How to determine what makes a quality horse feed?

Here is a checklist with what to look for when determining what makes a quality premix horse feed:
1. Safety - is it made in an equine dedicated mill?
2. 'Set recipe' V's 'least cost' mixing
3. Does it contain high quality protein? 
4. Is the feed digestible?
5. Does it contain what the horse needs?
6. Does the feed manufacturer have good raw material quality control?
7. Do you get what you should be getting?