  We examine the minimal supergravity (mSUGRA) model under the assumption that
the strong CP problem is solved by the Peccei-Quinn mechanism. In this case,
the relic dark matter (DM) abundance consists of three components: {\it i}).
cold axions, {\it ii}). warm axinos from neutralino decay, and {\it iii}). cold
or warm thermally produced axinos. To sustain a high enough re-heat temperature
(T_R\agt 10^6 GeV) for many baryogenesis mechanisms to function, we find that
the bulk of DM should consist of cold axions, while the admixture of cold and
warm axinos should be rather slight, with a very light axino of mass \sim 100
keV. For mSUGRA with mainly axion cold DM (CDM), the most DM-preferred
parameter space regions are precisely those which are least preferred in the
case of neutralino DM. Thus, rather different SUSY signatures are expected at
the LHC in the case of mSUGRA with mainly axion CDM, as compared to mSUGRA with
neutralino CDM.
