None. But in the wild, almost all eggs are fertilized in birds... Chickens are jungle birds originally. Man domesticated them. Now they are warehoused in huge buildings, their reproductive system hijacked for your morning breakfast.

Many live their whole lives in cages, never touching the ground.

Human equivalent, yes probably menstruation. During most of human history, the average woman had 13 pregnancies, and 9 live births in her life time. She was lucky to raise two to teenagers. This is still the case in areas of no "imported" medicine, such as the bush of Africa, or the rain forests of the world.

Modern medicine in First world countries now saves most babies, and most mothers.

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