An animal confinement pen flooring system, particularly adapted for swine farrowing operations, includes at least first and third rows of spaced-apart molded plastic foraminous flooring panels and an intermediate row of cast iron foraminous flooring panels, all of the panels being supported on spaced-apart elongated support rails in a stand off position above a subfloor. The plastic and cast iron panels each include opposed sets of hooked-shaped flanges for engagement with support rails, respectively, for supporting the panels thereon. The cast iron panels each include a boss and an opposed recess disposed on opposite sides thereof for interconnecting adjacent panels by cooperating hook portions formed on the boss and in the recess of the adjacent panel, respectively. The combination of the cast iron and molded plastic flooring panels provides enhanced comfort for swine in farrowing operations.