Horses with fly masks on always make me laugh, they remind me of the Lone Ranger or some other masked character. These two remind me of Batman and Robin, the image just makes me smile.
Technically I love the composition with the horses in the bottom right portion of the image, allowing a framing in the image by the trees and also the fence posts and rails creates a line that leads the eye to the horses. The colours look like they have been adjusted ie toned down? it makes the image look black and white from afar, but with a closer look you can see the clever use of the colour.
Overall an image that is technically spot on, an image that holds the eye and lastly a happy image. It makes the viewer smile.