I think I get Martendale from my dealer, but probably wrong on that. I don't have a free choice feeder yet, but have used a trough and corn mix in another timed feeder for some time. I pay around $11-13 for 50# bag
I use 21% until Spring green up, then drop to 16% through june or so, when natural grub looks poor, I will bump it back up to 21% through end of Oct.
You would be smart to see what your local feed store carries, or one you pass on the way out, convenience can save allot in fuel.
Friends don't let Friends drink and post.......
The first 5 day's after the weekend, are the hardest....