I have a 41/2 month old foal that has been eating a mare and foal pellet since he was a week old.  He was eating four cups daily but he has recently stopped eating it.  It began last Wednesday morning. He turned his nose up to his am and pm feeding. I didn't think too much about it because he was eating hay and acting normal. He ate breakfast on Thursday but turn his nose up to his pm feeding. He hasn't been interested in his food since. He is eating hay and acting perfectly normal. I have tried changing buckets and I opened a different bag of pellets and he still isn't interested. He loves his hay and doesn't act like he has a sore mouth or jaw. He looks so good right now, I hope he starts eating soon. Has anyone out there ever had their babies go off their feed like that? I would like to worm him but I am afraid to until he starts eating good again.  Its a puzzle to me what is going on. Otherwise he is doing great. We are planning to wean him soon but again his lack of interest in his grain has me concerned about making that change in his life.

It could be that he just doesn't want the grain, but were he my foal, I would call the vet because something serious could be going on.

It is not uncommon for foals/weanlings to get ulcers.  I have had more than one breeder tell me that.  So it's possible he might be working on an ulcer.  An exam by the vet would confirm or deny that.

One of the M.O.'s with an ulcer is that the horse goes off its grain first.  Eventually off hay, then grass, ultimately eating nothing.

Again, I would call the vet for the little dollface

Sometimes they just get bored with their grain; you should see my horse eat his grain each day...talk about slow, and looking bored; somedays he won't even finish it.

 I wouldn't worry too much, especially if he looks fine and is eating other stuff; he is probably just filling up well enough on everything else and doesn't need the grain.

 If he hasn't been wormed, as well, I would highly recommend it; as he is at an age where he is highly susceptible. 

 Don't worry too much; as I said, he is probably just bored with the same old diet! He will eat it again when he is good and ready. Perhaps just offer it once a day? Or start stalling him at night? That way you can start the weaning transition as well, and it won't be like cutting him cold turkey from mom; stall her right next door.

My weanling did the same thing periodically.  Now that she's a yearling, she'll still sometimes not eat her breakfast but then she wolfs down her dinner.