  The LHCb experiment covers a unique region of acceptance at forward
rapidities in the high energy proton-proton collisions of the LHC. This means
that measurements of particle production in LHCb are directly sensitive to the
parton distribution functions at low Bj\"orken-$x$ values. Several measurements
of inclusive $W$ and $Z/\gamma^{\ast}$ production with the Run-I dataset are
reported in these proceedings. Further measurements of $W$ and
$Z/\gamma^{\ast}$ production in association with inclusive jets and $b$- and
$c$-tagged jets are also reported.
