Why is colistin used in the animal industry?

In this video, Dr. Sunil Gupta, Additional Director, NCDC, will talk on colistin which is commonly used in animal industry. He will discuss that the colistin is used on a large scale especially in poultry sector because the agriculturists feel that they can prevent any future infections in them and the size of poultry will be bigger. He will also tell us that this misperception among animal industry which is very wrong.