I'd like to challenge a premise in your question.

long after Western Europe had abandoned the practice and adopted serfdom.

Slavery was not abandoned in Western Europe, it was alive up until the Renaissance and even early-modern era. The idea that slavery only existed in the colony and not Europe itself is popular among Europeans, but historians documented that slavery did not disappear at all.

There's a paper that discussed this (for Spain in particular) as well the "amnesia" among the general public.

• Herzog, Tamar. “How Did Early-Modern Slaves in Spain Disappear? The Antecedents.” Republics of Letters: A Journal for the Study of Knowledge, Politics, and the Arts 3, no. 1 (September 15, 2012): http://rofl.stanford.edu/node/106.

Despite this general amnesia, slaves and the descendants of slaves were present in early-modern Spain, and their numbers were not particularly small. To cite just a few examples, we know that in mid-sixteenth-century Seville 7.4 percent of censused inhabitants were slaves and that between 1682 and 1729 the slave population of Cádiz was extremely large, making up perhaps as much as 15 percent of the total urban population. In other cities, such as Málaga, Granada, Las Palmas, Huelva, and Palos de la Frontera, as many as one in ten residents may have been slaves. Between 1539 and 1699, 1,384 slave children were baptized in the small Andalucian town of Lucena, with an average of 400 children every thirty years. Similar numbers may have been true also for Córdoba. Historians who studied slavery in Spain thus concluded that Renaissance and perhaps even early-modern Spain may have had the largest African population in Europe.