When I was in college in Kingsville, I worked in the oil field on the King Ranch for 3 years. On any given day, we would be all over that thing. We even got lost on a few occasions.
As far as your question, I do remember that John Deere would bring in prototype tractors (under covers for security) on the ranch to put through there paces. I guess they didn't want the competition to see what they were working on. They would work large pastures in desolated areas, but I think it was more shredding, root plowing and discing. I don't remember ever seeing "hay pastures". The only place I saw cattle feeding on hay was at the pens that are located on the tourist drive near the main house. They always had a few steers and cows for the "snow birds" to look at.
Secondly, I remember the ranch had there own feed mill in Kingsville.