  Diboson production ($WW+WZ+ZZ$) has been observed at the Tevatron in hadronic
decay modes dominated by the $WW$ process. This paper describes the measurement
of the cross section of $WZ$ and $ZZ$ events in final states with large $\mett$
and using $b$-jet identification as a tool to suppress $WW$ contributions. Due
to the limited energy resolution, we cannot distinguish between partially
hadronic decays of $WZ$ and $ZZ$, and we measure the sum of these processes.
The number of signal events is extracted using a simultaneous fit to the
invariant mass distribution of the two jets for events with two $b$-jet
candidates and events without two $b$-jet candidates. We measure a cross
section $\sigma(p\bar{p}\to WZ,ZZ) = 5.8^{+3.6}_{-3.0}$ pb, in agreement with
the standard model.
