A treatment device for treating cut fodder includes a treatment rotor, first and second supports, and a driving device for driving the treatment rotor. The first support of the treatment device is located near a first end of the treatment rotor. The first support includes a first bearing in which the first end of the treatment rotor is guided in its rotation. The driving device includes a transmission device. The transmission device includes a first and second wheels, at least one endless transmission member, and a regulating or adjusting mechanism for regulating or adjusting the tension in the at least one endless transmission member. The second wheel of the transmission device is mounted on the first end of the treatment rotor. The at least one endless transmission member is wound around both the first and second wheels of the transmission device. The treatment device for treating cut fodder is characterized in that the regulating or adjusting mechanism for adjusting the tension in the endless transmission member includes the first bearing of the first support of the treatment device and the second wheel of the transmission device such that both the first bearing and the second wheel can be moved away from the first wheel of the transmission device in order to arrive at a desired position of adjustment. The regulating or adjusting mechanism also includes a retaining device for retaining the first bearing and the second wheel in the desired position of adjustment. The retaining device includes a tensioning member.