My granddad used a feeder like that at one of his pastures. His wasn't as modern, but the shape was the same. It was built on an old wagon chassis with steel-spoked wheels.

The understatement of the year is that cows are messy eaters. I'd bet they waste 50% of what they eat. Having the feeder moveable is a real plus, because of the hay+feces+dirt+urine cake that will build up around the feeder. When it gets too bad, just drag the feeder out of the way and scatter the nature-made compost out around the area.

The good thing about the feeders is that you can lay out a fair amount of hay, and it stays up off the ground so it won't rot. The cows can eat their fill and return later, even after a rain to eat some more.

Granddad had 2 leases around the small town (Bellville) where he lived. One had the rollaround feeder - he kept it backed up to the hay loft and would just pitch the hay out of the upper door. This was back in the days of wire-bound bails.

The second lease had the feeder attached to the hay barn under a shed roof. The detrius would build up under the cover to the point where the cows would start to rub on the top of the doorway to enter, and then we'd have to muck it out. We'd use a small lawn tractor with a blade and a makeshift ditching plow to rip & push the stuff out - took hours and hours over days and days to get that work done.

One other thing about square-bale feeding - on the whole I think it's a lot less wasteful than the big round bales. The waste with the feeder is limited to what the cows drop while they're eating. The waste on the round bales, especially as they're worked down, can be substantial.

I would expect the cost per volume is far higher for the square bales - lots more handling by humans for the pound. With only 6 head, I'd bet the round bale would rot before the cows ever eat all of it.

Of course, with square bales, you've got to feed practically every day - especially during the winter. I remember my granddad making the trip to each of the leases on alternating days throughout the winter - rain or shine.

Storing the round bales out in the open is very common - the outer layer of hay acts like a thatch roof - the inner grass stays dry.