edit: Or chicken for that matter, google what happens to the male chicks.
Depends on what country you're in. For the curious, they're destroyed, as they grow too slowly for meat and don't lay eggs. In the US, destruction involves them being chucked, peeping, into a large grinder. In other places they may face CO2 asphyxiation. The maceration method I think is more humane and instantaneous, though it is certainly violent looking.
Some living beings do not experience air hunger when Oxygen is substituted by CO2. Not sure if that is the case for poultry. I wouldn't be surprised that's the reason CO2 asphyxiations is even a thing.
Suckling pig, also Cornish game hen, which is not a game bird and is equally likely to be a cockerel as a pullet. Technically, a female chicken is not known as a hen until it begins laying eggs. https://en.wikipedia.org/wiki/Cornish_game_hen
Not sure how we got here, GP was talking about human children.