Reproductive hormone secretion and testicular growth in bull calves actively immunized against testosterone and oestradiol-17β

A motor has a motor gear installed in a motor output shaft to rotate in synchronization. A gearshift actuation transmission mechanism has a gear shift cam-side actuator gear directly engaged with a gear shift cam to transmit rotation. The gear shift cam-side actuator gear meshes with the motor gear directly or indirectly by interposing another actuator gear to transmit the rotation from the motor to the gear shift cam.