Yes, what you think is happening in that image above is exactly what is happening in that image above. Ubisoft actually created an animation for a bull to mount and ride a cow.
This particularly disturbing image is from the Testy Festy side quest, where you are tasked with acquiring three different types of bull testicles to be cooked and eaten -- flambé style (kill 'em with fire!), shredded (mulch 'em with the death tractor), and "blue" (take 'em out while they are doing it!).
For those wondering, yes, the Testicle Festival is a real thing in Montana, and they really do serve bull testicles cooked in a variety of ways. If the apocalyptic Seed cult didn't convince you to stay out of our state, maybe that little factoid will do the trick?
Image courtesy of GameSpot