I was asked this question in my shiur by people who have medical knowledge.I always understood the gemarah that the severing of the two simonim renders the animal painlessly dead? Also there would be no blood unless juglar vein cut whitch is not required for an animal. can you help?
I do not know if Shechitah is painless and to the best of my knowledge the Gemara does not discuss the issue anywhere. However, when a person cuts himself with a sharp knife it is usually not painful at first, and the animal is certainly not in a position to feel pain for very long after Shechitah. The Farm Animal Welfare Council (the UK Government's independent advisory body) discovered that sheep loose conciousness after between five and seven seconds. Larger animals stay conscious for longer (up to two minutes). Others have disputed these findings, and have claimed that animals loose consciousness even more quickly. (The Farm Animal Welfare Council has been accused of not providing scientific evidence for its findings and indeed the Government of the UK has chosen to ignore its previous recomendations on Shechitah.) In any event the animal is considered to be alive after Shechitah (see Chulin 30a and 33a).
From the Shechitos that I have witnessed, I can tell you that there certainly is blood. The Gemara (Chullin 27a) says that in Shechitas Kodshim we must have Dam ha'Nefesh for Zerikah. Normal Shechitah does cut the jugular veins, as well as the carotid arteries. Obviously, a Shechitah does not need to cut more than the majority of the two Simonim.
Dov Freedman