HHW _ I do not draw a line between what is too intelligent and what is not to be fed live, (except when speaking of insects). It's not as humane as making sure the animal will not feel or know anything about what is coming to it. I don't think the suffering would be any worse for a dog or cat, except mentally (the intelligence we are speaking about) if the animal has come to know and trust humans. Many feeder rats have come to know and trust humans as well...
I do believe rats suffer, and they know that death is impending when they meet a snake... that's why they run and scream... I have (unfortuantely) fed a live rat to my snake once when no frozens were available and I was getting desparate for him. The rat knew the snake would kill it. It ran, screamed and even nipped at my snake in a attempt to stay alive. When it was all over (and I did not stay to watch) I swore never to feed live again, or at the very least, whack the rodent myself to spare its suffering. I felt a horrible, horrible guilt for a long time and cried a lot of tears for that one, single rat.
I know that in nature, none of the rats and mice eaten are humanely dispatched... but in circumstances where humans control the climate, movement and environment for our animals (both pets and feeders) we also take great steps to decrease suffering, to make ill animals well, and to end the lives of those suffering.
No animal should suffer, no matter what it's mental capacity is. No domestic animal should be euthanized because there is no home for it. I would never feed a live cat or dog, but I see no real difference between them and rodents...