The conversion ratio would hold if they ate the same things. Cows can survive on grass, which is often plentiful. Chickens more so on grains, which are harder to come by.
Chickens usually get fed grain because grain is cheap and plentiful and easy to dispense, but if you give them enough room to roam and vegetation to eat, they will eat it.
We used to throw all our food scraps (bit of bread, fruit, vegetable peelings) in a container and throw it to the chickens at the end of the day. They loved it, and would eat it all. We'd also collect rotting fruit from under the fruit trees and throw it to them. It would all get eaten. I found that pretty much the only thing chickens wouldn't eat were peach pits. Peach pits are way too hard, I guess.
In winter when we didn't have as much of a garden, we'd also let the chickens out of their pen. They'd happily roam around the yard, eating grass and whatever tasty bugs they can find. In the evening, they'd return to their chicken house in their pen and go to sleep. Very convenient.
I've come to the conclusion that chickens would happily eat us if they were large enough.
I believe that chickens are very efficient to raise. If you have enough vegetation around, you don't need to feed them at all.
In many parts of the world, certain insect protein is already palatable. To mention a few palatable insects I know of: the caterpillar stage of a specific moth species (Gonimbrasia belina)[1], locusts, termites[2] and - believe it or not - stinkbugs![3]
1. Also known as mopane worms https://en.wikipedia.org/wiki/Gonimbrasia_belina
2. capturing soldier termites is a fun, albeit occasionally painful experience for kids. Those giant mandibles can cut skin, and once closed, they never open
3. http://www.thestandard.co.zw/2013/09/08/bikita-villagers-sel...
Peach seeds (also apricot, cherry, apple seeds) contain cyanide and are poisonous. Maybe chicken are clever enough not to try and eat them.
This cannot be overemphasized. You can very efficiently dispose of all of your kitchen waste (minus banana peels) by throwing them at the chickens who will turn them into eggs.
In fact, years ago when we first started keeping chickens, there was a period where I would see food waste at cafes and restaurants and be seriously tempted to pack it up and take it home because, after all, I could turn this into eggs.
>If you have enough vegetation around, you don't need to feed them at all.
These two things are why you frequently see free roaming chickens in villages in poor parts of the world. They don't need feeding and minimal care or supervision is required.
In a rural setting whether there is plenty of vegetation available and few predators chickens are very close to being free egg and meat producing machines as there is virtually zero time or money required from their owners.
> Many breeds can eat whatever they find on the ground (although it’s better if you can feed them, because they’ll grow faster).
> ...for cows, you need to do all the hay thing, which is very time consuming and demands a lot of extra work just for feeding said cows