A minotaur typically begins a battle by charging at an opponent, lowering its head to bring its mighty horns into play. In addition to the normal benefits and hazards of a charge, this allows the beast to make a single gore attack with a +9 attack bonus that deals 4d6+6 points of damage.
the feat is another kettle of fish
If the melee attack you make at the end of a Charge hits, you do extra damage. If you have multiple attacks at the end of a Charge, the bonus damage only applies to one of them.
Size Bonus Damage
Medium +1d8
Large +2d6
Huge +3d6
Gargantuan +4d6
Colossal +6d6
There's a feat in the MiniHB and later in one of the Completes... With an upgrade somewhere later which I don't find right now... it gives +1d8 depending on size plus something to charges.