I felt less pressure to perform, or at least less angst and worry. It was overall just pleasurable; I felt it was as if someone removed all of the subconscious layers of expectations and judgments that are always present in human/human sexual contacts disappeared, allowing me to just be in the moment and for my sex companions to be there with me.
I think, or hope, a lot of men with understand what I'm saying. Sex with a human partner, which I certainly enjoy and keep enjoying, has many layers of emotions and feelings, intellectual thoughts, verbal and non-verbal actions which is what defines and separates our species. But other layers kick in such as touch, smell, taste, temperature, weight and pressure. And if that's not enough each person's body is being flooding with hormones like testosterone, and estrogen and at the same time there dopamine and a deluge of other brain and body chemicals. And there's the respiratory system, the circulation system, the other system, etc., all pump'n with the bump'n. All of these feeling are being experienced simultaneously.
Canine sex removes much of the higher level functions. The experience becomes more base, or if I can say this, bestial. There's an overall feeling of correctness, as though this is how sex should be experienced. I'm sure this feeling is because my ego was muffled letting my "Id" finally free from the life long struggle of repressing it.