  We study the kinetics of antibaryon production and annihilation in an
expanding system, assuming that it is spatially homogeneous and chemically
equilibrated at the initial stage. By solving simplified rate equations for
(anti)baryon abundances we study the deviations from chemical equilibrium at
late stages. The calculations are done for different expansion rates and
net-baryon-to-entropy ratios, covering the conditions from early Universe to
heavy-ion collisions. Our analysis includes both stable (anti)baryons and
resonances. We conclude that residual antibaryon abundances are very sensitive
to the time scales of expansion. Our calculations naturally explain noticeable
deviations of antiproton-to-pion and proton-to-pion ratios observed in nuclear
collisions at the LHC energy from the thermal model predictions. We conclude
that at high bombarding energies the chemical freeze-out of (anti)baryons
should occur at lower temperatures as compared to mesons.
