I’ve had a similar experience, and in fact I went much further than the author of the initial letter. It involved the dog of a friend of mine, with whom I was staying for a few days.

My friend and her husband had gone out for the evening, leaving me alone in the house with her dog, a golden Labrador bitch, whom I knew quite well, and who seemed to like me; I had already fantasised about having sexual contact with her, and found the situation highly sexually arousing. I invited her to come along to the bathroom with me, where I proceeded to strip off. There was something I found exciting about having her watch me undress, especially when I pulled my underpants down in front of her, letting her see my erect penis. (It must be said, however, that although she kept her eyes on me all the time, she didn’t seem very impressed.)

I then proceeded to masturbate, stroking and fondling her at the same time. I touched her more intimately than usual, playing with her nipples and stroking her belly quite close to her genital area. She seemed to enjoy it, though not necessarily in a sexual way. I stroked her right down her belly, further than I usually go, but I didn't at any time touch her vulva. It was a nice feeling to have another living creature present when I was masturbating, even one of another species.

I didn’t tell my friend or her husband about what I’d done. They’re both pretty liberal, but a thing like that might have been a bit too much for them to go along with. I thought they might be appalled, and I simply didn’t want to risk that. I did feel slightly guilty about keeping it from them, but since I hadn’t been doing anything to hurt the dog or them (neither of which would I have contemplated), I reconciled it tacitly as being OK. (After all, I felt it was just sex.) I’ve done it on other occasions since, when I had the chance, and even began to look forward to staying with my friend so I could have the opportunity to do it again - though not, of course, purely for that reason, nor did I do it on every occasion.

I still sometimes feel guilty about having done it and not told my friend, whom I like sharing things with, but telling her anything so outrageous appeared to me to be out of the question. I sort of excused it on the grounds I was sparing putting her in an extremely awkward situation with regard to how she feels about me and the dog (though that may seem rather trite). And that may be the same with the author and her male friend.

As to the idea of getting a dog of your own if you have zoophilic tendencies: perhaps bizarrely, I wouldn’t be keen to get a dog because of any sexual feelings I might have towards her. The reason is that it would be too much like owning a sex slave. My friend’s dog was free to express any feelings towards me that she wanted, so the fact that she went along with what I was doing made it seem alright. A dog usually tries to please its owner, so may feel obliged to take part in sexual activity, even if not wholeheartedly in favour of it (though make no mistake, if a dog really objects to what you’re doing, it won’t go along with it - as I know well from observing my friend, along with her husband, trying to wipe her dog’s paws when she’s been out in the mud!).

Mind you, the mild sexual feelings that the author experienced while with her friend’s dog – which may not even strictly qualify as ‘zoophilic’ - would hardly come into any such category, so I feel her getting a dog would be a fair enough idea – though I’d agree with the previous writer and suggest she does it only for the right reason.