From chapter two, "The Soldier", by Geoffrey Parker, from Rosario Villari's Baroque Personae:

"in the first decades of the [seventeenth] century, it is true, cavalry made up less than 10 percent of most armies in Western Europe: when France went to war against Spain in 1635, orders were issued to raise 132,00 infantry but only 12,400 cavalry. Yet even this relatively small total continued to pose supply problems, since each cavalry trooper would need at least three mounts in the course of a campaign ... and sometimes more: at the battle of Breitenfeld in 1631, the Tuscan officer Ottavio Piccolomini had seven horses shot from under him in the course of a day."