Islamic scriptures are generally the Quran and the canons of Ahadith and as such one does not find in them minute details of the procedure for slaughter. Indeed, in the Quran, except for ablution you hardly find a delineation of how to perform something, not even the mandatory Salat. Much of the Prophetic religious wisdom was based on the acceptance and perpetuation of cultural norms - without codification. Of the various ways of killing animals those considered un-Islamic were explicitly prohibited, for example:
Forbidden to you are carrion, blood, the flesh of swine, the animal
slaughtered in any name other than Allah's, the animal which has
either been strangled, killed by blows, has died of a fall, by goring
or that devoured by a beast of prey - unless it be that which you
yourselves might have slaughtered while it was still alive - and that
which was slaughtered at the altars. - You are also forbidden to seek
knowledge of your fate by divining arrows ... (5:3)
The Prophet (puh) witnessed and practiced slaughter himself and even improved it.
Two are the things which I remember Allah's Messenger (puh) having said:
Verily Allah has enjoined goodness to everything; so when you kill,
kill in a good way and when you slaughter, slaughter in a good way. So
every one of you should sharpen his knife, and let the slaughtered
animal die comfortably.
The initial few generations of Muslims relied heavily on lore and oral tradition a fact that often goes unappreciated and unnoticed. They didn't feel the need to document how to "change clothes," "dig graves," or "slaughter animals." It was only after formal codification of the customs and precepts of the Sharia, and the collection of Hadith and Akhbaar, started due to natural requirements of an expanding empire, wherein the Arabs (and their customs) were rather a minority that one finds attention to details in expositions of rituals and customs.
One does see wisdom in Divine Silence on gory details that allows flexibility with human progress.
On Stunning
In the 1960s, AI-Azhar jurists were presented with the question
of whether stunning livestock prior to slaughter was acceptable under Islamic law. The unanimous verdict (Fatwa) was:
"Muslim countries, by approving the modern method of slaughtering,
have no religious objection in their way. This is lawful as long as
the new means are 'shar' (Ahadd) and clean and do 'cause bleeding'
(Museelah al-damm). If new means of slaughtering are more quick and
sharp, their employment is a more desirable thing. It comes under the
saying of the Prophet(s) 'God has ordered us to be kind to everything'
(Inna'l-laha Kataba-'l-ihsan 'ala kulle Shay'in)." (The History of
Azhar, Cairo; 1964; pp. 361-363)." (Source)
That said, however, as Richard Foltz notes: "They apparently did not consider the unreliability of stunning, the assembly-line conditions normally associated with the use of stunners, nor any other aspect of the issue."
The issue goes much deeper, as even though the scriptures don't detail how to slaughter they do in a very clear manner elevate non-human animals to the status of persons with intellect and emotions. If the Chapter "The Ant" exposes the inductive and deductive argumentation capabilities of an ant, the Prophet (puh) compliments the person-hood of animals by exposing the emotional component of their existence. When he saw a man sharpening his knife while an animal waited nearby, he reprimanded him, "Do you wish to slaughter this animal twice, once by sharpening your blade in front of it and another time by cutting its throat?" He even forbade killing the offspring on an animal in front of its mother.
Muslims have failed to uphold the precedents themselves; the annual shared-ritual sacrifices are blatant disrespect of the Prophetic injunctions of not killing the animal emotionally before physically. Muslims intellectuals became too infatuated with Aristotle to not see the "rational ant," and the Jurists became too anthropocentric to not include "alleviating suffering," in principles of Sharia (Maqasid-al-Shariah). Whereas stunning, in factory settings, attempts to alleviate the "physical" pain of the non-human animals, it apparently does increase the "emotional" suffering. Uncritical acceptance of stunning would only add insult to injury.
