In
Ronald-1 (changed from
Ameglia when no one would get the Hitchhiker's Guide reference), domestic cattle are genetically identical to Baseline cattle but sentient and capable of speech, and highly insistent that they should be raised as farm animals, killed, and fed to humans. The belief might be religious, but even "atheist" cattle will be adamant about this.
This has caused a whole lot of philosophical debate, which started getting political when major Baseline food companies got word of it.
It only got worse when
Ronald-2 was discovered, where cattle is also sentient, but militantly
opposed to being eaten and extremely paranoid about the prospect. (Consider dusting off your old Traveller books here.)
Trying to think up one based on the phantom time hypothesis (
https://en.wikipedia.org/wiki/Phantom_time_hypothesis). maybe a 297-year time loop?