WASHINGTON (AP) — The freedom of a hen to flap its wings and move around became an issue of congressional concern Thursday as a Senate committee discussed legislation to set national standards for the treatment of egg-laying hens.

The debate over how much space hens should have in their coops has drawn the attention of other livestock producers who fear that they’ll be the next target of animal welfare advocates, and has become a states’ rights issue as some states try to impose their tougher standards on eggs coming from other states.