Pigs eat grass if they are very hungry, but they can't use it as a regular source of food.
Here you do have forests, where pigs could be raised by letting them root about in the forests for a good part of the year. Therefore, you have a different attitude toward them compared with what continues to exist in the Middle East.
Pigs prefer to wallow in clean mud, but if nothing else is available, they will frequently wallow in their own urine, giving rise to the notion that they are dirty animals.