“While free-range egg farmers would prefer their birds to be outside, they also wouldn’t want to risk the health of their birds. Their sheds have plenty of room for the birds to move around freely and include scratching areas so birds can still display their natural instinctive behaviour.
Farmers have also put in additional stimulants like footballs, cabbages and even Christmas trees to keep the birds happy.” https://www.theguardian.com/world/2017/feb/28/eggs-temporarily-lose-free-range-status-due-to-bird-flu-restrictions
In ancient times, jungle fowl were originally domesticated for their invaluable natural instinct to peck up fallen pine needles.
After perfunctory testing on chickens, cabbage is set to be marketed as a natural alternative to recreational stimulants.