Luna From the Manage Hay Page: - Grain Supplementation - You may feed Health Blend grain in place of hay. 1 Pound of Grain will cover one feeding.
And since if they don't have a rider they won't be trained and it doesn't stop you from training, you should be able to not feed certain horses so long as they don't have a rider.
Good god. I wish we had the option to only feed show horses.
As a colour breeder who I dont show colour horses just show my gelding army I'm building. The cost of food for all of my horses is outrageous compared to the cost if it was just my geldings...