It's less a biological question, and more a question of the laws regarding meat production where you live. IIRC, in the US (just some states I believe), chicken

It's less a biological question, and more a question of the laws regarding meat production where you live. IIRC, in the US (just some states I believe), chickens for example don't need to have space to move at all, except maybe a few inches. We quite literally turn them into machines for producing meat, at scale. Further, the breeds of chickens used for meat are usually for meat, eggs for eggs, etc - at least at the industrial scale.