As you go past the stall belonging to the mare who had been acting strange when you arrived you realized that the stall door had been left open. You were about to call the attendant to tell her the door was open, but you figured there wouldn't be any harm in shutting it yourself.
When you moved in front of the stall however the white mare was turned away from you as she ate some oats. She swished her tail to the side which gave you occasional views of her vaginal lips behind it. A smell hit your nose as your ears started to itch followed by the rest of your body as you breathed the mare's scent in deeply.
You didn't recognize the mare's scent right away, but after a moment you realized that the smell was of her heat. You felt your arousal start to grow and looked down at your pants to see that its tented with an erection. The mare's tail was pushed to the side now as you got a good look at the mare's vagina as she turned back and looked at you and let out a scared whinny.
You didn't care about the mare's behavior as you pulled off your clothes and the itch started to spread over your body down to your feet as you moved in closer and breathed in deeply. You stood there named and didn't care who might see you right now, all that was going through your mind was the idea of mounting and breeding this mare.
As you looked down at your penis you were surprised to see it so massive but you didn't care. For a moment you thought you something in the hay beneath you.