I've gotten moldy or bad feeds before from every feed store and mill in my area. We have about 4 different stores, plus two different mills.
All have taken them back and opened new bags for me to inspect before replacing the bad bag, so in my area that's not anything connected to just TSC.
I personally do not like the Dumore feeds for any of my farm animals because whenever I have been forced to use them (mostly for poultry) there has been a decline. I have had good luck and great results using the Nutrena line of feeds for my horse, but have also tried Triple Crown, Buckeye, Purina (other feeds, not the horse feeds) and a few of the store brands.
Again though, I base my opinions of the fact that I'm feeding 5 different kinds of animals and the results I see across the board, in addition to the fact that Nutrena has proven the best for my horse.
Also like the Standlee products. Sometimes I need to add hay stretchers for my other animals in the winter (my horse doesn't need it) and their hay based or alfalfa pellets have worked best on my farm.