An apparatus for injecting a liquid into live animals, comprising a cradle plate (18) having a cradle (24) for accommodating at least a part of an animal, sensors (20-1, 20-2, 20-3) for detecting a force acting upon the cradle plate, an injection mechanism (16) for injecting liquid into the animal, and a control unit (38) for triggering the injection mechanism (16) in response to signals received from the sensors, wherein at least three sensors (20-1-, 20-2, 20-3) are arranged for measuring forces with which the cradle plate (18) is pressed against a base (12) in at least three non-aligned positions, and the control unit (38) is adapted to trigger the injection mechanism (16) when the forces measured by the sensors are distributed according to a predetermined pattern.