My ex and I discussed it and the thought turned her on. I don't think we ever acted on it. That was 35 years ago. I kinda recall, maybe our female mutt did lick her once, with a little peanut butter enticement.
After the divorce, I was single for 18 years. Did some swinging and introduced a few gfs to swinging, too. During those years, I had two big labs. First, a chocolate and after he passed, a yellow. Both licked several pussies over the years. Only had one slightly negative experience...semi-long term gf/fuck buddy who I'd got into swinging, etc. One night had her blindfolded and bound, lightly and told her she was getting a new experience. Put some PB on her cunt and let the chocolate start. As soon as she realized it was the dog, freak out, screaming, etc. Stopped let her loose, finally calmed down. Didn't do that again with her. Though later she confessed she overreacted. But, our time was about at an end anyway.
Few years later, chocolate was gone, had the big yellow and I can think of 3 off the top of my head that's he licked, including wifey. None complained! He passed a year or so ago. Time to find an intact lab and continue the adventure. K.