The Pig is an Unclean Animal
Question :
Why was pork forbidden to the Muslim?
Answer:
The pig is an unclean animal; it lives in filth and it eats impure things, including human and animal excrement. This is acquired in its flesh, and the result of this is poor nutrition. Since this is its nature, there is no difference between those which are fed on blood and rubbish and those fed on other things.
Source:
Ibn Jibreen
Fatawa Islamiyah, Vol. 6 Page 242