They produce meat more efficiently than any artifical process, especially any process line using nuclear medicine.
And for what it’s worth, there is no other mechanism that converts indigestible starches into highly digestible proteins.
It’s not like everything put into an animal is converted into edible flesh, not even a tenth of it is.
The typical chicken caloric conversion rate is 2-5x. That means 10000 calories of feed produces 5000 total calories that are higher quality than the feed was, about 2000 of those calories is meat, where the remaining 3000 is used for other purposes, like creating broths. This is incredibly, miraculously efficient.
Real-world numbers seem a bit better. 100-320kcal/day (more in winter and as they grow) per day in feed, and produce 2500 of straight meat after 40 days. That looks like more like 4x conversion than 5x.
Egg-laying chickens have a ramp up (where you feed them but they don’t produce eggs), but then produce an egg almost daily. That’s 80 calories in eggs for 260-340 calories in feed. (so almost 100% return on the extra cals). And yes, you can still eat the chicken when she’s too old to lay eggs. She’ll just be a bit more tough.
So if you’re comparing the production of meat to burning gasoline, then no chicken is not as efficient. If you’re comparing it to any food-related process (or hell, many mechanical processes), it’s downright jawdroppingly good.
Compare to corn. Only 10% of the calories in a typical grain crop are edible by humans. You’ll never guess what we use most of the other 90% for.