  We calculate the spectrum of energy loss differences due to gluon radiation
in high energy hard forward processes in proton-nucleus collisions as compared
to proton-proton collisions. We find that the nuclear induced energy loss
scales linearly with the beam energy. We evaluate the spectrum and "typical"
energy losses in a logarithmic and large $N_{c}$ approximation. The energy
losses found appear large enough to be phenomenologically important.
