You're losing track of your arguments. Animals have the capacity to suffer independent of human existence, human concepts. The central dispute involves the moral relevance of this suffering. Your position appears to lead you in absurd territory: an infant's suffering is insignificant because her actions are based on instinct.
Not directed at me, but to this my answer is very simple, direct, and blunt.
If suffering is inherently wrong in all cases, we do an injustice to ourselves every time we lift weights or perform a job which is physically difficult. The premise that suffering is inherently wrong is inherently wrong... and a gross generalization which is not warranted.
Neither is causing the suffering of another creature inherently wrong. It depends on the circumstance and the intent. Self defense would be one circumstance in which violence is justified... even against other humans. To eat that which our bodies are designed to process seems to me to be a fair intent, as well. Certainly, suffering should be minimized to the extent that is possible in achieving the desired result... but the need itself and the pursuit of it is certainly justified. There are some things I will accept as absolutes, but this I will not. Back to self defense: Allowing someone to rape or kill you when it is possible to physically prevent it by violence enables it to continue against others. Standing there and watching someone else do such to another, out of an aversion to violently preventing it is also morally reprehensable... given that you are capable of preventing it. The question as applied to the O.P. is only a question of where to draw the line... absolutism cannot ethically be applied. Please specify and justify the place in which YOU draw the line, that I might reply to it.
Please note that if you apply my own analogy here to giving animals rights equal to humans, then your moral stance would require you to defend them violently, as well... if you agree with my assertion of its legitimacy in defense.
(added) err... I misread Cain's intent and actually extended his remarks (a mistake of context, due to scanning instead of reading). I suppose that makes my post directed at Cyborg, instead of Cain. I'm still a bit cofused as to the participants, as I've been away a while.