Why is the front portion of a cow considered kosher?

Answer 1

Cows are by nature kosher because they chew their cud and have cloven hooves. Front or back is no issue, but how the cow is killed does affect whether its meat is considered kosher - the idea is to drain the life blood out of the meat in the killing process (in ancient times thought to be both relatively more "humane" than clubbing an animal to death and the proscription was against eating blood although people didn't realize it was infused into the flesh...). If on the other hand you're referring to the idea that the proscription is not to "seethe" (boil, simmer, cook...) a calf in its mother's milk and the milk comes from the udders in the posterior of the cow, that's a different issue. There it is a question of respect for the animal since mother's milk is life-giving and it seemed to be just a violation of the value of life and motherhood (among other things). That's why dishes like Beef Stroganoff are not kosher, because the sauce over the beef contains milk products.

Answer 2

The lower part of a cow - and other domestic animals (note that the following laws do not apply to wild animals such as deer) - can be kosher, but only when prepared in strict accordance with shechita, the laws regarding animal slaughter. During a process known as porging, certain fats known as chelev and the sciatic nerve, known as gid hanasheh, must be removed from the carcass as these parts are treif - that is, not kosher, and as such cannot be eaten by observant Jews. Removing them is a labour-intensive and very complicated task that requires a highly-trained shochet (slaughterer/butcher) - to be kosher, all meat must have been slaughtered by a shochet, but most do not have the training to prepare the hind end of the animal. For this reason, it makes more economic sense to sell the hind quarters to a non-Jewish butcher for preparation and sale to gentiles (non-Jews).