Amber's eyes widened as she saw the stallion's fully erect penis.  It was huge.  "Oh gods," she murmured.  "I can't believe this."  She pushed herself to her feet, vaguely realizing that her inner thighs were still soaked from her powerful orgasm.  She stepped up next to the horse and stroked his muzzle gently.  "Sorry, boy," she murmured softly.  "You must not have had a mare for a long time, but I can't really help you with that.  It just wouldn't be right."