A hydraulic ram comprising a fixed support, a cylinder that is movable in translation relative to the support, a piston secured inside the cylinder delimiting two chambers with the cylinder and a device for supplying the chambers with hydraulic fluid upstream from the fixed support. The ram is characterized by the fact that the supply device comprises telescopic channels, each telescopic channel comprising two tubular elements sliding one into the other, a first tubular element being rigidly connected to the fixed support at one end and the second tubular element being rigidly connected to the cylinder at at least two points separated from each other along a generatrix of the cylinder. The invention is applicable to controlling the pitch of the blades of a turbine engine propeller.