This was in the New York Times in January:
"With the start of the new year, Belgium became the latest European country to ban traditional Jewish and Muslim animal slaughtering practices. The move was applauded by animal rights activists but condemned by religious leaders who see the ban as a threat to their communities.
"At issue is whether to allow religious exemptions to European Union rules that state animals must be knocked out before they are slaughtered, which supporters say is more humane. The United States has similar regulations, but allows for religious exemptions.
"Both faiths require that the animal be treated well in life and be healthy and unharmed before slaughter, which all Jewish religious authorities and some Muslim ones interpret as a prohibition of “stunning” before slaughter.
"Religious leaders say minimizing an animal’s pain has always been central to their traditions, and a ritual slaughter — carried out with a sharp blade to the neck — should be quick and almost painless.
"When they are stunned, animals are rendered unconscious through blunt force, electric shocks, gassing or a steel bolt that penetrates an animal’s skull.....
"But kosher-certifying authorities say that no form of stunning before slaughter is permissible, said Rabbi Menachem Genack, who oversees certification for the Orthodox Union, the world’s largest kosher certifier. Some halal-certifying bodies agree, but others do allow nonpenetrative stunning before slaughter."
So, in fact, animals slaughtered under halal rules can be stunned (though not by means of a bolt) but kosher rules prohibit any form of stunning.
Let's face it, any method of slaughter is pretty horrible so perhaps more emphasis should be placed on how an animal lives rather than on how it dies. Providing more natural living conditions throughout life would be much more expensive than intensive factory farming methods so I wonder how many meat eaters would be as prepared to campaign for these sorts of changes, which will undoubtedly hit their pockets.