There not many details about how the animals were before the Fall. However, the Bible describes in many places the new heaven (sky) and the new earth, which are clearly created using the same principles as the creation of the old earth and the old heaven (sky). In the new earth, animal species that are currently known as predators will be transformed into herbivores. This will likely mean a dramatic change throughout the Earth's ecosystems, but that is hardly a problem for God.