Returning to the Iberian Peninsula, this chapter considers how colonial experiences influenced early modern views of horse breeding. King Philip II’s survey of horse breeding in Spain and his efforts to develop a new royal “race” (raza) of horses provide two valuable case studies of contemporary debates about improving horse breeds. Knowledge and expertise gained from active horse breeding often contradicted ideal values of lineage or blood purity. These cases acknowledge limits to the control implied in selectively breeding domesticated animals and demonstrate an early modern understanding of the contructedness of horse breeds. In a larger sense, these findings offer a nuanced reading of how raza and casta in animal husbandry relate to histories of racial terminology and classifications of difference in the Spanish empire.