Take this with a grain of salt, as I'm no expert....
I think the designation of "horse" comes after a colt turns 5. Of course, a colt still has his plumbing, as does a "horse".
Much like a female retains the "filly" designation up until she's 5, once she is 5 then she is designated as a "Mare".
So, an ungelded male is designated a "colt" at 2, 3, 4, then a "horse" at 5 and up.
A gelding is always a gelding, no matter the age.
Then again, I could be wrong...
