I love this photo—it brings me a lot of happiness. I love the dynamic between the two main subjects, a horse and a dog. They seem to be at odds, almost ready for conflict, with the dog poised to spring forward and the horse tilting its snout away as if in anticipation. But the idyllic backdrop, soothing colors, soft light, and calmness of the horses in the background make you feel as if nothing is wrong here and that everything will be okay.
The fence between the two subjects bisects the image both visually and for the subjects. The horse's (top, far) half is full of light and ethereal color, and the dog's (bottom, near) half is shadowed and full of dark earth tones.
The horses in the background imply a power dynamic. Here is a lone dog amongst a herd of horses—boldly confronting one of the herd members. The other horses don't seem too worried though.
The portrait orientation of a picture that could have been captured in landscape reminds the viewer that this scene is taking place in a much greater setting, which you can appreciate all the way from the dirt to the sky.
This was taken on a Leica Q3, which I have found to be the best lens for capturing dynamic moments while still maintaining a lot of beautiful character. It also allows you to remain unobtrusive in the scene, blending in and allowing those around you to behave as they would.