The voyages of Columbus initiated a cultural and commodity exchange that was unique in the history of the world. Two different worlds, that were previously unaware of one another, collided and much was exchanged between the two. Europe came to be known as the Old World and America was dubbed the New World. The introduction of Old World animals to the New World had a dramatic impact. On Columbus' second voyage, he brought many new animals with him. These animals included horse, cattle, sheep, goats, and pigs. Of those animals, the horse had the greatest impact on transportation, labor, and warfare. Pigs were important as a food source and sheep were utilized for wool. Other beasts of burden like mules and oxen would make their way to the New World, but did not have the same impact as the horse. Explorers also brought the black rat with them by accident, which had the negative effects that you could imagine, including the transmission of disease.
The exchange of animals from the New World to Europe did not have the dramatic impact you would expect. Turkeys were the animal that had the greatest usage as a food source. Llama, alpacas, and guinea pigs were also brought back to Europe.