Yeah, my family has a farm and we hired a farm manager who had owned his own conventional farm before he worked for us, so he wasn't really up to speed with grass-fed. He insisted that the cows needed grains in the winter and I was like "nope" and I hired a grass-fed consultant to tell him that there is something called hay which is dried grass. D'oh. He never would have listened to me though since I'm not a farmer. In the winter you feed animals you want to keep grass-fed dried forage like hay with some supplements like alfalfa.

However, PUFA content is so low in ruminant meat that I personally don't worry about eating animals that had a little grain. I think it's suboptimal for them and us though.

I'm in northern Virginia, too, and I'm pretty sure there are farms in Loudoun county other than the one I go to (which doesn't sell at the farmers markets) that are pastured. I can think of a few off the top of my head. In the winter I believe they rely more heavily on hay, but I still see some green grass out in Purcellville so I know there is plenty of stuff to eat.

I live in Ohio and raise 100% grass-fed lamb. There is no reason that lamb can't be 100% grass-fed. Most farms that raise grass-fed lamb coordinate the breeding of the animals so that the lambs are born in the spring out in the pasture. This gives the lambs a good six months to grow to butchering size, without having to feed grain. The lambs are taken to the butcher when the grass growth slows down in late fall. If, for some reason, the lambs are held over through the winter, they will continue to grow or, at minimum, maintain their weight on high quality hay.