"...Yep, it was a far better environmental solution back in the 70s, when cattlemen built huge feed lots with 10,000 or more head and kept them all cooped up together..."

The '70's??? Drive by the Harris Feed Lot, second largest in the county last I heard, on I-5 in central CA today and you will see between 80k and 125k head of cattle in a pretty small area. Side note, many are fed a special high fat diet and flown to Japan on 747 bull haulers. John Harris, son of the founder Jack Harris, is a rich man...

Oh yeah, they're still around, just not nearly as abundant as they were when I was a kid. I saw an awful lot of them empty out in about a decade. You can still find em, remnants of an era.