To be halal certified the animal must be facing Mecca, have its throat cut while still alive and then ritually sacrificed by a Muslim who recites a prayer dedicating the slaughter to Allah. Because the animals must be slaughtered alive, stun guns are often not an option as they can kill an animal before the heart pumps out all the blood.
Kosher food complies with Jewish dietary law (kashrut), again governing what can and cannot be eaten by those practising the faith.
There are similarities in the method of slaughter in that both require use of a surgically sharp knife and specially-trained slaughtermen.
A number of supermarkets including Marks and Spencer, Tesco, Morrisons, and the Co-op all sell halal lamb. Some Waitrose lamb products are given a Halal blessing, but are not supplied separately and are therefore not considered halal on the shelves, the chain said.