If a horse gets his tail chewed off how long will it take to grow back?

Like people, the growth period for horse's manes and tails varies between individuals and breeds.

Some horses, (like many of the old style Appaloosa horses) have very thin short manes and tails. Some to the point where the longest hair isn't even 2 inches long.

Other breeds are noted for their thick manes and tails (Andalusians, Friesians, Arabians are examples).

Some horses have tails that touch the ground or are even long enough to drag.

Left in it's natural state the hair on a horse's tail would be worn down as it touched the ground...but generally the length stops short of ground level by several inches unless the owner braids, conditions or even puts the tail in a tail bag.