Close to sinusoidal substrates, simple fluids may undergo a filling
transition, in which the fluid passes from a dry to a filled state, where the
interface remains unbent but bound to the substrate. Increasing the surface
field, the interface unbinds and a wetting transition occurs. We show that this
double-transition sequence may be strongly modified in the case of ordered
fluids, such as nematic liquid crystals. Depending on the preferred orientation
of the nematic molecules at the structured substrate and at the
isotropic-nematic interface, the filling transition may not exist, and the
fluid passes directly from a dry to a complete-wet state, with the interface
far from the substrate. More interestingly, in other situations, the complete
wetting transition may be prevented, and the fluid passes from a dry to a
filled state, and remains in this configuration, with the interface always
attached to the substrate, even for very large surface fields. Both transitions
are only observed for a same substrate in a narrow range of amplitudes
