These strike me as a strange couple of lines to trot out...
"DH was cuddling her and rubbing her tummy (does the same with the dog)"
"There was no sexual element to the tummy rubbing, DH was brought up with a lot of dogs..."
Is he Mowgli? 
I was brought up with a lot of dogs. I was also brought up with other humans and fully understand the varying boundaries and the implications of crossing those boundaries with regard to sharing affection with these very different species!
Your daughter isn't a dog, your husband needs to be aware of appropriate touch between adult male and minor female regardless of relationship (or his upbringing!).
Your daughter needs to be aware that particularly as she matures, there are areas of her body which no-one has a right to touch, mindlessly or otherwise, without her consent. Even if, in fact, particularly if their understanding of appropriate touch is skewed, for some outlandish reason.
If she rubbed his tummy in a similar way, would she/he/you feel entirely comfortable?
I doubt there is an issue of sexual abuse but I do think young women should be encouraged to gain an understanding of what is comfortable and appropriate to them, to wider society and the whys of such and further encouraged to voice their expectations and rights wrt other people's touch of their own bodies.