The animations were improved and now the length of the mane/tail depends on the breed of the horse.
Right now there are 4 lengths: regular (the old manes), short, medium and long.
Certain breeds also get a braided mane. (so far Andalusian, Friesian, Lusitano, Pegasus, Unipeg, Charger, Winged Charger, Magic Charger, Magic Pony, Ponycorn, Ponypeg, Magic Zebra, Thestral, Phestral )
Some breeds get one type, some breeds get more possible types.
The new manes/tails will only appear on the 'new' horses.