534

Obviously, it is less than 1000.
Hence, the path can be divided into 3 phases
3000--2001, 2000-1001, 1000--
On the first phase, the donkey moves 1000/5=200km,
on the second phase, the donkey moves 1000/3km.
Thus, the last phase, the donkey moves 1000-(200+1000/3). Hence, it eats 466.6 = 466.
Thus, 1000-466=534.