Patent ID: 8734430

Claim:
A sustained release capsule comprising: a) a hollow tubular body sealed at a first end, b) a movable piston within the body, c) a spring biasing the piston towards a second end of the body, d) an apertured cover at the second end to define a first chamber between the movable piston and the apertured cover capable of containing a first dose of material within the hollow tubular body for subsequent sustained release through the apertured cover into a rumen of an animal, and wherein the movable piston has an end face facing towards the first dose, a hollow central sleeve extending rearwardly from the end face to assist in locating a spring, an aperture in the end face into a hollow interior of the central sleeve, the central sleeve having a closed portion distal from the end face to create a void capable of containing an exit dose of material.