Animals feature in some works on universalism but not many. However, they do give rise to some important and quite challenging questions.
To start with, do we know which animals, if any, are conscious? And, if consciousness is an attribute of the soul, does that not mean that animals have souls? If so, what will happen to their souls after death?
Leading on from this, if we conclude that some animals are conscious, but they don't have a future beyond this life, should we not ask why God did not design them to be unconscious biological machines instead? If animals' suffering does not lead to a good afterlife, would not doing that make God the cause of unnecessary suffering?
I think it is surely the ambition of God to restore all creation to a positive state, the bible often speaks of the reconciliation of all in heaven and on earth and the making of all things new, he is clearly aware of the needs of all creatures and capable of satisfying them all, so I cannot envision an outcome where God provides anything short of that for every sentient individual ultimately.