We can only hope that a loving relationship, and not a relationship based solely on a sexual one, is the reason he's searching for a mature female dog. Funny enough, when my zoo friend gave me my Newfoundland girl, he didn't even mention how hyper-sexual she was. Only that she was gentle, smart, and loves other people and dogs. Maybe he was just testing me? Who knows?
For those reasons, and the fact that when she initially met me and my mutt mix, we all got along. I decided to take her in, since she desperately needed a home. (I'm sadly her 5-6th home, the other people he rehomed her to ended up being shitty, and he kept having to bail her out.) Her being a nympho was more of a delightful surprise.
Yes. Like that. I think that for you, like us, respect for our animals and our obligation to *them* comes first and foremost. Sex -- if there *is* ever a sexual aspect to the relationship -- it's always just an option we leave open. Encourage it? Invite it? Sure. But it's definitely not the
reason we've adopted any of our dogs, and it's never required of them.
Consider that in adopting older dogs, you have no idea what their history has been. Was this dog or that one ever abused (physically, sexually, emotionally?). Was it ever neglected? Friendliest dogs in the world may have a trigger point you just wouldn't have guessed. Some little thing you do and *snap*! Surprise the hell out of you, no idea where that came from. Shelters, rescuers and private owners try very hard to let you know "all about" the dog before you commit to taking it home. How is it with other dogs? How is it with children? What age children? -- But they just can't tell you everything.
The very first thing the older dogs we've adopted needed to learn was that they were safe here, and to trust that this was permanent. They were "home." They were family now. It's not an instantaneous adjustment. Likewise, we had to come to know them, to trust them.
Recent example (deceased now three years, I guess): One old loving doofus we adopted at 6 years old (intact male with a huge package! ... couldn't help noticing that first thing) seemed like our dog the moment that we saw him. There was just this "connection." We got to walk him, learn about him, etc. Then we went home without him. A week went by and, yep, we were certain. That great big old dog needed to be in our home. He'd been in that old shelter too long.
He was just a big old gentle giant, timid, even -- until I went to put his new collar on a week or so after we'd settled him in our home. He whirled around and slashed at my hand and continued crouching and snarling at me, barking savagely (very loud voice, this dog). This was a total shock, a complete 180 in his temperament. I stood firm, maintained dominance (but out of reach, of course). I was able to talk him down but took some doing. But I gave up trying to do the collar just then. He was a huge dog capable of inflicting considerable damage. And yeah, my first thought was: "Oh hell no. No no no. He's going back. I can't have him doing that." That defensiveness, that hostility, it was something we always had to watch out for after that. Didn't really turn on people after that. But turned out he did *not* tolerate small dogs. He'd try to kill them. Oh, and deathly afraid of storms. Afraid of *rain*. Heck, I think he was afraid of gray cloudy days.
No one told us about this streak in him. I don't think they knew. We always wondered what his history must have been. How did he get like that? What had happened to him? But we managed. We loved him. And one of the kids, he just melted around her when she visited (she was in her 20s). And he became a beloved member of the family. His big old paw prints hang on our wall and two of the kids' walls at their homes. That favorite daughter has his ashes on her mantle.
Sexually? We had tried a couple times. He would let you jack him. You could suck him. Or try (enormous tool). It "worked," it got hard, big knot, lots of squirting cum -- but just really wasn't interested. Indifferent to it, might be the word. Tolerated it? Didn't seem to enjoy it, just "allowed" it. So, we scratched that off the list. Physically, responsive. Mentally, psychologically? Wasn't there. Just not fun sexually with him. We don't enjoy coercion, "concession." It's abuse.
But he did become playful with us, otherwise. And he was an absolute nut for snow. He thought nature did that just for him. He bounded around in it, tried to snap snowflakes out of the air, dove into it and rolled around, wriggling. There's just something about "your" dog, when your dog becomes "your" dog, and you become "his." It's just magical. You didn't know each other previously, but now you seem as though you've always been together. You are committed to each other. Period. Faults and weaknesses included. You belong to each other. Home.
Just saying all this as a word of warning to the OP -- Lots of things to consider beyond just, "Are her reproductive organs intact." Finding the dog is one thing. Committing to the dog is entirely another. Sex is a happy option sometimes. Sometimes it's not. You won't know right off. Takes time. Fingers crossed.
-- And of course, none of the OP's question concerned this. The question was just "Is it possible to find a mature, intact female." More wasn't mentioned so, just making sure this other stuff is also considered. If not for the OP, at least for anyone reading this thread with similar ideas.