I've never even heard of that, and I know a few farmers.
Yeah, chickens can be hypnotized. Takes about 5 minutes to learn how.
Very few farmers spend time hypnotizing chickens, because after they're in a trance, they still no speaka da English.
Therefore, regressing them back to an egg isn't too feasible, and post-hypnotic suggestions to lay a whole bunch of eggs a day are lost on them.