If you have a ranch how many horse total can you have?
Depends. (: You don't get set amounts of extra horse slots just by buying the ranch.
When you buy a ranch, your horse slots don't change. However, you can build barns on your ranch to increase your horse-holding capacity by 1, 3, 5, or 8 slots (depending on the size of the barn). With a huge ranch full of platinum barns, along with the Esroh Pitchfork bonus and the Horse Collectors club bonus, I believe you can have 248 slots (assuming I did the math right).