If your ethical code is a variation of 'reducing pain and increasing pleasure for all sentient life' this would be orders of magnitude more good then the Peta option of turning them loose to die in the wild or never exist. It would be far more ethical than even artificial meat.
Heck from a strict cost/benefit analysis it may be one of the greatest moral triumphs mankind has ever given the universe.
Why would an industrial food processor care about how luxurious the sentient inventory finds the warehouse?
There is some chance that I will accept the deal, just to buy more time and find weaknesses in the aliens. Anyway, I would prefer to die free on my own, and I would prefer that my family gets to take my body and cremate it, or give it to earthly elements.
Lets say aliens came and offered you a deal. You can either not exist or live a life of luxury with all delicious food and mates you want, then after 1000 years or so you'd peacefully pass away just like a natural death and you are informed that they'd eat your body. I'm pretty sure quite a few people would be open to this.The choice is even simpler with animals since from all evidence they lack the capacity for existential dread.
Now tell, me what would be the most moral choice assuming chickens are sentient? To indulge them to a pampered existence several times their natural lifespan...and yes, at the end disposing of their bodies in the most practical and beneficial way, its not like a chicken cares what happens to its mortal shell in whatever poultry afterlife may exist. Or leave chicken minds to the terror of being torn up by a fox in the wilderness or to never know the joys of existence in the paradise future ethical meat farms may offer?