When you slit their throat, if you do it right, they are said to loss consciousness within 5 seconds, and the bleeding is painless, the only pain being the puncture wound. The resulting convulsions are due to the electrolyte imbalance in the muscles as they blood drains from the body. I actually had a friend, a bison and sheep rancher I witnessed kill animals this way, end up accidentally taking his own life while whittling a bone ornament on his leg. His knife slipped and sliced his leg, puncturing the femoral artery, he had just enough time to walk to his bathroom, sit down and reach for his first aid kit. He died smiling.