Answer
Wa `alaykum as-salamu wa rahmatullahi wa barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
Dear questioner, thanks for your interesting question and we earnestly implore Allah to guide you to seek that which is lawful and stay clear of that which is prohibited.
Indeed, giving an animal a high voltage electric shock is a severe torture for it. However, if the electric charge is so low that it does not torment the animal, then it is all right to use it.
If the animal is still alive after the electric shock, it can be slaughtered and eaten. But if it dies from the shock and then has the throat slit, it is impermissible to eat it.
In this context, we would like to quote this fatwa issued by the Islamic Fiqh Council affiliated to the Muslim World League,
At the tenth session of the Islamic Fiqh Council at the Muslim World League held in Makkah from Saturday, 24 Safar 1408 A.H./ 17 October 1987 to Wednesday, 28 Safar 1408 A.H./21 October 1987, the issue of slaughtering animals by means of electric shock was considered. After thorough discussion of the issue, the Council agreed on the following:
First, if the animal is still alive after electric shock and then it gets slaughtered, it is thus slaughtered in an Islamic way and there is nothing wrong in eating it. Allah Almighty says, “Forbidden unto you (for food) are carrion and blood and swine flesh, and that which hath been dedicated unto any other than Allah, and the strangled, and the dead through beating, and the dead through falling from a height, and that which hath been killed by (the goring of) horns, and the devoured of wild beasts.” (Al-Ma’idah 5:3)
Second, if the animal happens to die through the electric shock before it gets slaughtered, then it is carrion, which is forbidden for Muslims to eat. Allah Almighty says, “Forbidden unto you (for food) are carrion…” (Al-Ma’idah 5:3)
Third, giving the animal high voltage electric current before slaughtering is, in fact, severe torture for the animal. Islam prohibits torture and enjoins mercy and clemency. The Prophet (peace and blessings be upon him) 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.” (Muslim)
Fourth, if the animal is exposed to a low electric current that would not cause the animal to suffer, and it is rather undertaken to relieve the animal’s pain and control it while slaughtering it, then it is legally all right to do so, for so long as it is in people’s favor.
Allah Almighty knows best.