4 month old, how much to feed?

My filly is being weaned (no longer nursing in the field, but still in the same pasture as her dam) and has demanded she eat in another bucket than her dam. How much should I feed the little one? In whatever unit of measure makes you happy! She's about 4 or 4 1/2 months old, 12.2hh, and has been on a high end mare and foal feed so far. Also, is there a feed you would recommend for her?

Thanks!

Look for a good quality fixed formula low grain no grain feed that is high in nutrition .. watch your Ca/P ratio to insure that it is as close to 2;1 as you can get to avoid DOD"s ... and fo course good quality hay offered free choice is a must

I have a six month old filly and I like to keep food in her almost all the time so I generally give her two flakes in the morning and two at night