why do you think that the first thing we are told about Mr Jones is that he locked the henhouses?

Yes, the first thing we read about farmer Jones is,

“Mr. Jones, of the Manor Farm, had locked the hen-houses for the night, but was too drunk to remember to shut the popholes.”

This is the image we get of Jones and really humanity as a whole. He is a drunk and he is mean. He controls and he punishes. It is as if being human, like Jones, is an inherent disease which we think the animals are immune to.