Chrome is eating poisonous Red Maple leaves!!!!

I was taking pictures of Chrome because the fall colors are gorgeous!  Then I realized he was eating leaves.... from a red maple tree....  I'm so terrified he will get sick!  We put out a fresh bale of hay so that he will hopefully be too busy eating hay to eat leaves, but I don't know what to do.  I can't cut them down with leaves on them because they would be even more poisonous and I have no way to get all of the leaves picked up.  I don't have the materials to fence them off (there are six maples in the pasture fairly scattered apart) and I can't really afford to buy enough fencing to surround all of them.  Not to mention, look how close it is to the pond... I raked up as many of the leaves as I could and burned them, but look how many there still are to fall.....

I'm also confused because there have been horses on this property since 1991 and none of them have ever gotten sick or died... but I don't know if they ate the leaves.  What do I do?  I have no place to move him to.  Do I just keep tons of hay out and feed him beet pulp so that he stays so full of roughage that he doesn't want to eat them?  Continue to rake and burn them daily?  What about the stuff he's already eaten?

From what I've read it can take up to four days to shows signs of toxicity.  The signs are jaundice, lethargy, pale gums and dark urine.  There is no cure.  All the vet can do is give fluids and transfusions until the toxins pass and even that isn't always successful.  75% of horses who eat red maple leaves die.... even with immediate veterinarian treatment.  Also even if successfully treated most horses end up with laminitis too.

I feel like I'm going to puke.  Tell me I'm overreacting please.  I'm going to call the vet tomorrow and take the leaves to the extension office to professionally identify them.  Please pray that they are either not red maple or that he hasn't consumed enough to hurt him....

How is it I grew up on this property and always had horses and not a single one of them got sick when my pasture is covered in red maple and ragwort???  Over the course of twenty two years we've had eight horses, one donkey, several cows and tons of goats on this property, all of them lived here for at least a year, and none of them got sick... because of that fact my parents and husband think that there is nothing to worry about, but I can't help worrying.  I'm going to try to go to sleep.  Let me know if any of you have had any experience with maple trees.  Do your horses eat the leaves?  Have they gotten sick?

Edited to Add:  Okay I discussed it with my husband and explained to him that I was scared for Chrome's safety.  He suggested putting them in the round pen until the leaves have fallen and are no longer dangerous.  It shouldn't be any more than a month and some horses stand in stalls all year round.  I think being confined to a round pen is better than risking the danger of poisoning from the leaves.  Maybe I can get part of the pasture fenced off so he doesn't have to stay in there that long.  I'll just have to see, but for now I'm locking him up just to be on the safe side.  Please pray that the amount he has already consumed isn't enough to hurt him.  I'm optimistic that he hasn't eaten too many because there are still soooo many leaves on the trees and everything I've read says they have to eat several pounds worth of leaves to get sick.  Does anyone have any idea how many dry leaves it takes to make a pound?  I'll keep everyone posted.

Edited again to add:  Also while he's confined to the round pen I will be exercising him several times a day with hand walks on the roads and riding him around.  I will also probably turn him out in the pasture during the day, but only when I can supervise so I can chase him away from the maple trees.  Hopefully I realized all of this in time... or maybe they aren't poisonous...