Cavalry, Hardie's Battalion, Reserves, Co. "A"

Are these the same man transferring from one unit to another? I have no way of determining that.