The result of too little light and too high ISO
Lack of contrast and the increased ISO value made a lot of digital noise. The exposure meter can't deal with the white snow in the corner of te photos.
-and the right way to do it:
Beautyfull eveningsun and a dark background, all tree
photos are taken with the same camera
OR...
TAKE THE PHOTO ANOTHER DAY OR ANOTHER PLACE.
DON'T COMPROMISE ON THINGS THAT WILL MAKE YOUR DOG LOOK BAD!