Apart from cognitive skills, an important factor is the capacity of suffering. So even dumb animals might be able to feel intense pain.

In humans, while forms of suffering like loneliness, depression can be bad, pure physical pain can itself a terrible thing. For instance severe torture for 10 minutes can be worse than months of depression.

Now even if cognitive aspects are diminished in animals, the physical senses are active and often much more sharp(birds eye sight, dogs hearing).

So, what we can do is independent of whether we are eating animals or not, is to recognize this fact that animals can suffer, and ensure that factory farms which deal with billions of animals atleast stop some of the more terrible forms of animal cruelty (dunking birds in hot water while still alive).