Abstract: An extruded, one-piece metal slat unit for attachment to a frame member of a trailer. The slat unit includes an elongated body portion having at least one leg member connected to and longitudinally extending along the interior surface of the body portion between the ends thereof. The leg member includes a foot portion suitable for welding to the frame member. The foot portion is spaced from the interior surface of the body portion such that an open space is provided therebetween. The open space dissipates heat generated during the welding process thereby preventing nonaesthetic weld and heat track marks from appearing on the exterior surface of the slat unit and hence the trailer. A livestock trailer including the slat unit is also provided.