  We study the distribution of the star formation rate and metallicity of
damped Lyman-alpha absorbers using cosmological SPH simulations of the Lambda
cold dark matter model in the redshift range z=0-4.5. Our approach includes a
phenomenological model of galactic wind. We find that there is a positive
correlation between the projected stellar mass density and the neutral hydrogen
column density (NHI) of DLAs for high NHI systems, and that there is a good
correspondence in the spatial distribution of stars and DLAs in the
simulations. The evolution of typical star-to-gas mass ratios in DLAs can be
characterised by an increase from about 2 at z=4.5 to 3 at z=3, to 10 at z=1,
and finally to 20 at z=0. We also find that the projected SFR density in DLAs
follows the Kennicutt law well at all redshifts, and the simulated values are
consistent with the recent observational estimates of this quantity by Wolfe et
al. (2003a,b). The rate of evolution in the mean metallicity of simulated DLAs
as a function of redshift is mild, and is consistent with the rate estimated
from observations. The predicted metallicity of DLAs is generally sub-solar in
our simulations, and there is a significant scatter in the distribution of DLA
metallicity for a given NHI. However, we find that the median metallicity of
simulated DLAs is close to that of Lyman-break galaxies, which is higher than
the values typically observed for DLAs by nearly an order of magnitude. This
discrepancy with observations could be due to an inadequate treatment of SN
feedback in our current simulations, perhaps indicating that metals are not
expelled efficiently enough from DLAs by outflows. Alternatively, the current
observations might be missing the majority of the high metallicity DLAs due to
selection effects. (abridged)
