Understanding what set recipe & least cost mixing is when deciding what horse feed to buy is VERY important. Here is a video to show HOW you can determine if this is the case.
 

Equine dedicated mill is the first thing you should look for to determine how safe a horse feed really is. This should be the first thing you consider before deciding what brand of horse feed you should be buying.

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?