For this problem I have made a machine which smashes the GRAIN in a way that one seed wont fall apart it is as one but smashed, In this way you will not see one piece grain in the horse droppings.
I always have mixed GRAIN with the ALFALFA and HAY in their feed pan this has slowed them down from taking excessive amount at once in mouth full. It also increases their fiber intake. I have also noticed weight gain in a months time and my horses seem to be more relaxed and less excitability at their feed time .
Mix one scoop of Grain and some amount of Alfalfa. You can also put some feed on top of Hay in their feeder. Adding water will also slow their eating and will benefit their SWALLOWING by older horses.
I think in general many of the Horses Lameness are coming from Diet and Weight of the Horse.
The most pressured part of the Horses body is the Hoof and in the Hoof the most pressure is on the HEALS therefore we have to watch the Horse weight and diet.
Keeping the Horse weight in normal depends on the amount of Forage , the Diet , little amount in 4 to 5 times a day , Do not allow the Horse to have Food at all time.
If we compare the Natural Horse Diet we will see Horses because of running from one place to another from the predator they don't have the food and water at all time they eat and drink little amount in different times during one day , don't worry about the Horse not having too much food at once , We are not doing good by giving them too much food at once and all day long present for them.