A cat or dog can experience agony just as thoroughly as a human can. And it tends to have very similar psychological effects if the animal survives: anti-social behavior within its own species, severe aggression and/or fear, and very easily startled into expressing aggression/fear, just like humans with PTSD.
I do not believe animals feel pain. I do not believe they are conscious. I believe they are little (or sometimes big) natural creatures with a brain that is a shadow of the human brain but, even more so, without the ability to interpret their surroundings with the same awareness of man, who was designed “in Gods image”, which animals were not.
Animals are “meat on the hoof”, which require no refrigeration as long as they are kept functioning. As a bonus, they also serve the same purpose for adults and children that a teddy bear serves for small children. If my wife dies before me, I will get a Golden Retriever and name him Chester. I will not get him “fixed”.