Nice capture of this horse galloping! Love how you captured the tail and mane being blown back by the speed of the wind as this horse runs full gallop. An above average shot but there are a few points of improvement that would push this composition score higher. First, showing the horse's environment sometimes can compliment the subject but here it does not and there is too much. The main action is the horse at full gallop - show us more of that and less of the barn and hedge. Bringing us closer to the action will greatly increase the visual interest. The two ways to do this is to either zoom in closer to have your subject fill the frame as much as possible when capturing a fast moving object OR crop so that your main subject fills the frame. Crop out the top 1/4 of the photo to rid the composition of the barn that is not doing anything to compliment the photo. What you are then left with is a composition that is akin to a widescreen view that shows us the running horse and the space it runs in. You still might want to crop a tad from behind the horse and a tad in front of the horse to bring us even closer to the running horse. But be careful to not crop too much that you box the horse in! Leaving space before your moving object shows the viewer where your subject is moving to and gives the photo a feeling of open space for the action to happen rather than it being close cropped that would project the idea of cramped space with nowhere to move. Lastly the zoom or closer crop not only would show us the action of this horse but it would increase the visual interest because the viewer would then be able to make out more details in the face and the body.
while it show good thinking to leave the space in front of the horse to 'run into', the background could have been better controlled. The building in the background could have been cropped out. The tail seems more in focus than the head. well exposed.