This makes me wonder - would chickens grow more efficiently if you cook their food for them?

When we invented cooking it gave us a massive advantage because of the nutritional efficiency, yet we feed animals just random raw stuff. Would feeding them porridge instead of grain lead to higher output?

> When we invented cooking it gave us a massive advantage because of the nutritional efficiency,

I was reasonably confident cooking reduced nutrition but reduced food-based disease way more.

Your proposal may give interesting results in a couple hundred generations of chickens, when evolution has had some time to take profit of the cooked food. But, concerning the hens that lay the eggs I'm supposed to eat, please refrain from experimenting with them, thanks!

My chickens feed is a grain mix that can be boiled or even fermented, often called silage with the larger livestock.

The chickens love some warm mash on a cold day like today, they'll get some yogurt too.