Consciousness is the real enemy. Animals are suffering too, but they are not aware of it. Also, they will never complain about the futility of their lifes, because they don't know that their life is pointless. If an individual isn't aware of its own mortality and futility, it can not suffer from that knowledge. Of course the physical pains of life will also exist without consciousness. But they are accepted, without questioning it, by an unaware individual. Furthermore, animals are living solely in the present moment (at least to a large extent), so fear of future pain and actual memory of past pain are also not bothering them.
Conclusion: No consciousness = no awareness of futility/pain = no problem.