It’s not unreasonable to assume that if a nervous system is present and similar pain signals are send, similar suffering is experienced by animals as humans. Simply because suffering is a motivation to take action. There might be a difference in that most animals, like baby’s, wont be able to seperate themselves from their suffering/pain. I am suffering vs suffering is all there is. If thats the case, pain for animals might even be worse then humans. That might be backed up by the fact that most animals are very pain avoidant (makes them really scared), where some humans seek it out, and most of us are able to accept a bit of pain to get something better. (There seems to be some indication that other animals have a sense of self, like dolphins, certain birds, elephants etc) (Also seems that pain for animals, same as with humans, is not felt when they are filled with adrenaline and in fight mode)