Kind of off topic but relevant, it is probably once again the processed grains/foods/breads, etc - if we shouldn't be eating it, we shouldn't expect our horses to be able to. Remember how skinny everyone was in the 70's? We didn't start getting fat until about 20 years later when it became easier to buy food in a box rather than out of the garden. So, that's probably why horses get sick now but didn't then, same with house pets and tablescraps. It's what is in the food now that wasn't there back in the day.
I would have thought it was a pretty expensive way to feed horses - a lot of bulk for not a lot of 'goodness' - unless you got stale throw out stuff from a bakery I suppose
I don't see it as a great idea
My Grandparents told me that they fed the work horses on cooked potatoes in the war and they were good for weight gain
Boiled oats/barley put weight on horses better than feeding them plain or crushed/crimped
I have no problem feeding stale bread as a treat every so often, but it's sadly lacking in the proper nutrients to use as a regular foodstuff.
The majority of a horse's food should be in grass or hay, with feed added just to round out what vitamins and minerals they may not be getting in their forage. I've followed this plan for many years, and my horses are sleek, shiny and healthy.
In Germany lots of people give the "old" bread to horses! In fact everybody I know does it over there.... I do not anymore as I am in Canada now and I hate the bread here so there is no bread in the house :0)