2 days after people; There are nine million dairy cows in the United States. They were milked twice a day. The cattle are now confused because they are now longer on their daily milking schedule. Some cattle develop infections of the udder and die but most stop lactating and dry up. The cows in most danger are the baby calves because they had to be hand fed by people. Cows that are unable to escape their pens will starve to death.
30 years after people, Most cattle have died out because of predators and the fact that they struggled to give birth without human assistance. Those that managed to mate and reproduce successfully now graze on the Colorado Plains. They have begun to return to the wild.
150 years after people, Cattle still survive on the Colorado Prairie but they now share the prairie with Bison.