Yes, Laying eggs can be painful for a chicken.

Based on my hens behaviors, I am guessing this.

My evidence:

When my hens laid eggs for the first times they squawked up a storm just as they would if upset by something. The first eggs laid are small.

After laying more eggs, a hen seems to become accustomed to laying and rarely squawk, but sometimes will. Eggs sizes do vary widely and sometimes double yolked eggs are huge! Brian Fey's answer to Can double yolked eggs be incubated as successfully as single yolked eggs?
I interpret this to mean that the first time there is some discomfort beyond "Whoa! An egg came out of me!" I suspect physical pain. It makes sense since other animals also experience pain when giving birth. Holes have nerves generally.

Is that proof that a chicken feels pain when laying an egg? Nah, but it seems likely given the circumstances.

A better test:
I guess there could be a way to measure brain activity when a chicken is in pain and then compare that with when they are laying an egg.

Source: https://www.quora.com/Is-it-painful-...ns-to-lay-eggs

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