Let's see...roughly ZERO. Nobody can change their sexual orientation. It is an inborn trait built into the wiring of their brain.
I don't know where you're reading those profiles and you're just pulling that "50 or 60%" out of your äss, but clearly you really don't know anything about furries and have spent no time getting to know the fandom. If someone who formerly seemed straight reveals him/herself to be gay sometime later, it has nothing to do with being a furry or anything else. It has to do with realizing one's true feelings and attraction, accepting and coming to terms with it, and feeling comfortable and confident to open up and tell others. Formerly the person claimed or believed oneself to be straight because of the social pressures and fears that they grew up with telling them they must be nothing but straight, resulting in that person denying their true orientation to oneself.
The furry fandom is incredibly diverse, open, and accepting to all people of all demographics including all sexual orientations. People who are GLBT can very freely be out and open about themselves with no need to hide it. When someone who is closeted GLBT joins the fandom, that person sees everyone else of whatever orientation or gender identity very freely and comfortably being open about oneself. A gay person doesn't have to hide being gay and same-sex couples don't have to hide the fact they are a couple in love. They show very clearly that gay individuals and couples are friendly, fun, loving, and accepted, and all that can inspire even the most closeted non-heterosexual person to accept his/her orientation, be proud of it, and come out to the world without fear. While the furry fandom has nothing to do with sexual orientation or GLBT pride, it has everything to do with freedom, free expression, personal liberty, pride to be just who you are, and acceptance of one another as equals.
That's probably why you see some individuals join the furry fandom and then come out as gay later. That person was always gay; he/she just learned to love and be proud of his/her true self and stop fearing it by being inspired by this really awesome furry fandom.