I love the idea and the long horizontal line-up is great. Would like to see more foreground as the image seems tightly cropped both top and bottom. Also, straightening the number banner would be beneficial.
excellent opportunity, but not quite there. the horizon is tilted without adding anything to the image. it's a bit dark (maybe try the shadow/highlights filter), and it is relatively soft. you might have gotten better dpc results had you focused in tightly on one or two of the horses as they came by you.
The motion is stopped ok. Image is interesting enough to look at, although I think your primary subject(s) are too distant to make a big impact on the voters. JMO. Good luck.