A farrowing pen having a floor which has a perimeter area and a central area, the central area having a plurality of elongated flooring members spaced apart with at least one slat extending between each of the elongated flooring members, and a biased retaining apparatus for urging slats into a position wherein at least a portion of the slats are above the generally horizontal plane of the floor to thereby provide a flooring surface in the central portion having a ribbed effect. The ribbed floor will discourage the sow from lying down and thus crushing the piglets.