It does of course depend on just where you are and your local climate, soil type, elevation etc as well as your stocking rate, as you say Steve. Where we are the grass is dead for most of the winter (Nov to March/April), hence adlib hay, so if they need it they take it. Sometimes it grows for a week or so in Feb to give them a welcome bite, but we have to plan for 5 or 6 months of feeding.