Looking for 2D or 3D?
For 3D:
Leaf on Fire basically a scene grinder. Sadly abandoned cause copyright but still lots of good content. One of my favorites
King's Tale a bunch of short stories. Basically all the same formula of story but different models. Also abandoned but might be getting picked up by someone else in the future
The Pilgrimage more monsters than straight up animals but tons of content, regularly updated, good models.
Tentacular great game, voiced girls too. More focused on tentacles (you're the tentacle monster) but still some animals and weird stuff
Project Myriam while not focused on bestiality, lots of good beast content. Wish there was more
Miri's Corruption sadly on hold for now, but there's lots of good horse stuff
For 2D:
Claire's Quest lots of beast content, not a singular focus though. But a big path of it is animal focused
Beast vs Bitch 2 and
its prequel. short but sweet
Slice of Venture Origins LOTS of beast content. follow the walkthrough to get all the side stuff
Cocoa and Taro The Game it's on my to-play list, but it's decently rated
Miscellanious:
Jacki's World HTML game, good amount of beast content. didn't explore the rest
Hope this is (kinda) what you asked for - I know the pain of trying to find beast-focused games on this site. Sadly, they're few and far between