Can the DSMR Protocol be used, as is, on companion animals, including dogs, cats, and horses, and will it be effective in helping them with needed healing?

It can be used exactly as you do with human clients. If you are channeling, it will go quite nicely and will be an interesting and instructive exercise. The key is that you are using Creator's translator, so any true channeler using that approach will have no trouble getting interesting and useful information, but that is not necessary. As with human clients, the key is to get the healing launched. So with the aid of Creator's translator, conveying the steps of the Protocol you would use for human beings, will be translated for an animal in a way appropriate for them to do useful work, to bring about a positive benefit, and it will work just fine because adjustments will be made for each subject to take maximum advantage of the intention of the Protocol, for any stated goals of the session to be done with the aid of the divine realm, and this we will carry out following your lead.