This question First story to feature the trope "the nice self-sufficient society that welcomed us are actually cannibals"? jogged my memory about a sci-fi short story that I read maybe fifteen years ago.
Two diplomats visit a planet to meet the high officials, a long lost earth colony; they are served a big steak dinner and all is 'laughy clappy' and good fun.
They are strolling back to their ship through fields, etc., and the junior remarks on the large number of farm labourers toiling in the distance. Are they the underclass mentioned at the meeting?
The older one comments on the planet's lack of any animals to function as horsepower, etc. He casually urges his co-worker to hasten until they're in the ship and blasted off.
The junior asks the problem, and the senior reminds him of the thick tender steak they'd eaten on a world with zero livestock