At two pounds a day and you can split that if you have a concern, the Purina is not high sugar or starch from what I ve read.
The middle used to be Pro Add Ultimate. I have a hard time getting it around here but there was a time I used it for my several of mine. I really like it. It did enough better than the Nutrena Topline that it was worth the added cost.
Some horse people change their horse, they change their tack and discipline, they change their instructor; they never change themselves.