What kind of treatments do you know to get the tail of a horse white again?
If I wash it only with (horse) shampoo it just gets lighter but never really white as it should be. There is always a yellowish color there, expecially at the hair-ends.
I also tried lemon juice, but that won't work either...
Just so you know, I don't wash the tail of my horse every day, but rather when it is warm outside and I would wash him anyway.
I use 'White-n-Bright', but you can find several products like it. It's a purple liquid the consistency of shampoo. I'm sure it's similar to laundry bluing, but I've never had it turn my horse blue, like was mentioned above. You put a squirt in the wash water, but for stains like you're talking about, I squirt the concentrated liquid on those spots. Get a rubber curry comb to work it in. On the tail, I put a little on the length of the tail, then rub it against itself to work it in. I let it sit, rinse it out, and repeat if necessary. You will eventually get it blindingly white.
Usually this is staining. You can prevent staining by using a silicone hair treatment.
Once it's there you can try whitening shampoos or adding a few drops of laundry bluing to the rinse water. Note: if you add too much, yes, you will turn your horse blue. http://mrsstewart.com/wp/wp-content/uploads/2013/02/All-About-Bluing.pdf
I've used Bon Ami (don't substitute another brand, this one is non-irritating) to get grass and manure stains off of white stockings with good results and it should work on tail hair as well.
I use a product called "White N Bright". I would make sure to work the shampoo deep into the tail and let it sit for 5 minutes before rinsing. You may still have yellowing in the tail from stains.
The other option, which works but most people won't like this, is diluted bleach in water. Use only a capful for a gallon and soak your horses tail from the dock down (don't get on skin!). Soak for a minute, let sit for 3 minutes and then rinse thoroughly. You may want to use gloves if you go this route.
