IMO, #5 is the strongest of the lot, but would have been even better if you'd raised your shooting position slightly. Pets, like people, are usually best when captured with the camera at their eye-level. #1 is significantly under-exposed in the face, the camera's meter being "fooled" by the strong back-lighting. In #2 you have distracting elements on the RH side of the image, and the eyes are rather dark, other than that, it's not too bad. #3 is the same as #1, but even more extreme, and #4 is good, but there's too little dog, and too much empty space as well as a very distracting background. A tight crop on the dog would yield a fairly nice image I think, but it's a shame about the cropped forepaw.
Just my $00.02 worth - your mileage may vary.
~John