There is some uncertainty about the continuum of animal cognition and how it relates to their capacity to suffer.
Having a small uncertainty about animal suffering and then saying that because of the large number of animals we eat, even a small uncertainty is enough to make eating animals bad, is a variation on Pascal's Mugging.
Yeah, this is why I used the number '1-in-20'. It's somewhat arbitrary, but it serves the function of ruling out Pascal-level uncertainty.
I'm currently unconvinced either way on this matter. However, enough arguments have been raised that I think this is worth the time of every reader to think a good deal about.
http://nothingismere.com/2014/11/12/inhuman-altruism-inferential-gap-or-motivational-gap/