What do I do for my horse to have a healthier mane and tail?

I have a 5 year old Thoroughbred but he has the thick mane and long tail of a pony. Whenever I pull his mane or brush his tail a lot of hair comes out, just handfuls of it. The only reason he isn't bald is because he has so much of it and it's so thick. What are some home remedies and products I could try to give him a healthier mane and tail? I currently have him on a daily vitamin and a rice bran mix but it's just not enough.