There are few things as beautiful and graceful as a horse in motion. Expressing that motion in a photograph can be a little tricky. You can choose to pan along with the motion, blurring the background behind the animal. Sometimes the motion will be apparent, especially with an animal like a horse that has a flowing mane. Another though less used option is to allow some motion blur in the subject. Many modern viewers will not appreciate an image in which the subject is blurred. But I think it can add a feeling of great energy and motion. Take a look through this series of images and decide for yourself.