Extinct

What would happen if the primary consumers ,in the food web diagram, became extinct? The primary consumer in our food web is the horse. If all horses became extinct, the cougar would have nothing to eat. If the cougar had nothing to eat, it would die very quickly, because they have no food. Not only would the cougars die, but the other carnivores such as, lions, tigers,etc.,who eat horses, would die too. If many carnivores died, the scavengers and decomposers would finish them off. This would lead to extinction to other animals, too.