I just resently purchased a 8 year old and a 20 year old minature donkey. My question is how much do I feed them. Does the 20 year require more grain. I'm presently feeding each about a 1/8 cup of Omolene 100, I top dress with their minerals. In the morning they're out on pasture for 3 hours, in the pm I give them a flake of bermuda hay. Thanks in advance for any advice.