How can I buy quality Oats?

I am an old timer that believes oats are the best feed for horses. No founder, no colic. I buy whole oats at a feed stores in 50 pound bags. The quality varies a LOT. The tag says 100% oats or oat products. No mention or claim of FGIS Grade or weight per bushel or cleaned or dust free or anything. I opened a bag Sunday that was so dusty that I opened another bag and stuck my hand down in it to get a handfull and found golf ball size chunks of moldy grain. I took those two sacks back and they replaced them. I got home and opened one and the oats are very, very light with lots of straw. Years ago I farmed and when I sold grain, they took a valid sample, tested and graded it to establish the quality of the grain.  

 

Is there any way to buy what I can expect to be good oats? by the bag or the truck, I don't care, just so I get good oats.

How can I buy quality Oats?