I guess I've been lucky then as I have fed all my horses Garlic for years n years and have never had a problem w anemia...ever
Granted if I gave them a cup of garlic daily sure maybe they may develop it, but at 1 tablespoon/day from May-oct (our bug season) I'm not concerned.
I've read the articles, I've talked w my vet, and He isn't concerned as the amount and type He feels is quite safe, and from what I've read neither am I concerned.
So to the OP if you want to give your horse garlic ensure its the granulated garlic, and I give 1 tablespoon a day in their grain. I find it does make a difference
Horses are like chips...you can never just have one