Question: Does kosher slaughtering cause animals to suffer?
Answer: Judaism has always respected the lives of animals, from the earliest code of the Ten Commandments until the present. From the sacrificial system observed during the time of the Temple, rules concerned with animal welfare developed. By the time of the Rabbis at least 2000 years ago, Jews took the lives of animals as humanely as possible and kosher slaughter was governed by the best science of the day.
During those 3000+ years, animals were slaughtered in the most inhumane ways by virtually every people on the face of the earth. Even today, people in many cultures treat animals in extremely inhumane ways.
As soon as modern science made us aware of problems with the traditional ways of slaughter, Jews began to alter the way they slaughtered animals. Traditional "hoisting and shackling" was replaced by a pen, even though it is a much slower procedure and increases the cost of kosher meat. In addition to being lifted up, a ritual slaughterer must move to the animal quickly, use a knife that is incredibly sharp and cannot have even the slightest nick, and then in a single motion cut through the trachea and esophagus, and at least one of these for fowl.
This leads us to an ultimate question: can we ever really ever kill a cow, goat, etc. without causing some pain and fear? Thus, Judaism has endorsed vegetarianism as a "higher" form of eating because it means not taking a life. For some it has meant not even eating an egg and others have made a distinction between a mammal and a fish. This often is a personal question, but overall it is a fact that Jews are concerned with animal rights and minimizing the pain and fear that results from slaughtering animals.
There are those who are actively seeking to end kosher slaughter (Schechita in Hebrew) as "inhumane." This appears to be just another form of anti-Semitism. If those fighting kosher slaughtering were sincere, why aren't they also fighting against fox hunts and bull fights?