  We study low energy experimental constraints on an anomalous top-quark
coupling associated with the flavor-changing neutral current vertex $Z \bar t
c$. In view of these constraints, we discuss the experimental observability of
the induced rare decay mode $t \rightarrow Zc$, both at the Fermilab Tevatron
(with the Main Injector or a luminosity-upgrade) and at the LHC.
