Vote up any answer that you think is good. There's absolutely nothing wrong with voting up all of them, if you think they all offer good advice.
However, I strongly disagree with the idea of splitting them up into separate answers, one suggestion per answer. That is exactly what we want to avoid (they're colloquially referred to as "me too" answers).
Each answer should be as complete as possible.
If you think 2 of the suggestions are good, but have an issue with the third, its up to you if you think the overall answer(s) is helpful enough to upvote, or bad enough to not merit a vote (or even a downvote). You may also want to add a comment to one of the answers indicating your concern, if you think it will help the quality of the information.
If your objection to that one suggestion is that you don't consider it particularly effective, I'd personally just ignore it. However, if your concern is that it is potentially dangerous, or otherwise detrimental to the health of the dog, I'd consider posting at least a comment explaining your concerns, and possibly a downvote.
I consider this more of a "shopping/recommendation" question than a list question. The discussion on shopping/recommendations shows this particular question as probably within the bounds of what we'd consider acceptable.