I just saw your reply, now! Thanks for your input. He is currently getting 6 lbs a day split into 2 feedings. I am making the switch over to Progressive this week. I like the ingredients in the feed more than those in Purina, and logistically Progressive is easier for me to acquire. On top of the 6 lbs of grain he gets a pound of Manna Pro Max-E-Glo and Devils Claw supplement. I will also be adding Tri Amino in hopes of building his top line. He also gets free choice grass hay - I will be looking at some alfalfa this week in hopes to add that, especially with winter fast approaching. He also tends to waste a lot of hay - I do feed out of a net. I talked with the Progressive nutritionist as well about my feed plan.
His teeth were floated in the spring, although I have noticed some quidding here and there, so I'll have the vet out again here soon. He does not have any problems with grain at this time.
I will continue to weight tape him and take pictures. Unfortunately he is starting to get his winter coat in and it's going to be hard to tell soon if it's winter woolies or weight gain. It's not a great time to try and get weight on an old guy, but I'm going to give it my best effort.