Ritual slaughter is the practice of killing animals using methods prescribed in scripture for the purposes of eating. Many holy books demand that all animals that are eaten by believers must be ritually slaughtered using specific procedures. These practices are controversial because the animals are usually not stunned before slaughter, which raises animal welfare concerns.
Ritually slaughtering meat to Islamic requirements is referred to as Halal and to Jewish requirements as Kosher. Ritual slaughter usually involves draining the blood from the animal. Sikhs and Hindus are forbidden from eating ritually slaughtered (Kutha) meat. Christians are generally allowed to eat any meat, ritually slaughtered or not.
Some countries regulate religious slaughter, and various bans have been imposed, only to be overturned later. Denmark recently banned ritual slaughter of animals.  Switzerland has had a ban on non-stun ritual slaughter since 1893, Sweden since 1937.  Some countries mandate that an animal must be stunned immediately after being cut.
Ritual slaughter in religion
Jewish law prohibits eating animals that have died from natural causes or have suffered from disease. An animal must be slaughtered by a single cut in a specified location across the throat. This task should be undertaken by a Jew. Slaughtered meat must be drained of blood to be considered acceptable. This usually involves soaking the carcass in water to open the pores, then extracting the blood using salt. This process is called Melihah.
Stunning the animal before slaughter is considered a type of injury which makes the meat not kosher.  This puts the animal though unnecessary suffering. In the UK, only a tiny minority of animals are stunned before kosher slaughter. 
In addition, Jews may not eat hare, hyrax, camel, pig, birds of prey and bats.
"This day [all] good foods have been made lawful, and the food of those who were given the Scripture is lawful for you and your food is lawful for them."
In the UK, 80-90% of animals are stunned before slaughter for halal purposes.  Muslims are also forbidden from consuming pork, blood, animals with canine teeth or fangs, birds with talons or alcohol.
Christianity does not call for the practice of ritual slaughter. However, there is some controversy over the consumption of halal meat by Christians in Corinth nearly two thousand years ago, as this was regarded as meat sacrificed to a false god or "idol". Acts 15:29 says it is not allowed, but Paul's letter 1 Corinthians 8:4 says it is acceptable. This may have been a local (arbitrary) dispensation because of the difficulty of obtaining non-ritually slaughtered meat in Corinth at the time. 
Jehovah's Witnesses are forbidden from consuming blood. They insist that the blood be allowed to drain from slaughtered animals, but do not require the blood to be extracted. Most commercially slaughtered meat fits this requirement, so believers are not generally considered to have extraordinary dietary requirements.
Many countries require that animals must be stunned, either electrically or concussively, before slaughter. Ritual slaughter typically requires the animal to be conscious during slaughter. John Blackwell of the British Veterinary Association claimed that allowing an animal to bleed to death causes unnecessary suffering:
- "They will feel the cut. They will feel the massive injury of the tissues of the neck. [...] They will perceive the aspiration of blood they will breathe in before they lose consciousness. [...] People say we are trying to focus on the last five or six seconds of an animal’s life when it could be 18 months old. It’s five or six seconds too long. "
The tabloid press has framed the issue as though there was a conspiracy to secretly introduce ritually slaughtered meat.  This reaction verges on Islamophobia.  However, they also raise the animal welfare issue.
Apologists resist ban
Apologists have claimed that their religious freedom would be infringed by a ban. They claim the animals quickly expire; The method is comparable with stunning the animal first, which is itself not always successful:
- "Secular efforts to mitigate the suffering of animals when taking their lives for food should not be made at the expense of denying religious people the freedom to do so in their own way. [...] The kosher and halal methods of slaughter with an extremely sharp knife cause a rapid loss of consciousness which is indeed equivalent to the stunning of the animal. [...] Targeting specific religious communities is not helpful and misses the very point that such a discussion should be addressing. "
- ↑ 
- ↑ 
- ↑ 
- ↑ 4.0 4.1 
- ↑ 
- ↑ 
- ↑ 
- ↑ 
- ↑ Religious slaughter
- ↑ 
- ↑ 
- ↑ 
- ↑ 
- UK National Secular Society, Religious non-stun slaughter of animals