tail and mane hair losses are indicatons of allergies, if worms are not detected, or fence rubbing going on (which also sometimes allergy caused).
my horse Nashville had a multiple of allergies, and which the country vets at that time had no idea what was going on with him. but he lost all the hair at the top of the tail at the butt and it looked really funny being bald top and hair bottom tail.
what I had to do was get a allergy blood panel, and identify the allergies, then the specialized vet had the anti-immune vaccines made from his blood. we did these injections for 3 years and now my boy has a beautiful tail again, and a awesome shine coat all the time. no more shots and no more allergies.
with smart pak we had to supplement various minerals, or vitamins to help the immune systems and the vaccines, as with allergies there is a lot of nutritional losses with the poor horse having to fight the allergies off. so the smart pak vitamins and supplements have been a blessing in keeping my boy healthy all the way around.
the first photo is after 3 years of dealing with and treating allergies, the 2nd photo is when the allergies were at the worst. but the first sign before the allergy break out was the tail hair losses, then the mane hair losses, and even some hoof problems.
"There's a difference between interest and commitment. When you're interested in doing something, you do it only when it's convenient. When you're committed to something, you accept no excuses; only results." - Kenneth Blanchard