I am changing from feeding a mineral block to loose minerals. I can't leave it out free choice because we have a horse and pony out in the field with the goats and I don't want them to eat it. Can I feed the minerals on their grain? Right now they get grain once a day. How much would I need to put on their grain so they get the right amount? They are Boer goats. I would be getting the loose goat minerals from TSC. Thank you for your help!