  We present one-loop results for the forward twist-two matrix elements
relevant to the unpolarised, helicity and transversity baryon structure
functions, in partially-quenched (N_f=2 and N_f=2+1) heavy baryon chiral
perturbation theory. The full-QCD limit can be straightforwardly obtained from
these results and we also consider SU(2|2) quenched QCD. Our calculations are
performed in finite volume as well as in infinite volume. We discuss features
of lattice simulations and investigate finite volume effects in detail. We find
that volume effects are not negligible, typically around 5--10% in current
partially-quenched and full QCD calculations, and are possibly larger in
quenched QCD. Extensions to the off-forward matrix elements and potential
difficulties that occur there are also discussed.
