The Sonepur Mela of Bihar is organized every year in the Hindu month of Kartik (November). The mela (fair) is held on the embankment of River Ganga at Sonepur.
They call this the worlds largest cattle fair and for the amount of people that may be true, but sadly there really are not that many animals. I would have to guess 50 elephants, 60 cattle, 400 horses, 300 goats and a few other types of animals