A few additional thoughts on the image.
The main issue I have with this image is the harsh lighting. The camera left side of the dog is bright and the camera right side is in deep shadow. I can't see the EXIF data on the image, so am not sure about the time of day this shot was taken. A bit of fill light would help here, but I can't imagine you had a speedlight along on the walk with you...
Probably the first thing I do when I am out with my camera is to look at the light and if the light is not working, I won't (generally) take a picture. I find that animal images seem to work out a lot better in overcast conditions, when the light is nice and diffuse. The fur really shows up nicely. Alternatively, even in sunny weather, the shot often works better if they are completely in shade.
Sometimes centring the subject works quite nicely, but I still tend to look at composing to the "rule of thirds", and will try to place the subjects eyes on one of the horizontal third "lines" or will try to place the subject a bit more assymetrically.
What does work here, is that the background is soft and out of focus, so you DoF choice works well for you and the background does not overpower the shot. However, I do find that there is too much background for my taste. I feel that the subject of the image is the dog, and you don't want the background to compete with your subject. so finding the right balance is the real trick here. After all, you are trying to show that you are out for a walk in a really nice setting.