Don't brush it and wash it every once and a while and sometimes a tail bag can help
Cocosoya high in fat and will help coat and hair both
I moved and switched hay suppliers. That's been the best thing for my mares' manes and tails, good quality hay. Even biotin doesn't make as big a difference.
Mtg works well but if you wanna go all out try biomane! Works so so so amazing
This sounds really stupid but my farrier suggested it to me 😂 Rub Kevin Bacons hood supplement into the area needed once a week and believe it or not it helps grow back the hair ☺️
Rubbing coconut oil into the mane plus tail then braiding it for a couple day then wash it out and repeat
My horse use to have a very thin tail when I first got her :( so I just shampooed it about every other week and put conditioner in it every other day and now her tail is fuller :)