An apparatus for feeding a fiber batt to a fiber processing machine includes a rotatably supported feed roll; a feed table having a face portion cooperating with the feed roll and defining therewith a nip through which the fiber batt passes in an advancing direction; an arrangement rendering at least one part of a feed table surface wear resistant which directly contacts the fiber batt upon passage thereof; a movably supported elongated holding element extending spaced from, and generally parallel to the feed roll; and a plurality of sensor elements each being affixed to the holding element and each being arranged to undergo excursions as a function of thickness variations of the fiber batt passing through the nip. The sensor elements impart a displacing force on the holding element which moves to an extent representing a sum of the displacing forces. A sensor arrangement is connected to the holding element for generating a signal as a function of displacements of the holding element.