All depends on the oats who is putting them in the bags. Most feed grade are terrible and I wouldn't feed them to the rats. But, we have bought feed grade from Wiloc Farm store for years and they are better then the cleaned horse oats..
They did start using a different supplier and they are not as good. But, still nice oats.. I have been feeding them for YEARS.. My horses love them and they are all in good health and not one of them look like they need to eat..
Yes JJJ, oats and any other feed can sour. So can beat pulp. You have to only soak what you are going to use that day just like beat pulp. My friend who soaks them feeds them that day.. She has never had them sour and certainly wouldn't feed them if she did.. She is one of those fancy pants Arab breeders..
None of mine have ever had trouble chewing them. My older horses and the foals all love them. Horses that have chewing problems will with any feed that is not a soft pelleted feed. Grain mixes often have barley, corn and other stuff in it that would be hard for a horse to chew that has this problem..
There are a million good feeds out there. I use what my horses like and it does not cost me an arm and a leg. Likely JJJ, the reason the oats are so spendy in your area are all the halter fitters trying to get all that incentive fund money running the supply short..