A trailer includes a chassis and a body connected to the chassis. The body includes an open-top cargo-retaining space adapted to carry a bulk commodity payload. An axle subassembly is connected to the chassis and includes at least one set of left and right wheel and tire assemblies to rollably support the chassis. A landing gear assembly is connected to one or both of the chassis and body and includes legs that are selectively deployed to support a forward end of the trailer. A kingpin is located at the forward end of the trailer and is adapted for connection to a fifth-wheel of an associated vehicle used to pull the trailer. The body includes left and right bottom rails and left and right top rails spaced vertically above the left and right bottom rails, respectively. A horizontal floor extends between the left and right bottom rails. The floor includes a plurality of abutted one-piece extruded panels that each extend horizontally between and contact the left bottom rail and the right bottom rail. Each of the extruded panels includes spaced-apart inner and outer walls interconnected by spaced-apart first and second end walls. The inner and outer walls are also interconnected by at least one web that spans a space between the inner and outer walls so as to define at least two hollow cores in the extruded panel. A left vertical sidewall is connected to and extends between the left bottom rail and the left top rail. A right vertical sidewall is connected to and extends between the right bottom rail and the right top rail.