Faizan, it is considered to be painful to the animal. Guru Nanak condemns it somewhere in Asa di War. Its been reinforced by the rehit. Newer forms of torture and pain are quite simply, not reconciled.
For a 'modern' understanding, from the almighty wikipedia:
Halal food and animal welfare
The ritual method of slaughter as practiced in Islam and Judaism has been decried as inhumane by animal welfare organisations in the UK who have stated that it "causes severe suffering to animals."[11][12]
However, in 1978, a study incorporating EEG (electroencephalograph) with electrodes surgically implanted on the skull of 17 sheep and 15 calves, and conducted by Wilhelm Schulze et al. at the University of Veterinary Medicine in Germany concluded that "the slaughter in the form of a ritual cut is, if carried out properly, painless in sheep and calves according to EEG recordings and the missing defensive actions" (of the animals) and that "For sheep, there were in part severe reactions both in bloodletting cut and the pain stimuli" when Captive Bolt Stunning (CBS) was used.[13] This study is cited by the German Constitutional Court in its permitting of dhabiha slaughtering.[14]
In 2003, an independent advisory group - the Farm Animal Welfare Council (FAWC) - concluded that the way halal and Kosher meat is produced causes severe suffering to animals and should be banned immediately. FAWC argued that cattle required up to two minutes to bleed to death when such means are employed. The Chairperson of FAWC at the time, Judy MacArthur Clark, added, "this is a major incision into the animal and to say that it doesn't suffer is quite ridiculous."
Halal and kosher butchers deny their method of killing animals is cruel and expressed anger over the FAWC recommendation [12].
Majid Katme of the Muslim Council of Britain also disagreed, stating that "it's a sudden and quick haemorrhage. A quick loss of blood pressure and the brain is instantaneously starved of blood and there is no time to start feeling any pain."[12]
In April 2008, the Food and Farming minister in the UK, Lord Rooker, stated that Halal and kosher meat should be labelled when it is put on sale, so that the public can decide whether or not they want to buy food from animals that have bled to death. He was quoted as saying, "I object to the method of slaughter ... my choice as a customer is that I would want to buy meat that has been looked after and slaughtered in the most humane way possible.". The RSPCA supported Lord Rooker's views. [15]
For the Food and Agriculture Organization of the United Nations and the Humane Society International, "the animals that are slaughtered according to Kosher and Halal should be securely restrained, particularly the head and neck, before cutting the throat" as "movements (during slaughter) results in a poor cut, bad bleeding, slow loss of consciousness if at all and pain." [16]
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