Many years ago we took in a Walker stallion for training. His owner was a Mark I Mod 0 Penny Pincher and wanted to use his own feed. When he delivered the horse he left a couple bags of his "high quality feed" (to use his words). The stuff was from some jackleg mill in KY. It was mostly twigs and leaves (literally). I didn't know they sold "crap in a bag" (except maybe as fertilizer). This stuff was more like mulch.
He was due to come back the next day to talk about a plan. So I got two empty, plastic peanut butter jars and filled one with his feed and the other with what we were using at time (a Purena product; I'm not sure which one it was but it wasn't the cheap stuff). I then put them on the back of my desk.
The next day he came in and we finalized the training for the horse. I then showed him the two jars and said we were thinking about changing feed and which did he like the looks of? He picked the Purena product and commented on how bad the other stuff looked. We then weighed it on a small scale I kept in the feed room and the Purena product was almost twice the density of the junk food. He noted that, too. I then informed him that the "junk food" was the stuff he brought. He started to object, but then asked to see the bag. I showed it to him. Without another word he picked up the "junk food", put it in his truck, and told us to use the Purena.
I can be a sneaky feller if I need to be.
The Moral of the Story is that horses eat by weight, not by volume nor by cost. The "junk food" we got was about 2/3s the price of the Purena, but was barely half its weight (and I shudder to think of the nutrition numbers). So it was actually cheaper to feed the better quality product.
A little molassas won't hurt an otherwise healthy adult horse. Good quality feeds use just a little. So the Object of the Exercise for a responsible horse owner is to know what they are feeding and evaluate that what they are feeding is proper for their horse and its activities.