Question

How can 50 cows be tied on 9 pillars with an odd number on each pillar?

Answer 1

It is impossible to do this. 

We need, x1 + x2 + x3 + ... + x9 = 50 where x is the number of cows on each pillar and must be odd. 

So, 
x1= 2*y1 + 1
x2=2*y2 + 1 and so on

Thus substituting these values, in above euqation, we get
2 * (y1+y2+y3+y4+y5+y6+y7+y8+y9+9)= 50
2 * (y1+y2+y3+y4+y5+y6+y7+y8+y9)=41
y1+...+y9 = 41/2. 

Since we cannot cut cows in half, this number needs to be integar. Thus it's not possible. 

Answer 2

If the question is rigid by the requirement of odd number condition, then the solution is non-existant.

If the question can be altered a bit, then one can tie one of the cows to 2 pillars and get the result ultimately but it will be an act of animal cruelty and it is a punishable offence in India.