All perfect praise be to Allah, The Lord of The Worlds, and may His blessings and peace be upon our Prophet Mohammad and upon all his family and companions.
In Sharia terms, lawful meat is that of the animal slaughtered in due form, as clarified in the following verse where Allah, The Almighty, says: " unless ye are able to slaughter it (in due form)" {Al-Ma`idah/3}. Slaughtering in due form means cutting off the animal`s throat, but if it died or showed no sign of life before cutting its throat, then it is considered dead meat which is unlawful to be eaten, as clarified by An-Nawawi, a Shafii scholar, who said: "Cutting off the throat is a condition for the due form of slaughter, and it is the correct Madhah (School of thought)…Our fellow scholars said: "If part of the throat was left uncut, and the animal died, then it is dead meat." {Al-Majmou`, 9/86}.
Islam forbids all forms of torture whether upon slaughtering the animal, before it, or after it, prior to releasing its last breath. This is included in the Hadith of the Prophet (PBUH) who said: " Verily Allah has prescribed ihsan (proficiency, perfection) in all things. So if you kill then kill well; and if you slaughter, then slaughter well. Let each one of you sharpen his blade and let him spare suffering to the animal he slaughters.” [Muslim].
Prophet Mohammad (PBUH) forbade all forms of torture exercised by some butchers, such as dragging the animal by its ear, slaughtering it with a dull knife, or cutting its meat before releasing its last breath. It was narrated that Abu Sa’eed Al-Khudri said: “ The Prophet (PBUH) passed by a man who was dragging a sheep by its ear. He said: ‘Leave its ear alone and hold it by the sides of its neck.’”{Ibn Majah}.
It was narrated that ‘Abdullah bin ‘Umar said: “The Messenger of Allah (PBUH) commanded that the blade should be sharpened, and hidden from the animals, and he said: ‘When one of you slaughters, let him do it quickly." {Ibn Majah}. The aforementioned Prophetic narrations give examples that are inclusive of all forms of torture regardless of difference in time and place.
Moreover, it is worth mentioning that some forms of torture could render the animal invalid as an Udhiyah or Aqiqa... etcetera. This happens when it is choked to death, thrown from a high place, shot, or one of its organs is cut off, like its ears.
In conclusion, we advise butchers to fear Allah, and be as merciful to animals as possible. And Allah knows best.