People love their Pets more than their fellow humans. The Pet Food and Accessories Industry is huge and has been for decades. The fact that you purchased both singular and plural tells me you want to, at least subconsciously, pursue this concept and peoples love of their canines makes this idea totally feasible.
Development wise, it would require paying postage for dog food to any Joe Blow that request one. So in it's "free' sample use, would need a big, very committed buyer/developer
Find this buyer/partner, this is the primary logistical hurdle.
Why do you think you could 'flip' these names? If they were flipable it would have happened by now. These names are for development. Either develop or break even with maybe $250 profit from another end user sale, whom I'm sure will fantasize about flipping them after realizing Johname's key point.
Regards.matt