Find the “mutant donkey woman” horse

The advantage on buying a horse is that you will be able to call that -kind- of horse back even when it dies. Thus, if you buy a nice horse such the Kentucky Saddler, American Standardbred or Hungarian Half-bred you won't need to break them again to use them.

By the way, once you buy a horse it won't automatically come to you .. you must open your inventory and use the item you bought representing the horse... then, the horse you were using will go away and the 'item' horse will come to you. This item representing the horse has unlimited uses.

Unfortunately it doesn't count. You MUST play the story missions with the SAME horse. In the other hand, you must do this with STORY only missions. If by some mean you end the game you will have to start it again to get this trophy. (Replaying story missions doesn't count). This makes this trophy the only one you can miss.

By the way, there are a total of 57 story missions.