Why is the back of a cow not kosher?

Answer 1

It can be kosher, but only when the chelev(certain fats) and gid hanasheh (sciatic nerve) are removed. Removing these parts is a very highly-skilled and labour-intensive process requiring a shochet (Jewish slaughterman) or butcher even more highly trained that they need to be in order to produce any kosher meat at all. As a result, the front part of the animal is usually used for kosher meat and the hind part sold to non-Jewish companies for the production of non-kosher meat. In Israel and other areas with a limited market for non-kosher meat, this would obviously be wasteful and so all shochtim (plural of shochet) and butchers must complete further training.

Answer 2

The question of what foods are Kosher and what foods aren't comes down to when The Bible was first being written. The Hebrew leaders back then made the decisions as to what Jews should or should not eat. There is some scientific reasoning behind some of the rules, like, for example; pork, if not cooked properly can make you sick because of Trichinosis worms that live in the meat. Telling people not to eat pork will make sure no one gets sick because some may not cook it properly. Other examples are simply based on whether or not a Rabbi blesses a food. Some water and soft drink companies have Rabbis come into the plants and bless the vats.

Kosher animals have split hooves and chew their own cud. Pigs do not chew their own cud.

Kosher food has nothing to do with blessing the food. the mashgiach (kosher supervisor and doesnt have to be a rabbi, makes sure that non kosher substances don't go near the kosher food.