If your extrude is a single object then texture has been applied to the ends .... just not mapped properly to it.
In vertex mode, hilite one end of the object, open the Texture Editor (Tools Menu), and select the outline then map to top. Repeat for the bottom.
I assume that sides are facing you and the ends are top and bottom in the Front view. If the ends are facing you ... then remap them to Front instead.
Note: If the bottom of the object rests on the floor and will not be seen, hilite the vertices then Surface--> Cut Away Object and delete it. Also if an enclosed object and inside will not be seen ... make it single sided
griff