How is that in anyway comparable to the suffering of an actual animal?
But yes, the relevance of suffering seems proportional to relatedness with the sufferer. Or maybe the ability to identify with the sufferer, based on perceived intelligence and self-awareness.
It's also not so black or white. Does a cow have greater "capacity for suffering" than an oyster? Does this have ethical consequences? I think it does.
And yes, maybe oysters are closer to plants than cows, in that regard.
But it's not just about suffering. It's about the morality of killing other lifeforms. Personally, I'm OK with it. I'll be eaten after I die. Indeed, I'm always under attack from bacteria, yeast, molds, etc. But I won't eat anything that I wouldn't kill myself.
Have you actually, personally, killed a cow, chicken, or pig?
Granted, the fauna in question aren't living on the farm, but that's a distinction without a difference.