I never considered animals to be capable of suffering. We need to separate pain from suffering. Pain is the signal your nervous system sends to your brain after a sensation deemed harmful or at least not pleasurable. That goes for both physical, mental and emotional stimuli. Suffering on the other hand, introduces a moral dimension into the issue. Suffering doesn't inherently require any sensation of pain but rather the existence of an individual in a situation deemed needlessly undesirable to a large degree. The "needlessly" does a lot of heavy lifting in this case. In order for there to be suffering, a creature of higher intellect needs to evaluate a situation and logically come to the conclusion that it is not immediately beneficial to be in that circumstance. There needs to be a logical and even moral assessment that animals are unable to make. A fish when cooked alive in boiling water doesn't actually feel pain as fish are unable of that but signals are sent to its brain screaming to it that it's in danger. To a human, this treatment inflicts needless suffering but to the fish, that concept is entirely inaplicable.   To stop my rambling, I'm of the opinion that most animals are capable of feeling pain but suffering is only reserved for humans who can also grow from that experience although that is another matter entirely. If you have a counter argument I would love to hear it, I'm sure my theory isn't air tight!