  The periodic orbit conjecture states that, on closed manifolds, the set of
lengths of the orbits of a non-vanishing vector field all whose orbits are
closed admits an upper bound. This conjecture is known to be false in general
due to a counterexample by Sullivan. However, it is satisfied under the
geometric condition of being geodesible. In this note, we use the recent
characterization of Eulerisable flows (or more generally flows admitting a
strongly adapted one-form) to prove that the conjecture remains true for this
larger class of vector fields.
